radiating branched processes spread mainly parallel to the retinal plane, lar and rely on an indirect supply from the choroidal capillaries. The
giving them a star-like appearance when viewed microscopically from inner retina receives a direct blood supply through capillaries connected
the surface of the retina. They can act as phagocytes, and their number to branches of the central retinal artery and vein. Only the inner retinal
increases in the injured retina. circulation is described here.
The inner border of the retina is formed by the internal limiting The central retinal artery enters the optic nerve as a branch of the
membrane (layer 10), which consists of collagen fibres and proteo- ophthalmic artery 6.4–15.2 mm behind the eyeball (Kocabiyik et al
glycans from the vitreous, a basement membrane (which is continuous 2005), and travels within the optic nerve to its head, where it passes
with the basal lamina of the ciliary epithelium), and the plasma mem- through the lamina cribrosa. At this level, the central artery divides into
brane of expanded Müller cell terminal foot plates. It is 0.5–2 µm thick equal superior and inferior branches, which, after a few millimetres,
in the posterior retina and thickens with age. The internal limiting divide into superior and inferior nasal, and superior and inferior tem-
membrane is involved in fluid exchange between the vitreous and the poral, branches, each supplying a ‘quadrant’ of the retina (see Fig.
retina, and, perhaps through the latter, with the choroid. It also has 42.27). Although similar retinal veins unite to form the central retinal
various other functions, including anchorage of retinal glial cells, and vein, the courses of the arteries and veins do not correspond exactly.
inhibition of cell migration into the vitreous body. These vessels mainly run within the nerve fibre and ganglion cell layers
of the retina, accounting for their clarity when seen through an oph-
thalmoscope (see Fig. 42.20A). Arteries often cross veins, usually lying
Modifications of the central retina
superficial to them; in severe hypertension, the arteries may press on
the veins and cause visible dilations distal to these crossings. The vitreal


The central retina, clinically referred to as the macula, is composed of location of arteries, their lighter, bright red colouration and smaller
four concentric areas, which, starting with the innermost, are: the diameter in comparison to veins allow the two vessel types to be dis-
foveola (0.35 mm diameter, equivalent of an angular subtense at the tinguished ophthalmoscopically.
nodal point of around 1.25°), the fovea (1.5 mm, 5.2°), the parafovea From the four major arteries within the inner retina, dichotomous
(2.5 mm, 8.6°) and the vaguely defined perifovea (5–6 mm, 20°). The branches run from the posterior pole to the periphery, supplying the
foveola, which contains no rods or S cones, is centred about 3 mm whole retina (Zhang 1994). Arteries and veins ramify in the nerve fibre
temporal and 1 mm inferior to the optic disc (see Fig. 42.20A). In the layer, near the internal limiting membrane, and arterioles pass deeper
foveola and surrounding fovea, all the inner layers of the neural retina into the retina to supply capillary beds. Venules return from these beds
beyond the outer nuclear layer have been displaced peripherally, result- to larger superficial veins that converge towards the disc to form the
ing in a retinal thickness around half of that elsewhere in the retina (see central retinal vein.
Fig. 42.23; Fig. 42.28). This foveal pit is created by the cone ‘axons’, Retinal capillary networks can occur in three different layers, the
known here as Henle fibres, running almost parallel to the retinal number of layers depending on location (Zhang 1994). Radial peri-
surface before connecting to postreceptoral retinal neurones outside the papillary capillaries are the most superficial of the capillary networks


Retina
705
24
RETPAHC
and lie within the inner nerve fibre layer. A layer of inner capillaries The adrenergic postganglionic sympathetic supply originates in the
runs within the nerve fibre and ganglion cell layers, while an outer superior cervical ganglion and travels via a plexus around the internal
capillary layer is located in the inner plexiform and inner nuclear layers carotid and ophthalmic arteries; it is unclear whether it elicits vasocon-
(Fig. 42.29). Approaching the fovea, capillaries are restricted to two striction or dilation (Bergua et al 2013).
layers, and terminal capillaries eventually join to form a single-layered
macular capillary ring, producing a capillary-free zone 450–500 µm in
diameter at the fovea. This avascular region is clearly visible in a fluo- RETINOPETAL INNERVATION OF THE RETINA
rescein angiogram (Fig. 42.20B). Capillaries become less numerous in
the peripheral retina and are absent from a zone approximately 1.5 mm The human retina receives input from the brain via retinopetal axons
wide adjoining the ora serrata. within the optic nerve. Although there are only a small number of these
The territories of the arteries that supply a particular quadrant do (usually less than 10), they branch extensively within the retina. They
not overlap, nor do the branches within a quadrant anastomose with emerge at the optic disc, course through the nerve fibre layer, and give
each other; consequently, a blockage in a retinal artery causes loss of off orthogonal branches that ramify in the inner plexiform layer
vision in the corresponding part of the visual field. The only exception (Repérant et al 2006). One set of such axons arises from perikarya in
to this end-arterial pattern is in the vicinity of the optic disc. Here, the the posterior hypothalamus and uses histamine as a neurotransmitter,
posterior ciliary arteries enter the eye near the disc (Fig. 42.30), and while other, serotoninergic, fibres arise from cell bodies in the dorsal
their rami not only supply the adjacent choroid, but also form an raphe. These neurones are not specialized for vision; they project to


anastomotic circle in the sclera around the head of the optic nerve. many other targets in the central nervous system besides the retina,
Branches from this ring join the pial arteries of the nerve, and small forming components of an ascending arousal system (Gastinger et al
cilioretinal arteries from any arteries in this region may enter the eye 2006). Histamine is released during the day in the inner plexiform layer,
and contribute to the retinal vasculature, possibly resulting in the pres- but it activates receptors located on cone pedicles, horizontal cell peri-
ervation of visual function following central retinal artery occlusion. karya and ON bipolar cell dendrites via volume transmission. Hista-
Similarly, small retinociliary veins may sometimes also be present. mine decreases the absolute sensitivity of the retina to light and,
The structure of retinal blood vessels resembles that of vessels else- possibly, modulates retinal blood flow (Vila et al 2012).
where, except that the internal elastic lamina is absent from the arteries,
and muscle cells may appear in their adventitia. Capillaries are non-
OPTIC NERVE HEAD
fenestrated and endothelial cells are joined by complex tight junctions,
fulfilling the requirements of a functional blood–retinal barrier. Within
the optic nerve, the central artery is innervated by both branches of the The axons of more than a million retinal ganglion cells converge at the
autonomic nervous system; this innervation does not extend to the optic nerve head and leave the eye by penetrating the sclera to form the
vessels in the retina. The cholinergic parasympathetic supply is derived optic nerve. The optic nerve head represents that part of the optic nerve
mainly from the pterygopalatine ganglion and is vasodilatory (Ch. 32). lying within the bulb of the eye. Since all retinal neural elements, apart
from ganglion cell axons, are absent from this region, it is insensitive
to light and forms the ‘blind spot’.
Histologically, the optic nerve head can be divided into three zones
(Fig. 42.31): the prelaminar (the anterior part terminating at the vitre-
ous), laminar (formed by the lamina cribrosa) and postlaminar (con-
tinuous with the retrobulbar optic nerve). The surface view of the optic


nerve head, usually seen with an ophthalmoscope, is referred to as the
optic disc (Fig. 42.20).
Prelaminar zone
The inner surface of the optic nerve head is covered by an astroglial
membrane (of Elschnig) that is continuous with the internal limiting
membrane of the retina. At the centre of the disc, the layer of astrocytes
thickens into a central meniscus (of Kuhnt). Retinal ganglion cells turn
into the optic nerve head accompanied by astrocytes, which gradually
increase in number posteriorly, eventually forming a sieve-like structure,
the glial lamina cribrosa, through which the nerve fibres pass as separate
fasciculi. At the perimeter of the optic nerve head, a collar of astrocytes
several cells thick (the intermediary tissue of Kuhnt) separates the optic
nerve from the terminating outer layers of the retina. This layer contin-
Fig. 42.29 A tangential section of the retina at the level of the inner ues posteriorly and forms a barrier between the optic nerve head and
nuclear layer, highlighting the dense network of capillaries. the choroid (the border tissue of Jacoby).
Fig. 42.30 Vessels of the optic nerve head.
The dotted areas represent the principal glial
Retina
membranes. Arteries are represented on the right
Choroid and veins on the left.
Sclera
Circle of Zinn/Haller
Short posterior
ciliary artery
Lamina Central canal of Arachnoid mater
cribrosa the optic nerve
Central retinal Central retinal Pia mater Dura mater
vein artery


EYE
706
4
NOITCES
1b
1a
2 Retina
5
Choroid
3 4
6
Sclera
Circle of Zinn
7
Sep
Sep
Du
Ar GI.M
Pia GI.C
Fig. 42.31 The optic nerve head, showing the distribution of collagenous tissue (grey) and neuroglial nuclei (solid blue circles). Key: 1a, retinal internal
limiting membrane; 1b, inner limiting membrane of Elschnig; 2, central meniscus of Kuhnt; 3, spur of collagenous tissue separating the anterior lamina
cribrosa (6) from the choroid; 4, border tissue of Jacoby; 5, intermediary tissue of Kuhnt; 7, posterior lamina cribrosa. Abbreviations: Ar, arachnoid mater;
Du, dura mater; Gl.C, astrocytes and oligodendrocytes among the fibres in their fascicles; Gl.M, astroglial membrane; Pia, pia mater; Sep, connective
tissue septa from pia mater. The dotted lines represent the borders of the lamina cribrosa. (With permission from Anderson DR, Hoyt W 1969
Ultrastructure of intraorbital portion of human and monkey optic nerve. Arch Ophthalmol 82:506–30.)
Laminar zone general retinal hue is a bright terracotta-red, with which the pale pink
of the disc contrasts sharply; its central part is usually even paler and
may be light grey. These differences are due in part to the degree of
The lamina cribrosa is composed of discrete trabeculae of collagenous
vascularization of the two regions, which is much less at the optic disc,
and elastic connective tissue, which extend from the sclera to form a
and also to the total absence of choroidal or retinal pigment cells. In
meshwork through which the optic nerve fascicles and central retinal
subjects with strongly melanized skins, both retina and disc are darker.
vessels pass. Each trabecula has a lining of astrocytes that are continu-
The optic disc rarely projects sufficiently to justify the term papilla,
ous with those of the glial lamina cribrosa.
although it is usually a little elevated on its lateral side, where the


papillomacular nerve fibres turn into the optic nerve (see Fig. 42.27).
Postlaminar zone
There is usually a slight depression where the retinal vessels traverse its
centre.
The optic nerve thickens in the postlaminar zone as its axons become
myelinated. The reflected sclera, and the dura mater with which it is Vascular supply
continuous, invest the nerve together with the other two meningeal
sheaths, the arachnoid and pia mater. Fine fibrous septa penetrate the
The blood supply to the three regions of the optic nerve head differs
optic nerve from the pia mater, dividing it into 300–400 fascicles, giving
(see Fig. 42.30). The prelaminar region is supplied mainly by branches
pial blood vessels access to the nerve.
of the central retinal artery. Branches from the short posterior ciliary
arteries form an often incomplete circle within the sclera around the
Optic disc
optic nerve head (circle of Zinn/Haller); centripetal branches from this
structure supply the laminar region of the optic nerve head. The short
As it is visible by ophthalmoscopy (see Fig. 42.20A), the disc is a region posterior ciliary arteries may also give off centripetal branches directly
of great clinical importance. Oedema of the disc (papilloedema) may to supply the lamina, and branches that pass anteriorly to augment the
be the first sign of raised intracranial pressure, which is transmitted into prelaminar blood supply. In the postlaminar region, arteries from the
the subarachnoid space around the optic nerve. The disc is also sensitive prepapillary choroid and circle of Zinn pass retrogradely as pial vessels,
to the raised intraocular pressure that occurs in glaucoma and shows providing centripetal branches that supply the optic nerve. More poste-
characteristic structural changes due to retinal ganglion cell loss. riorly, the optic nerve receives pial arterioles directly from the posterior
The optic disc is superomedial to the posterior pole of the eye, and ciliary arteries. The central retinal artery may also contribute some
so lies away from the visual axis. It is round or oval, and usually centrifugal branches in this region.


approximately 1.6 mm in transverse diameter and 1.8 mm in vertical The central retinal vein drains the optic nerve head at all levels; other
diameter; its appearance is very variable. In light-skinned subjects, the drainage pathways are minor.


Visual pathway
707
24
RETPAHC
Left visual field Binocular field Right visual field Fig. 42.32 A simplification of the visual pathway,
showing the spatial arrangement of neurones and
their fibres in relation to the quadrants of the
retinae and visual fields. The proportions at
various levels are not exactly to scale. In
particular, the macula is exaggerated in size in the
visual fields and retinae. In each quadrant of the
visual field, and in the parts of the visual pathway
subserving it, two shades of each respective
Left Binocular Right
monocular monocular Note optical colour are used; the paler shade denotes the
inversion peripheral field and the darker shade denotes the
macular part of the quadrant. From the lateral
geniculate nucleus onwards, these two shades are
Right both made more saturated to denote intermixture
retina
of neurones from both retinae, the palest shade
being reserved for parts of the visual pathway
concerned with monocular vision.
Macula
Optic
nerve
Chiasma
Lateral
geniculate
nucleus
Visual
cortex
Optic
radiation
developing earlier during axogenesis than the more superficial ones
VISUAL PATHWAY
(Reese 1993).
The lateral geniculate nucleus contains cells arranged in six laminae
The visual pathway includes the interneurones of the retina, retinal (see Fig. 23.6). Each layer receives input from either crossed or uncrossed
ganglion cells whose axons project via the optic nerve, chiasma, and projections from the retina. The contralateral nasal retina projects to
optic tract to the lateral geniculate nucleus and neurones within the laminae 1, 4 and 6, whereas the ipsilateral temporal retina projects to
lateral geniculate nucleus that project via the optic radiation to the layers 2, 3 and 5. Layers 1 and 2 contain magnocellular cells; the
primary visual cortex (Fig. 42.32). It is important to remember that remaining layers are parvocellular. Unlike in the optic tract, there is a
visual space is optically inverted by the crystalline lens when relating point-to-point retinotopic arrangement between corresponding points


the spatial location of neurones within the visual pathway to corres- in each hemi-retina so that the contralateral visual field is mapped
ponding visual field locations. within each lateral geniculate nucleus.
Retinal ganglion cell axons, on entering the optic nerve, initially Axons from the lateral geniculate nucleus run in the retrolenticular
maintain their relative retinal positions, with axons from the fovea part of the internal capsule and form the optic radiation. This curves
forming a lateral wedge. Such retinotopic mapping is largely main- dorsomedially to the primary visual cortex, located around and within
tained within the optic nerve, although nearer the chiasma the foveal the depths of the calcarine sulcus in the occipital lobe (also known as
axons take a position in the centre of the optic nerve while temporal the striate cortex, Brodmann area 17, or V1 (see Fig. 25.19). The visual
fibres occupy their previous lateral location. cortex also has a strict retinotopic organization. Fibres representing the
At the chiasma, a substantial rearrangement of axons occurs. Most lower half of the visual field sweep superiorly to reach the visual cortex
axons arising from the nasal half of a line bisecting the fovea within above the calcarine sulcus, while those representing the upper half of
each retina cross in the chiasma to enter the contralateral optic tract. the visual field curve inferiorly into the temporal lobe (Meyer’s loop)
Fibres from the temporal hemi-retinas do not generally cross in the before reaching the visual cortex below the calcarine sulcus. The
chiasma. Classically, the axons within the optic tract were thought to periphery of the retina is represented anteriorly within the visual
maintain their topographic order and each tract was assumed to be a cortex, and the macula is represented towards the posterior pole, occu-
single representation of the contralateral hemifield. However, it is now pying a disproportionately large area that reflects the high number of
clear that axons are mainly organized in functional groupings, larger foveal retinal ganglion cells that subserve the enhanced acuity of this
superficial axons representing the magnocellular pathway and deeper region.


axons originating from midget ganglion cells and forming the parvo- The primary visual cortex is connected to prestriate and other cortical
cellular pathway. This arrangement is chronotopic, the deeper axons regions where further processing of visual stimuli occurs.


EYE
708
4
NOITCES
Almost all of the retinal ganglion cell axons (90%) terminate on Since the optic tract contains contralateral nasal and ipsilateral tem-
neurones in the lateral geniculate nucleus. Extrageniculate axons (10%) poral retinal projections, damage to it will cause a homonymous con-
leave the optic tract before the lateral geniculate nucleus; they may leave tralateral visual field loss. Although complete disruption of the tract
the optic chiasma dorsally and project to the suprachiasmatic nucleus results in contralateral hemianopia, the incomplete spatial segregation
of the hypothalamus, while others branch off the optic tract at the of axons within the tract, described above, makes the field losses fol-
superior brachium and project to the superior colliculus, pretectal areas lowing smaller lesions harder to interpret. They do, however, show
and inferior pulvinar. substantial incongruity (dissimilar defects in the fields of the two eyes)
and often specific functional deficits, consistent with the partial segrega-
tion of functionally distinct axons from the two half-retinas (Reese
VISUAL FIELD DEFECTS 1993). Incongruity is most marked in defects of the optic tract, less
obvious in optic radiation defects, and usually absent in cortically
The basis for clinical assessment of damage to the visual pathway is an induced field defects, thus providing an additional clue in assessing
understanding of the retinotopic projections within the pathway. More- location of the cause.
over, plotting visual field loss frequently reveals the approximate loca- Lesions of the optic radiations are usually unilateral, and commonly
tion of the causative lesion and sometimes its nature. Since retinal vascular in origin. Field defects therefore develop abruptly, in contrast
lesions can be visualized with an ophthalmoscope, field testing might to the slow progression of defects associated with tumours, and the
appear to be redundant for such defects, but visual field measurement resulting hemifield loss follows the general rule that visual field defects
is still helpful in assessing the extent of the damage and may be the key central to the chiasma are on the opposite side to the lesion. Little or
factor in confirming a diagnosis. Field defects in glaucoma, for example, no incongruity is seen in visual cortical lesions, but they commonly


that occur as a consequence of damage to the nerve fibre bundles at the display the phenomenon of macular sparing, the central 5–10° field
optic nerve head, may be detectable ophthalmoscopically, but confir- being retained in an otherwise hemianopic defect.
mation of the diagnosis frequently depends on field assessment. Early
defects consist of one or more areas of paracentral focal field loss, pro-
gressing to arcuate scotomas. The shape of the defect corresponds to
the anatomical arrangement of ganglion cell axons. Bonus e-book image
As far as the location of lesions central to the retina is concerned,
deficits in the vision of one eye are usually attributable to optic nerve
lesions. Lesions of the optic chiasma, involving crossing nerve fibres, Fig. 42.20B Fluorescein angiogram showing the macular region of
produce a bilateral field loss, as exemplified by a pituitary adenoma. a right eye. The main macular vessels are approaching from the
The tumour expands upwards from the pituitary fossa, compressing the right. The subject was an elderly person with considerable macular
inferior midline of the chiasma, and eventually produces bitemporal pigmentation, which masks fluorescence from the choroidal
hemianopia, starting with an early loss in the upper temporal quadrants circulation.
(bitemporal quadrantanopia).
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A summary of the various mechanisms of accommodation and the reasons role in various disease processes.
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Wallman J, Winawer J 2004 Homeostasis of eye growth and the question of
Curcio CA, Sloan KR, Kalina RE et al 1990 Human photoreceptor topogra- myopia. Neuron 43:447–68.
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The first description of the distribution of rods and cones in the human
Wang D, Qi M, He M et al 2012 Ethnic differences of anterior chamber area
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RETPAHC
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53:7813–18. The most comprehensive description of the morphology of neural cell types in
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receptors. Physiology 25:8–15.


COMMENTARY
4.1
Surgery of the skull base
Juan C Fernandez-Miranda
Accessing the skull base for removal of complex lesions is a formidable (Alaywan and Sindou 1990). This middle fossa approach can also be
challenge. Accurate knowledge of the intricate osseous, dural and used to open the roof of the internal acoustic canal, and can be extended
neurovascular anatomy is mandatory to perform a successful cranial to the posterior fossa by drilling out the petrous apex that forms the
base operation and restore or preserve normal structure and function posteromedial triangle of the middle fossa (Kawase et al 1985).
(Rhoton 2007). Lesions involving the base of the skull are most com
monly tumours, which are classified based on their origin: meningi Approaches to the posterior cranial fossa
omas (from meninges), adenomas (from pituitary gland cells),
schwannomas (from nerve sheath cells), chondrosarcomas (from carti
The posterior cranial fossa is formed by the sphenoid, temporal and
lage cells), chordomas (from notochordal remnant cells), esthesioneuro
occipital bones, and contains the cerebellum, pons and medulla oblon
blastomas (from olfactory cells), and others.
gata (see Figs 16.5, 28.2). The suboccipital approach is a posterior
Surgical approaches to the skull base can be divided, based on the
midline approach that consists of removing part of the occipital squama
location of the targeted lesion, into three broad categories: anterior,
and posterior arch of foramen magnum to provide access to bilateral
middle and posterior skull base approaches. Certain lesions may involve
cerebellar hemispheres and the posterior cervicomedullary junction.
more than one cranial fossa, and therefore the cranial base approach
The retrosigmoid craniectomy is a posterolateral approach that entails
for that particular lesion will have to be either extended or comple
completion of a bony window located just behind the sigmoid sinus
mented with another approach. As a general principle, skull base
and just inferior to the transverse sinus; it provides access to the cerebel
approaches are designed to minimize trauma to neural tissues and at


lopontine angle, as typically required for vestibular schwanommas and
the same time maximize access to the target lesion, following the rule
for microvascular decompression for treatment of trigeminal neuralgia
of ‘maximal bone removal for minimal brain manipulation’. They com
or hemifacial spasm. Both suboccipital and retrosigmoid approaches
prise several sequential steps: tailored skin incision; dissection of mus
can be augmented with full removal of the posterior arch of the foramen
cular and fascial planes; completion of craniotomy, osteotomies, and
magnum, including part of the occipital condyle. This modification is
drilling of osseous structures as needed; extradural approach to the
called the far lateral transcondylar approach, and is used to obtain a
target lesion, when feasible, to avoid unnecessary brain retraction and
better trajectory into the ventral aspect of the lower clival region and
facilitate early devascularization of the lesion; intradural approach, if
cervicomedullary junction (Wen et al 1997). The mastoid bone can also
needed, with microsurgical dissection of arachnoid cisterns, preser
be drilled in front of the sigmoid sinus to complete a presigmoid
vation of neurovascular structures, and lesion removal; meticulous
approach, which provides access to the labyrinthine, middle ear cavity,
haemostasis; dural closure (primary or using grafts or patches); osseous
facial nerve canal and jugular foramen; opening of the presigmoid dura
reconstruction; and fascial, muscular and skin reapproximation.
will directly expose the cerebellopontine angle, providing a more direct
route into the ventral aspect of the posterior fossa and clival region
Approaches to the anterior cranial base
(presigmoid retrolabyrinthine approach), while additional drilling of
the labyrinthine will facilitate opening of the internal acoustic canal
The anterior cranial fossa is formed by the frontal, ethmoid and sphen
(presigmoid translabyrinthine approach). Large lesions extending from
oid bones, and supports the frontal lobes of the cerebral hemispheres
the posterior to the middle fossa, typically petroclival meningiomas,


(see Figs 16.5, 28.2). There are two main transcranial approaches to this
can be removed using a combined presigmoid approach and temporal
region: anterior (or bifrontal transbasal) and anterolateral (or frontola
craniotomy with transection of the tentorium (presigmoid transtento
teral). The bifrontal transbasal approach consists of a bifrontal crani
rial approach) (Gross et al 2012).
otomy and provides direct access to the cribriform plate region and
The implementation of many of the skull base approaches detailed
planum sphenoidale bilaterally; the approach can be augmented with
here has evolved in recent decades, facilitated by the introduction of
orbital osteotomies that provide a more basal trajectory and hence
modern technology (surgical microscope, microinstrumentation, high
minimize brain retraction, and it can also include nasal bone and
speed drill) and the pioneer efforts of surgical innovators. The latest of
medial orbital wall osteotomies to enhance access the sinonasal cavity,
all innovations in skull base surgery has been the introduction of the
sphenoid sinus and clival region (FeizErfan et al 2008).
endoscopic endonasal approach, which uses the nostrils as natural cor
The frontolateral approach entails an ipsilateral craniotomy that
ridors to access the ventral aspect of the skull base. The transsphenoidal
provides access to the anterior skull base, anterior clinoid process, optic
route, described more than a century ago to access the sella turcica, can
canal and basal cisterns from a lateral to medial trajectory. It can be
now be greatly expanded thanks to the development of endoscopic
augmented with an orbital osteotomy to facilitate a more inferior to
visualization and specifically designed instrumentation. Accessing the
superior trajectory for lesions that expand in the vertical axis (Jane et al
skull base from the endonasal route is ideal for lesions located in the
1982, Delashaw et al 1993).
midline skull base because it facilitates a direct approach to the target
without any external incision, craniotomy or manipulation of the brain
Approaches to the middle cranial fossa


(Kassam et al 2005a, Kassam et al 2005b). The endoscopic endonasal
approach has become an excellent alternative choice for tumours such
The middle cranial fossa is formed by the sphenoid and temporal bones, as large pituitary adenomas (Paluzzi et al 2014, Koutourousiou et al
and supports the temporal lobes of the cerebral hemispheres (see Figs 2013a), craniopharyngiomas (Koutourousiou et al 2013b, Fernandez
16.5, 28.2). Lesions that are exclusively located in this fossa can be Miranda et al 2012), midline anterior and posterior skull base menin
accessed with a temporal craniotomy, which can be supplemented with giomas (Koutourousiou et al 2014, FernandezMiranda et al 2014a),
zygomatic osteotomies to improve the inferior to superior working cor chordomas and chondrosarcomas (FernandezMiranda et al 2014b,
ridor or to facilitate access to the infratemporal fossa by further mobi Koutourousiou et al 2012), given their favourable anatomical location.
lization of the temporalis muscle. Lesions, however, often occupy The main disadvantage of the endonasal approach in comparison to
anterior and middle cranial fossas, for which a frontotemporal or pte the open approaches is the more difficult skull base reconstruction,
rional craniotomy with optional orbitozygomatic osteotomies is typi currently solved largely with the use of pedicled vascularized flaps har
cally required. This craniotomy allows for an extradural middle fossa vested locally from the nasal septum.
approach, which consists of peeling away the meningeal layer of dura As a result, contemporary skull base surgery selectively uses and
of the middle fossa to expose the superior orbital fissure, lateral wall of occasionally combines transcranial and endonasal approaches to the
the cavernous sinus, V, V, Meckel’s cave and anterior petrous apex anterior, middle and posterior skull base for effective treatment. e43
2 3


Surgery of the Skull baSe
e44
4
NoItCeS
REFERENCES
Alaywan M, Sindou M 1990 Frontotemporal approach with orbito Kassam A, Snyderman CH, Mintz A et al 2005b Expanded endonasal
zygomatic removal. Surgical anatomy. Acta Neurochir (Wien) 104: approach: the rostrocaudal axis. Part II. Posterior clinoids to the foramen
79–83. magnum. Neurosurg Focus 19:E4.
Delashaw JB Jr, Jane JA, Kassell NF et al 1993 Supraorbital craniotomy by Kawase T, Toya S, Shiobara R et al 1985 Transpetrosal approach for aneur
fracture of the anterior orbital roof. Technical note. J Neurosurg 79: ysms of the lower basilar artery. J Neurosurg 63:857–61.
615–18. Koutourousiou M, Gardner PA, Tormenti MJ et al 2012 Endoscopic endo
FeizErfan I, Spetzler RF, Horn EM et al 2008 Proposed classification for the nasal approach for resection of skull base chordomas: outcomes and
transbasal approach and its modifications. Skull Base 18:29–47. learning curve. Neurosurgery 71:614–25.
FernandezMiranda JC, Gardner PA, Snyderman CH et al 2012 Craniopha Koutourousiou M, Gardner PA, FernandezMiranda JC et al 2013a Endo
ryngioma: a pathologic, clinical and surgical review. Head Neck 34: scopic endonasal surgery for giant pituitary adenomas: advantages and
1036–44. limitations. J Neurosurg 118:621–31.
FernandezMiranda JC, Gardner PA, Rastelli MM Jr et al 2014a Endoscopic Koutourousiou M, Gardner PA, FernandezMiranda JC et al 2013b Endo
endonasal transcavernous posterior clinoidectomy with interdural pitui scopic endonasal surgery for craniopharyngiomas: surgical outcome in
tary transposition. Technical note and clinical outcomes. J Neurosurg 64 patients. J Neurosurg 119:1194–207.


121:91–9. Koutourousiou M, FernandezMiranda JC, Stefko ST et al 2014 Endoscopic
FernandezMiranda JC, Gardner PA, Snyderman CH et al 2014b Clival chor endonasal surgery for suprasellar meningiomas: experience with 75
domas: a pathological, surgical and radiotherapeutic review. Head Neck patients. J Neurosurg 120:1326–39.
36:892–906. Paluzzi A, FernandezMiranda JC, Stefko ST et al 2014 Endoscopic endo
Gross BA, Tavanaiepour D, Du R et al 2012 Evolution of the posterior pet nasal approach for pituitary adenomas: a series of 555 patients. Pituitary
rosal approach. Neurosurg Focus 33:E7. 17:307–19.
Jane JA, Park TS, Pobereskin LH et al 1982 The supraorbital approach: tech Rhoton AI 2007 Cranial Anatomy and Surgical Approaches. Philadelphia:
nical note. Neurosurgery 11:537–42. Lippincott Williams & Wilkins.
Kassam A, Snyderman CH, Mintz A et al 2005a Expanded endonasal Wen HT, Rhoton AL Jr, Katsuta T et al 1997 Microsurgical anatomy of the
approach: the rostrocaudal axis. Part I. Crista galli to the sella turcica. transcondylar, supracondylar, and paracondylar extensions of the far
Neurosurg Focus 19:E3. lateral approach. J Neurosurg 87:555–85.


COMMENTARY
The role of three-dimensional imaging
4.2
in facial anatomical assessment
Vikram Sharma, Bruce Richard
‘What is a face, really? Its own photo? Its make-up? Or is it a face as take up to 20 seconds for image acquisition and is reliant on the subject
painted by such or such painter? … Doesn’t everyone look at himself in keeping absolutely still to prevent motion artefact, such as ridges, on
his own particular way? Deformations simply do not exist.’ the captured image (Bush and Antonyshyn 1996). Three-dimensional
photogrammetry is a software-driven approach utilizing multiple digital
Pablo Picasso
cameras set at different angles to acquire the facial image rapidly, in
(1881–1973)
little over a millisecond. Time-of-flight technology, which measures the
The face is central to human social interaction and it has been shown time taken for emitted light from an illumination unit to reach an
that symmetrical or ‘average’ faces are perceived as more attractive object and travel back to a detector, has been used by a range of scan-
(Baudouin and Tiberghien 2004). Even a minor visual difference can ners to make very precise measurements of distance. This technology
result in a reduced level of perceived attractiveness in general society uses either optical shutter technology or modulated light of various
and is associated with several negative factors concerning appearance, wavelengths to create a 3D image of the actual face and head (Zhang
symmetry and facial expression. This, in turn, adversely affects the and Lu 2013). It allows human faces to be recognized and tracked in
quality of life of a person and has been shown to trouble patients with real time in a manner that is both rapid and efficient from a computa-
cleft lip and palate – the most common craniofacial deformity, which tional standpoint. Furthermore, it is not affected by differences in facial
is present in 1 in 700 live births (Mossey et al 2009). This can cause orientation, illumination or features that might obscure part of the face
emotional distress in childhood and adolescence due to teasing from (Meers and Ward 2009). The nasal tip is the optimal facial landmark
peers, and subsequent unhappiness with facial appearance into adult- to use, as it is easily detected by an observer, has a central position on


hood, despite optimal surgical correction (Marcusson 2001). the face and is not usually obscured by hair or spectacles (Gorodnichy
Embryologically, all tissues of the head and face of vertebrates are 2002). Furthermore, it has certain geometric and illumination charac-
derived from the three primary germ layers (endoderm, mesoderm, teristics from which spherical intersection profiles are utilized to obtain
ectoderm) and a fourth layer, the neural crest. This was originally a ‘faceprint’ that is then normalized. However, there are currently no
described by Wilhelm His in 1868 as the intermediate cord or ‘cord in clinical validation studies for facial assessment using time-of-flight 3D
between’ the neural plate and non-neural ectoderm, in studies on chick cameras.
embryos (His 1868). Through migration and proliferation of neural Gross anatomical landmarks on the face are captured by a series of
crest cells in the branchial arches at the fourth week of gestation, five relatively simple measurements. Delineation of finer features that will
facial primordia develop around the primitive mouth or stomatodeum. allow a detailed surface-based analysis of facial shape, however, requires
They include: a single frontonasal prominence (forming forehead, a significantly larger number of densely arranged surface points corres-
middle of the nose, philtrum and primary palate) and paired mandibu- ponding to quasi-landmarks. Tens of thousands of these points can be
lar and maxillary prominences (lower jaw, middle and lower face, derived from as few as 22 facial landmarks. A technique known as thin-
lateral border of lips and secondary palate) (Baynam et al 2013). The plate spline warping will then pull these points on the surface of the
proportions and position of various facial features continue to develop face together, similar to a thin sheet of rubber, into a precise alignment.
slowly from week eight until birth, with the rapidly enlarging brain The number of landmarks chosen is a balance, as too few will cause the
causing the ears to rise, the eyes to move medially and the forehead to face scan to be registered poorly and too many will result in significant
become more apparent. noise that causes the placement of soft-tissue landmarks on a virtual


While human facial anatomy can be thought of as largely similar, image to be inaccurate (Hammond et al 2004).
with features such as eyes, nose and mouth approximately in the same A further advantage of digital anthropometry is that it obviates the
location, there are enough minor differences in proportions, size and need for a general anaesthetic in a young, uncooperative patient and/
position both between and within different ethnicities to make us all or exposure to a high-dose of ionizing radiation as would be the case
unique individuals. When considering more local features such as inner if using either computed tomography or computed axial tomography
and outer canthi, columella or philtrum, there can be considerable dif- (CT/CAT scanning). CAT is not the best modality for evaluation of soft
ferences in addition to the effects of congenital malformations or tissue structures, and current protocols tend to be focused on the brain,
acquired deformities due to trauma and surgical repair. The human face with facial imaging omitted or distorted by an endotracheal tube (Lit-
is a complex three-dimensional (3D) structure and capturing an image tlefield et al 2004). Examples of a widely used, commercially available,
in its entirety with true-to-life precision is likely to be challenging 3D surface imaging modality and system based on active stereo photo-
for both human and machine. A systematic review of methods of grammetry are shown in Figure 4.2.1 and Video 4.2.1.
facial aesthetic assessment in a specific patient population and a rating Three-dimensional facial imaging has significant potential for accu-
system for outcome comparison have been described previously rately capturing the human face in health and disease. Current research
(Sharma et al 2012). aims to validate protocols that hopefully will translate into routine
Traditionally, direct facial measurements have been taken using clinical practice. The FaceBase Consortium from the National Institute
manual anthropometry utilizing rulers, tape measures and callipers, as of Dental and Craniofacial Research (National Institutes of Health,
pioneered by Leslie Farkas, the father of modern craniofacial anthro- USA) is utilizing 3D active stereo photogrammetry in concert with high-
pometry (Farkas 1994). Although low-cost and straightforward, this throughput DNA sequencing of thousands of individuals to map accu-


method requires a high degree of cooperation from the subject and is rately how normal facial features are influenced by genetic determinants
very labour-intensive if used to assess hundreds of individuals to obtain (Hochheiser et al 2011). This will be further aided by its Ontology of
representative normative data. Digital photography, by contrast, pro- Craniofacial Development and Malformation project, which aims to
vides a rapid and permanent image that can be rapidly processed and gather wide-ranging, specifically annotated data from multiple sources,
archived on to computer databases. Drawbacks of using a two- ranging from the level of genes to gross anatomical structures and clini-
dimensional (2D) modality to derive accurate facial measurements cal images, to unravel causal mechanisms of craniofacial deformity
include differential positioning of subjects despite a standardization (Brinkley et al 2013).
protocol and perspective projection distortion, where a 3D object is Genome-wide association studies (GWAS) describe case-control
unavoidably misrepresented by an attempted projection on to a 2D studies where single nucleotide polymorphisms (SNPs), the most
plane. common form of genetic variation in the genome, are compared
Capturing a face in three dimensions is mainly achieved by laser between affected and non-affected individuals for a particular disease.
scanning or stereo photogrammetric devices that can capture many Two independent GWAS projects have implicated the gene PAX3 (paired
thousands of points in an instant. The former method, however, can box 3) in craniofacial development and facial morphology (particularly e45


The role of Three-dimensional imaging in facial anaTomical assessmenT
e46
4
noiTces
Later, in a second and importantly independent GWAS, Liu et al (2012)
identified five genetic loci (all at p <5 × 10−8 significance threshold) that
are associated with face morphology, but with a small effect size. Again,
SNPs associated with PAX3 were found to influence the position of the
nasion. A candidate gene found at a second locus, TP63 (transformation
related protein 63), is associated with orofacial clefting both in humans
with heterozygous mutations and in null mice. Phenotyping in this
study was performed using 3D magnetic resonance imaging (MRI) of
nine facial landmarks of the upper face and midface but missed features
of the lower face – a drawback easily obviated by the use of 3D stereo
photogrammetry.
A GWAS of patients with cleft lip, with or without cleft palate,
undertaken in 825 European and 1038 Asian ancestry case-parent
trios, identified SNPs associated with two novel genes (MAFB – v-Maf
avian musculoaponeurotic fibrosarcoma oncogene homolog B1 – and
ABCA4 – ATP-binding cassette, sub-family A (ABC1), member 4), a
known gene (IRF6 – interferon regulatory factor 6, mutations of which
cause Van der Woude’s syndrome) and a known region (8q24, associ-
ated with non-syndromic cleft lip/palate) (Beaty et al 2010). Expres-
sion studies in mice using in situ hybridization of MAFB showed strong
staining in the epithelium around palatal shelves and medial fusing
palatal edges, as well as the oral epithelium, implicating a role for this
Fig. 4.2.1 An example of a commercially available three-dimensional gene in normal lip and palate development (see Ch. 36).
active stereo photogrammetry device (3dMD) in use at a national imaging Characterizing a normal individual face as accurately as possible
research project (‘MeIn3D’) at the London Science Museum, UK (2012). may facilitate genotype–phenotype correlation of diseases with specific


(Courtesy of Ms Kelly Duncan (3dMD).) facial features. It should also highlight more discrete facial characteris-
tics that might be present as part of a craniofacial syndrome, but not
immediately apparent to all but the most experienced dysmorphologist.
the positioning of the nasion) in stratified European populations. This Coordinated research efforts that combine molecular biology with
gene encodes a transcription factor expressed by neural crest cells, advanced facial imaging will no doubt improve the accuracy of clinical
important in vertebrate facial patterning. Mutations of PAX3 are associ- diagnosis and lead to stratified medical practice that is better tailored
ated with Waardenburg syndrome, typified by telecanthus, a broad and to patient care.
high nasal root, deafness and pigmentation abnormalities of the hair,
Acknowledgement
skin and eyes (Waardenburg 1951). Paternoster et al (2012) used 3D
laser scanning to identify 22 landmarks in over 3000 individuals geno-
typed for nearly 300,000 SNPs and found an association between The authors wish to express their appreciation to Ms Kelly Duncan
rs7559271 (located in an intronic region of PAX3) and nasion position. (3dMD) for the kind provision of images and video for this article.
REFERENCES
Baudouin JY, Tiberghien G 2004 Symmetry, averageness, and feature size in Littlefield TR, Kelly KM, Cherney JC et al 2004 Development of a new three-
the facial attractiveness of women. Acta Psychol 117:313–32. dimensional cranial imaging system. J Craniofac Surg 15:175–81.
Baynam G, Walters M, Claes P et al 2013 The facial evolution: looking Liu F, van der Lijn F, Schurmann C et al 2012 A genome-wide association
backward and moving forward. Hum Mutat 34:14–22. study identifies five loci influencing facial morphology in Europeans.
Beaty TH, Murray JC, Marazita ML et al 2010 A genome-wide association PLoS Genet 8:e1002932.
study of cleft lip with and without cleft palate identifies risk variants Marcusson A 2001 Adult patients with treated complete cleft lip and palate:


near MAFB and ABCA4. Nat Genet 42:525–9. methodological and clinical studies. Swed Dent J 145(Suppl):1–57.
Brinkley JF, Mejino JL, Detwiler LT et al 2013 Towards understanding cranio- Meers S, Ward K 2009 Face recognition using a time-of-flight camera. Pro-
facial abnormalities: the ontology of craniofacial development and mal- ceedings of the 2009 Sixth International Conference on Computer
formation. AMIA Summits Transl Sci Proc 2013:20. Graphics, Imaging and Visualisation (CGIV ′09); pp. 377–83.
Bush K, Antonyshyn O 1996 Three-dimensional facial anthropometry using Mossey PA, Little J, Munger RG et al 2009 Cleft lip and palate. Lancet
a laser surface scanner: validation of the technique. Plast Reconstr Surg 374:1773–85.
98:226–35.
Paternoster L, Zhurov AI, Toma AM et al 2012 Genome-wide association
Farkas LG 1994 Anthropometry of the head and face. New York: Raven. study of three-dimensional facial morphology identifies a variant in
Gorodnichy DO 2002 On importance of nose for face tracking. Proceedings PAX3 associated with nasion position. Am J Hum Genet 90:478–85.
of Fifth IEEE International Conference on Automatic Face and Gesture Sharma VP, Bella H, Cadier MM et al 2012 Outcomes in facial aesthetics in
Recognition, 2002 May 20–21; Washington, DC: Institute of Electrical cleft lip and palate surgery: a systematic review. J Plast Reconstr Aesthet
Engineers; pp. 188–93. Surg 65:1233–45.
Hammond P, Hutton TJ, Allanson JE et al 2004 3D analysis of facial mor- Waardenburg PJ 1951 A new syndrome combining developmental anoma-
phology. Am J Med Genet A 126A:339–48. lies of the eyelids, eyebrows and nose root with pigmentary defects of
His WS 1868 Untersuchungen über die erste Anlage des Wirbeltier-leibes. the iris and head hair and with congenital deafness. Am Hum Genet


Die erste Entwickelung des Hühnchens im Ei. Leipzig: FCW Vogel. 3:195–253.
Hochheiser H, Aronow BJ, Artinger K et al 2011 The FaceBase Consortium: Zhang D, Lu G 2013 The Principle of 3D Camera Imaging. 3D Biometrics.
a comprehensive program to facilitate craniofacial research. Dev Biol New York: Springer; pp. 233–56.
355:175–82.


COMMENTARY
4.3
Anatomy of facial ageing
Bryan C Mendelson, Chin-Ho Wong
Overview which they are programmed to move, and have minimal attachment to
the underlying skeleton. A discontinuous glide plane layer beneath the
muscle layer consists of spaces that allow movement of the overlying
The human face undergoes dramatic changes of appearance with ageing;
soft tissues.
these changes are so consistent and predictable that they reveal a per-
The soft tissues of the face are stabilized in position by an extensive
son’s age. In youth, the surface of the face is a continuous smooth
fibrous support system that is unique to the facial structure (Furnas
structure on which only the major features – the eyes, nose and mouth
1989, Stuzin et al 1992). The system takes its fixation from attachment
– are identified. However, the surface changes with the ageing process
to the underlying skeleton and provides strong direct support to the
and progressively reveals the internal structure. Ageing is not uniform
dermis via its layered arrangement. Overlying the cavities, the support
across the face because the various functional regions age differently.
system is necessarily modified by the absence of bone for ligamentous
Facial ageing takes place essentially around the eyes and mouth and
fixation, which means that support over the orbital and oral cavities is
over the neck.
indirect. The support of the specialized, very mobile, soft tissues that
Most ageing is seen on the anterior face, the face proper, where the
form the eyelids over the orbital cavity and the part of the cheek that
specific facial features are located. The lateral aspect of the face is quite
overlies the extensive vestibule of the oral cavity, together with the soft
distinct from the anterior face, both functionally and structurally. The
tissue apertures forming the lid margins and the lips, is therefore struc-
soft tissues on the lateral face change less because they are not actively
turally compromised. Bony rims provide the skeletal base for this indi-
involved with the underlying structures (temporalis, masseter, arch of
rect ligamentous attachment around the bony cavities. Focused areas of
zygoma and parotid gland), whose only function is mastication.
greater support, e.g. the canthal tendons, are found within the cavities.
Ageing happens at all tissue levels; whether these changes develop


Further adaptations of the fibrous support system are necessary over the
primarily at one or more levels and lead to secondary changes at the
oral cavity because here the bony rim is not fixed and continuous, as it
other levels is not known, but their appearance is concurrent.
is in the orbital rim, but enlarges with jaw movement.
The combination of soft tissue movement over the orbital and oral
Soft tissue organization of the face cavities, along with the necessary reduction of ligamentous support to
allow this movement, is the basis for the ageing of the soft tissue around
Ageing of the face, and the extent of the changes involved, are conse- the eye and around the mouth.
quences of its unique functions. These require mobility of the soft
tissues that is not found elsewhere in the body and that necessitates Overview of facial ageing
major structural adaptations. In most regions of the face, there are
conflicting structural requirements for mobility over support (fixation). The general pattern with ageing is a progressive loss of facial volume
Ultimately, the requirements for movement determine the need for with increasing laxity and possibly expansion of the outer layers with
areas of reduced fixation that contribute so much to the changes that descent. The smooth, taut surface of a full and uniformly rounded
we recognize as ageing. youthful face deteriorates with ageing to form a series of individual
The facial skeleton provides a foundation to which the overlying soft segments that are separated by surface grooves located where internal
tissues are variably attached (Furnas 1989, Stuzin et al 1992). Having ligaments attach to the dermis, and that progress to form skin creases
a strong facial skeleton is the single most important determinant in or wrinkles as the dermis weakens (Mendelson and Jacobson 2008).
‘ageing well’, meaning at a slower rate than average. The multiple bones The multiple structures of the face are interconnected at several
of the facial skeleton have diverse embryonic origins; the most signifi- levels. Changes in one structure will have an impact on the others and,
cant in ageing are the odontogenic bones (maxilla and mandible). The in more advanced ageing, simultaneous changes in more than one
skeleton protects the receptor organs of the central nervous system, i.e. component will produce a cumulative effect. The extent to which these


visual, olfactory and auditory receptors, in a series of cavities that are changes are attributable primarily to ageing, e.g. whether laxity arises
‘open’ to the exterior, together with the expansile, mobile, oral cavity. secondary to volume loss or from intrinsic weakening of ligament
With the exception of the ear, all the cavities are located on the front strength or is a combination of both effects, is not clear. The only certain
of the face and their presence contributes to ageing of the mid-cheek. primary change is a loss of anterior volume of the maxilla that is associ-
Musculoskeletal movement in the face is initiated only from the ated with the eruption of the secondary dentition.
temporomandibular joint; the two major skeletal masticatory muscles
(temporalis and masseter) are located beneath the deep fascia of the Details of tissue layers
lateral face. The soft tissues overlying the lower third of the face are
significantly impacted by this skeletal movement, as well as by the
Tissue planes, sub-SMAS spaces
extensive movement of the subjacent neck.
and facial ageing
The facial soft tissues have considerable capacity for movement.
Active movement, a unique feature of facial anatomy, arises on the The facial soft tissues are organized in concentric tissue layers (Fig.
anterior face, primarily in relation to the orbital and oral cavities, as a 4.3.1). The superficial muscles are in the middle layer (layer three),
result of the contraction of the sphincter muscles embedded in the soft although muscle is not present in all areas of the face. The layer is
tissues overlying the cavities. Movement around the orbit is modified fibroaponeurotic where muscle is not present; hence the name, super-
by the forehead and glabellar musculature and by the orbital part of ficial musculo-aponeurotic system (SMAS) (Mitz and Peyronie 1976),
orbicularis oculi. The lip elevator and depressor muscles add to the lip (see Ch. 30). Functionally, this layer is related to the skin, via the con-
movement around the oral sphincter. Movement on the lateral face nections of the retinacula cutis in the subcutaneous layer, rather than
is passive only, secondary to major tissue displacements extending to the deeper structures. In an arrangement that resembles that of the


from the anterior face, or to movement of the underlying mandible or structure of the scalp, the outer three layers of the face form a composite
neck. anatomical unit, whose quality of adherence varies according to the
The concentric layered structure of the face allows movement to take character of the SMAS in each area. The SMAS is muscular where move-
place. The driver of movement is the separate layer of superficial ment happens (frontalis, orbital part of orbicularis oculi and platysma)
muscles, the so-called ‘muscles of facial expression’ (Ch. 30). These and is also mobile, with a looser deep attachment as well as less tight
muscles are intimately attached to the overlying soft tissues and skin, subcutaneous connections; laxity develops in these areas with ageing e47


AnAtomy of fAciAl Ageing
e48
4
noitceS
PAF
a
b
c Fig. 4.3.2 Ligamentous arrangement of the lateral face. The structures
of the lateral face reflect its masticatory function. From above, these
structures are: temporalis fascia; arch of zygoma; masseter (largely
d overlain by the parotid and masseteric fasciae). The body of the zygoma
separates the orbital and oral cavities. The prezygomatic space overlies
the body of the zygoma, between the orbicularis retaining ligament
around the orbit above and the zygomatic ligaments above the oral
cavity. The platysma auricular fascia (PAF) on the surface of the parotid is
e a diffuse area of ligamentous fusion of the parotid capsule with the
overlying superficial musculo-aponeurotic system (SMAS). The vertical line
of ligaments in relation to the anterior edge of masseter provides support
for the SMAS over the oral cavity. A series of premasseteric spaces
Fig. 4.3.1 The three-dimensional arrangement of the ligaments of the overlie masseter, in the interval between the concave anterior border of
facial soft tissues. The ligaments take origin from the deep fascia and the parotid gland (including its accessory lobe) and the line of masseteric
form septa-like boundaries in the temple. The main ligaments around the ligaments. These spaces allow gliding movement of the composite soft
oral cavity extend through the superficial musculo-aponeurotic system tissues associated with the oral cavity and opening the jaw.
(SMAS) and subcutaneous layers to the dermis. Key: a, zygomatic
ligament; b, uppermost masseteric ligament; c, upper key masseteric
ligament; d, lower key masseteric ligament; e, mandibular ligament.
The most significant change is retrusion of the maxilla, which con-
tributes directly to the loss of mid-cheek support and affects the inferior
(Rohrich and Pessa 2007). In contrast, the fibrous aponeurotic SMAS orbital rim, piriform and oral cavities, leading to ‘sagging’ of the soft


lacks intrinsic mobility and, as seen over the lateral face, is fixed directly tissues of the medial suborbital region (Fig. 4.3.4) (Pessa et al 1998,
to the underlying deep fascia, the parotid fascia, where it maintains a Shaw and Kahn 2007, Mendelson et al 2007).
tight skin attachment (Furnas 1994). The dimensions of the orbital aperture increase slightly but are sig-
The fourth layer, the sub-SMAS plane, is effectively a glide plane nificant in periorbital ageing. Recession of the inferolateral rim (by
that allows movement of the composite flap independent of the deep more than 10%) causes the greatest alteration of orbital shape. The
fascia. This involves a discontinuous series of sub-SMAS spaces that changes exhibit sexual dimorphism in that they are generally seen at a
are located above and lateral to the mobile oral cavity (Fig. 4.3.2) younger age in women (by middle age) compared to men. Thus, a small
(Mendelson 2007). increase of transverse orbital width and aperture area happens earlier
The SMAS of the mid-cheek, i.e. the anterior face between the lower in women, and superomedial recession occurs later and to a greater
eye lid and lips, includes the orbital part of orbicularis oculi. It covers extent in men (Kahn and Shaw 2008).
the large area overlying the vestibule of the oral cavity and its support Soft tissue laxity of the lower face accompanies the reduction in size
is limited largely to its superolateral corner, where it is provided by the of the mandible. By middle age, there is a considerable reduction of the
zygomatic ligament. This robust structure does not tend to weaken; mandibular angle with shortening of the length of the mandibular body
however, distension of the cheek SMAS tends to develop. and its height; shortening of the height of the ramus occurs later (Pessa
The lower premasseteric space is the largest of the sub-SMAS spaces et al 2008, Shaw et al 2010).
lateral to the oral cavity. It overlies the masseteric fascia above the man-
Retaining ligaments and ageing
dibular rim, and prevents soft tissue drag from movement of the mouth


that would restrict opening of the jaw. With ageing, weakness of the A discontinuous vertical line of retaining ligaments separates the lateral
lower masseteric ligaments allows distension of its anterior and inferior face from the anterior face (see Fig. 4.3.2). The skeletal origin of the
boundaries and the roof formed by platysma, resulting in the formation ligaments continues from the anterior end of the superior temporal
of the jowl (Fig. 4.3.3) (Mendelson et al 2008). The buccal fat pad, line, down the lateral orbital rim to the body of the zygoma, and down
when compact, adds to youthfully compact cheeks (see Fig. 30.18A). the anterior border of masseter to the mandibular ligament. There is
However, when there is weakness of the lower masseteric ligaments no evidence to suggest that weakening of the main ligaments, where
(normally holding platysma in close relation to the masseteric fascia), movement is least (specifically, the stronger zygomatic ligaments on the
the buccal fat pad becomes more mobile, and it may descend into a zygoma), contributes to facial laxity, although the lower premasseteric
more anterior location towards the corner of the mouth, adding to ligaments do weaken in their effect.
fullness of the labiomandibular fold. The attachment of ligaments to the dermis is responsible for the
cutaneous grooves that appear with ageing, e.g. the palpebromalar,
The facial skeleton and its ageing
nasojugal, mid-cheek and nasolabial grooves, whereas the surface
The facial skeleton is not only the foundation of a person’s individual bulges, e.g. the malar mound, nasolabial fold and jowl, overlie the
appearance but also a key determinant of how that person ages, because spaces between the ligaments (Mendelson et al 2002). The part of the
the projection of the skeleton provides support for the overlying soft orbicularis retaining ligament that crosses the central inferior orbital
tissues. It is now known that the facial skeleton is not static and changes rim is distensible and allows the orbital fat to bulge as ‘fat bags’ (Fig.


significantly with age. Accordingly, people who lack strong skeletal 4.3.5), whereas shrinkage of the maxilla at the medial end of the orbital
projection are prone to premature ageing because they have less ‘in rim pulls the ligaments (tear trough ligament). Below, as the medial
reserve’ when ageing starts with the loss of skeletal volume and maxillary ligament is pulled back into the face, the depth of the nasola-
projection. bial groove is increased.


Anatomy of facial ageing
e49
3.4
yRAtnemmoc
A B
Fig. 4.3.3 The origin of the jowl with ageing and the changing relations of platysma and masseter. A, In youth, platysma, which forms the roof of the
lower premasseteric space, is in close and tight relation to the anterior border of masseter via the vertical line of ligaments. B, The jowl develops as a
result of the developing laxity and distension of the septa-like lower masseteric ligaments. This allows enlargement of the lower premasseteric space,
specifically of its anterior and lower boundaries and the adjacent roof. This ligamentous weakness allows the inferior extent of the buccal fat pad to
prolapse, which contributes fullness to the labiomandibular fold above the jowl.
Fig. 4.3.4 Changes of the facial skeleton with
ageing. The most significant amount of bony
change is the mid-cheek skeleton. Shrinkage of
the anterior projection of the maxilla predominates,
along with a reduction of the bony rim of the
piriform aperture. The inferior orbital rim, where it
is formed by the zygoma, becomes more rounded,
whereas the medial rim, where it is formed by the
maxilla, loses its thickness. The anterior surface of
the mandible becomes more hollowed and prejowl
hollowing appears.
with advanced ageing due to a combination of their descent from fixed
Subcutaneous layer and ageing
structures – in particular, the bony rims (superior and inferior orbital
The fat and fibrous components in the subcutaneous tissue are not and mandibular border), as well as changes in the volume distribution
uniform but arranged in discrete compartments that are delimited by within the compartments, with increasing inferior fullness (Gierloff
septal boundaries related to the dermal extensions of the retaining liga- et al 2012). These changes have been attributed to a number of causes,
ments (Rohrich and Pessa 2008). In youth, the boundaries between including selective atrophy or hypertrophy and attenuation of the
compartments are not discernible on the surface: with ageing, a series retaining ligaments that allow fat redistribution within compartments.


of contour changes occur in which concavities separate the convexities It is now believed that fat descent with ageing is less than it appears;
that reflect these compartments. Specific names have been given to distinct compartmentalization by the retaining ligaments holds the fat
certain areas of the subcutaneous layer at sites where the subcutaneous in its relative positions, and it is likely that the reduction of internal
fat becomes more prominent, e.g. the malar fat pad and nasolabial fat. volumes deep to the subcutaneous fat accounts for the major part of
The changes of the subcutaneous compartments become most apparent the appearance of descent, especially of the mid-cheek (Lambros 2007).


AnAtomy of fAciAl Ageing
e50
4
noitceS
A B
TT
LML
MML
LML
MML
Nasolabial
crease
C D
Fig. 4.3.5 Linking of ageing changes through the tissue layers. A, Youthful. B, Aged. C–D, Sections taken through the mid-cheek. The changes in the
bony orbital rim (inferolateral resorption and blunting of the sharply defined rim) are associated with changes of the attached septum orbitale, which
undergoes attenuation and distension. The bulging retroseptal orbital fat associated with this weakening extends over the rim until constrained by the
stronger orbicularis retaining ligament. The orbicularis retaining ligament is attached several millimetres outside the rim. The medial third, named the tear
trough (TT) ligament, is drawn posteriorly by the reduction of anterior maxillary volume. The bony change, expressed through the ligament, accentuates
the depth of the nasojugal groove. Maxillary resorption around the piriform aperture accentuates the depth of the nasolabial groove and crease as it
causes the medial maxillary ligament (MML) to become similarly indrawn. In the same way, the lateral maxillary ligament (LML), between zygomaticus
minor and levator labii superioris, draws the tissues deeper. By contrast the major ligaments that provide support for the soft tissues over the oral cavity
(zygomatic, upper masseteric and mandibular) are essentially unchanged with ageing. The ageing weakness of the cheek soft tissues occurs within the
SMAS and the thicker subcutaneous layer.
The reduction of skeletal support places strain on the ligamentous
Sequence of appearance of facial ageing
boundaries, such as the orbicularis retaining ligament and the lateral
canthal tendon, and this leads to the onset of weakening and eventual
While ageing is traditionally associated with the presence of wrinkles, lengthening, and bulging of the deeper structures they previously
in reality the earliest onset of ageing probably results from a reduction supported.
of skeletal volume. Facial skeletal changes are inevitable and appear Dynamic expression lines develop with muscle contraction: while
early because they are a consequence of the reshaping of the maxilla not present in youth, they increase with the reduction of ligamentous


and mandible that follows the eruption of the secondary dentition. tissue resistance. With age, muscle contraction produces an increased
While the changes of the deeper skeleton are not immediately appar- amplitude of tissue displacement, e.g. movement of the eyebrows and
ent, they contribute to a cascade of secondary changes due to the cheeks when they are elevated from a sagged position results in the
interlinking of the tissue layers. Accordingly, the deep fat, preperiosteal frontalis lines of the forehead and periorbital crow’s feet lines, respec-
and buccal, also has less projection; with the reduction of tissue tone, tively. As the quality of the dermis deteriorates, the lines deepen, espe-
there is an effect on the ligaments, producing early laxity and sag. cially perioral wrinkles.


Anatomy of facial ageing
e51
3.4
yRAtnemmoc
Small reductions of facial volume, whether of bone or fat (deeper leaning forwards; its visibility is decreased when recumbent. Changes
supraperiosteal fat, as well as subcutaneous fat), contribute to loss of to the quality of the subcutaneous layer appear with more advanced
tone in the composite outer layers and laxity of the finer ligaments. ageing. The changes described above are endogenous. Dermal changes
Tissue laxity that is initially latent is revealed under the influence of reflect the long-term effect of environmental damage more and are
gravity. It becomes apparent with the head up and is exacerbated when exaggerated by tissue laxity.
REFERENCES
Furnas DW 1989 The retaining ligaments of the cheek. Plast Reconstr Surg Mitz V, Peyronie M 1976 The superficial musculo-aponeurotic system
83:11–6. (SMAS) in the parotid and cheek area. Plast Reconstr Surg 58:80–8.
Furnas D 1994 The superficial musculoaponeurotic plane and the retaining Pessa JE, Zadoo VP, Mutimer KL et al 1998 Relative maxillary retrusion as a
ligaments of the face. In: Psillakis JM (ed) Deep Face-lifting Techniques. natural consequence of aging: combining skeletal and soft-tissue
New York: Thieme Medical Publishers. changes into an integrated model of midfacial aging. Plast Reconstr Surg
Gierloff M, Stohring C, Buder T et al 2012 Aging changes of the midfacial 102:205–12.
fat compartments. A computed tomographic study. Plast Reconstr Surg Pessa JE, Slice DE, Hanz KR et al 2008 Aging and the shape of the mandible.
129:263–73. Plast Reconstr Surg 121:196–200.
Kahn DM, Shaw RB Jr 2008 Aging of the bony orbit: a three-dimensional Rohrich RJ, Pessa JE 2007 The fat compartments of the face: anatomy and
computed tomographic study. Aesthet Surg J 28:258–64. clinical implications for cosmetic surgery. Plast Reconstr Surg 119:
Lambros V 2007 Observations on periorbital and midface aging. Plast 2219–27.


Reconstr Surg 120:1367–76. Rohrich RJ, Pessa JE 2008 The retaining system of the face: histologic evalu-
Mendelson BC 2007 Advances in the understanding of the surgical anatomy ation of the septal boundaries of the subcutaneous fat compartments.
of the face. In: Eisenmann-Klein M, Neuhann-Lorenz C (eds) Innova- Plast Reconstr Surg 121:1804–9.
tions in Plastic and Aesthetic Surgery. New York: Springer Verlag; Ch. Shaw RB Jr, Kahn DM 2007 Aging of the midface bony elements: a three-
18, pp. 141–5. dimensional computed tomographic study. Plast Reconstr Surg 119:
Mendelson BC, Jacobson SR 2008 Surgical anatomy of the midcheek; facial 675–81.
layers, spaces, and midcheek segments. Clin Plast Surg 35:395–404. Shaw RB Jr, Katzel EB, Kolz PF et al 2010 Aging of the mandible and its
Mendelson BC, Muzaffar AR, Adams WP Jr 2002 Surgical anatomy of the aesthetic implications. Plast Reconstr Surg 125:332–42.
midcheek and malar mounds. Plast Reconstr Surg 110:885–96; discus- Stuzin JM, Baker TJ, Gordon HL 1992 The relationship of the superficial and
sion 897–911. deep facial fascias: relevance to rhytidectomy and aging. Plast Reconstr
Mendelson BC, Hartley W, Scott M et al 2007 Age-related changes of the Surg 89:441–9.
orbit and midcheek and the implications for facial rejuvenation. Aes-
thetic Plast Surg 31:419–23.
Mendelson BC, Freeman ME, Wu W et al 2008 Surgical anatomy of the lower
face: the premasseter space, the jowl, and the labiomandibular fold.
Aesthetic Plast Surg 32:185–95.


CHAPTER
43
Back
Most clinical disorders of the back present as low back pain with or Veins drain the skin of the back of the neck into tributaries of the
without associated lower limb pain, weakness or numbness, and so, occipital and deep cervical veins. The skin of the back of the trunk
historically, most attention has been paid to the anatomy of the lower drains into the azygos system, via tributaries of the posterior intercostal
(lumbosacral) back. In this Section, the term ‘back’ will include the and lumbar veins.
whole of the posterior aspect of the trunk and of the neck. The whole Lymph from the skin of the back of the neck drains into occipital,
of this region has great clinical importance but its anatomy has often lateral deep cervical and axillary nodes (Fig. 43.5). From the back of
been neglected. Recent understanding of the detailed topography of the the trunk, drainage is to the posterior (subscapular) axillary nodes and
bony and soft tissue elements of the lower back owes much to the work to the lateral superficial inguinal nodes.
of Bogduk (2005).
The soft tissues of the back of the trunk and neck include the skin
FASCIAL LAYERS
and subcutaneous fat, the underlying fascial layers and the musculature.
The deep, ‘true’ or epaxial muscles lie within compartments in their
own fascial ‘skeleton’. The bony framework to which the muscles and The main fascial layers in the axial and paraxial regions of the trunk
fasciae attach includes elements of the axial skeleton, i.e. the vertebral and neck are the thoracolumbar fascia, the deep cervical fascia and the
column and occiput, elements of the pectoral and pelvic girdles, and prevertebral, endothoracic, retroperitoneal and posterior parts of the
the ribs. The occiput is described below, the scapula on page 801, the pelvic fasciae (the latter four layers collectively form the continuous
ribs on page 934 and the pelvis on page 1339. prevertebral plane). Other important structures with fascial compo-
nents are the ligamentum nuchae and the aponeurosis of erector spinae
(see below).
SKIN


The skin of the back of the trunk is thick and highly protective, but has
low discriminatory sensation. The superficial fascia is thick and fatty in
most areas of the back. Its attachment to the deeper fascial layers is
strong in the midline, especially in the neck, but becomes weaker more
laterally. The skin of the back of the neck is thicker than that of the
front of the neck, but thinner than that of the back of the trunk. The
quantity, texture and distribution of hair vary with sex, race and
the individual, though well-defined hair tracts have been delineated
(Fig. 43.1).
Lines of skin tension run horizontally in the cervical and lumbosac-
ral regions but form segments of two adjacent circles in the thoracic
region (Fig. 43.2).
CUTANEOUS INNERVATION AND DERMATOMES
The skin of the back of the neck and trunk is innervated by the dorsal
(posterior primary) rami of the spinal nerves (see Fig. 45.10 and pp.
768–769, where dorsal rami are covered in detail). In the cervical and
upper thoracic regions (down to T6) skin is supplied by the medial
branches of these rami, while in the lower thoracic, lumbar and sacral
regions it is supplied by the lateral branches. The total area supplied by
these dorsal rami is shown in Figure 45.12. The spinal nerves involved
include C2–C5, T2–L3, S2–S4 and Co1. The pattern of their der-
matomes is shown in Figure 43.3. There is about half a segment of
overlap between these cutaneous ‘strips’; the strips supplied by the
dorsal rami do not correspond exactly to those served by ventral rami,
and differ slightly in both width and position.
CUTANEOUS VASCULAR SUPPLY
AND LYMPHATIC DRAINAGE
The skin of the back of the trunk receives its arterial blood supply
mainly from musculocutaneous branches of posterior intercostal,
lumbar and lateral sacral arteries (Fig. 43.4), which all accompany the
cutaneous branches of their respective dorsal rami. In addition, there
is a supply from the dominant vascular pedicles of the superficial
(extrinsic) back muscles. The skin over the scapula is supplied by


branches of the suprascapular, dorsal scapular and subscapular arteries.
The skin of the back of the neck is supplied mainly from the occipital
and deep cervical arteries. The superficial cervical or transverse cervical Fig .43 .1 Hair tracts on the dorsal surface of the body . (Redrawn with
artery supplies the skin of the lower part of the back of the neck permission from Wood Jones F (ed) 1949 Buchanan’s Manual of
710 (Cormack and Lamberty 1994). Anatomy, 8th edn . London: Baillière Tindall and Cox .)


Bones
711
34
RETPAHC
Fig .43 .2 Lines of skin
tension on the dorsum
of the trunk and head . C2
(With permission from C3
Kraissl CL, Plast C4
C2 C5
Reconstruct Surg 8: C6
1–28, 1951, Lippincott C3 C7
T1
Williams and Wilkins .)
C4 T2
T2
T4 T3
T6 T5
T2
T8 T7
C5 L1
T10 T9 L2
T12 T11 T1 C7 L L3 4
L5
S1
L1
S2
S3
L2 S4
S3 C6 S5
C8
S4
L3
S2
L5
L4
S1
L5
THORACOLUMBAR FASCIA Fig .43 .3 Dermatomes on the dorsal surface of the body . The small
diagram shows the regular arrangement of dermatomes in the upper and
The thoracolumbar (lumbodorsal) fascia covers the deep muscles of the lower limbs of the embryo . Maps of dermatome distribution are useful in
back and the trunk. Above, it passes anterior to serratus posterior supe- clinical neurology as a guide to identify the location of pathology in
rior and is continuous with the superficial lamina of the deep cervical patients with peripheral sensory deficits, but it is important to remember
fascia on the back of the neck. In the thoracic region, the thoracolumbar that they are approximations (see Ch . 15) . (Adapted with permission from
fascia provides a thin fibrous covering for the extensor muscles of the Moffat DB 1993 Lecture Notes on Anatomy, 2nd edn . Oxford: Blackwell
vertebral column and separates them from the muscles connecting Scientific .)
the vertebral column to the upper extremity. Medially, it is attached to
the spines of the thoracic vertebrae, and laterally to the angles of the
ribs. In the lumbar region, the thoracolumbar fascia is in three layers thoracolumbar fasciae that have been implicated as a possible source


(Fig. 43.6; see Fig. 62.1). The posterior layer is attached to the spines of back pain include tissue deformation due to injury or immobility,
of the lumbar and sacral vertebrae and to the supraspinous ligaments. resulting in impaired proprioceptive signalling and possibly an increase
The middle layer is attached medially to the tips of the lumbar trans- in pain sensitivity, and increased sensitivity of the thoracolumbar fascia
verse processes and the intertransverse ligaments, below to the iliac in conditions involving other tissues innervated by the same spinal
crest, and above to the lower border of the twelfth rib and the lumbo- nerve (Willard et al 2012).
costal ligament. The anterior layer covers quadratus lumborum and is
attached medially to the anterior surfaces of the lumbar transverse pro-
cesses behind the lateral part of psoas major; below, it is attached to DEEP CERVICAL FASCIA
the iliolumbar ligament and the adjoining part of the iliac crest; above,
it forms the lateral arcuate ligament. The posterior and middle layers The investing layer of the deep cervical fascia forms the deep fascia of
unite to form a tough raphe at the lateral margin of erector spinae, and the posterior aspect of the neck (see Fig. 29.4A). It attaches in the
at the lateral border of quadratus lumborum they are joined by the midline to the external occipital protuberance, the ligamentum nuchae
anterior layer to form the aponeurotic origin of transversus abdominis. and the spine of the seventh cervical vertebra, and splits to enclose
At sacral levels, the posterior layer is attached to the posterior superior trapezius on each side. Inferiorly, the posterior part of the investing layer
iliac spine and posterior iliac crest, and fuses with the underlying erector attaches with trapezius to the spine and acromion of the scapula.
spinae aponeurosis. Bogduk (2005) describes two laminae in the pos-
terior layer at lumbar levels, with varying orientation of the constituent
BONES
collagen fibres relating to the biomechanical function of the fascia. The
posterior and middle layers of the thoracolumbar fascia and the verte-


bral column together form an osteofascial compartment that encloses OCCIPITAL BONE
the erector spinae muscle group.
The attachments of the fascia, especially those that assure continuity The occipital bone forms much of the back and base of the cranium
with the abdominal wall musculature, putatively give it an important (Fig. 43.7). It is trapezoid and internally concave, and encloses the
role in lifting, though the exact details of this role remain controversial. foramen magnum. It has four parts: basilar (basioccipital), which is the
The fascia may also play an important role in load transfer between the quadrilateral part in front of the foramen magnum; squamous, which
trunk and the limbs: its tension is affected by the actions of latissimus is the expanded plate posterosuperior to the foramen; and two lateral
dorsi, gluteus maximus and the hamstrings. Additionally, the thoraco- (condylar or exoccipital), one on each side of the foramen magnum.
lumbar fascia contains nociceptive nerve endings that may be respon- The latter is anteromedian and wider behind, with an anteroposterior
sible for some forms of back pain. Other mechanisms related to the diameter greater than its transverse diameter.


BACk
712
5
NOITCES Intercostal arteries – medial dorsal cutaneous branches
Intercostal arteries – lateral dorsal cutaneous branches
Lumbar arteries – medial dorsal cutaneous branches
Lumbar arteries – lateral dorsal cutaneous branches Fig .43 .5 Cutaneous lymphatics on the dorsum of the trunk . (With
permission from Romanes GJ (ed) 1964 Cunningham’s Textbook of
Sacral arteries
Anatomy, 10th edn . London: Oxford University Press .)
Circumflex scapular artery – horizontal and parascapular branches
Deep branch of transverse cervical artery/dorsal scapular artery
accommodate the cerebellar hemispheres. A wide groove with raised
Superficial branch of transverse cervical artery/superficial cervical artery banks, the superior sagittal sulcus, ascends from the protuberance to
Musculocutaneous perforators through latissimus dorsi arising from the the superior angle of the squamous part. The posterior part of the falx
intercostal and lumbar arteries cerebri is attached to the margins of the sulcus. A prominent internal
occipital crest descends from the protuberance and bifurcates near the
Fig .43 .4 Areas of cutaneous arterial supply on the dorsum of the trunk .
foramen magnum, and provides an attachment for the falx cerebelli.
(Redrawn with permission from Cormack GC, Lamberty BGH 1994 The
The occipital sinus, sometimes double, lies in this attachment. A small
Arterial Anatomy of Skin Flaps . Edinburgh: Churchill Livingstone .)
vermian fossa may exist at the lower end of the internal occipital crest;
when present, it is occupied by part of the inferior cerebellar vermis.
On each side, a wide sulcus for the transverse sinus extends laterally
The occipital bone provides attachment for a number of the muscles
from the internal occipital protuberance; the tentorium cerebelli is
of the neck and upper part of the back (longus capitis; recti capitis
attached to the margins of these sulci. The right sulcus is usually larger
anterior, lateralis, posterior major and minor; superior oblique; semi-
than the left, and passes into the sulcus for the superior sagittal sinus,


spinalis capitis; splenius capitis; occipitofrontalis; trapezius; sternoclei-
whereas the left usually receives the straight sinus. The position of the
domastoid), and articulates with the first cervical vertebra at the
confluence of the sinuses is indicated by a depression on one side of
atlanto-occipital joints.
the protuberance.
The position of the fetal posterior fontanelle coincides with the
Squamouspart
junction between the superior angle of the squamous part of the occipi-
tal bone and the occipital angle of the parietal bone on either side. The
The squamous part is an expanded plate posterosuperior to the foramen lateral angles of the squamous part are marked internally by the ends
magnum, convex externally and concave internally. On its external of the transverse sulci and project between the parietal and temporal
surface, the external occipital protuberance lies midway between its bones. The lambdoid borders extend from superior to lateral angles and
summit and the foramen magnum. On each side, two curved lines are serrated for articulation with the occipital borders of the parietal
extend laterally from this protuberance. The upper one, faintly marked bones at the lambdoid suture. The mastoid borders extend from the
and often almost imperceptible, is the highest nuchal line, and the lateral angles to the jugular processes, articulating with the mastoid
lower one is the superior nuchal line. The epicranial aponeurosis is parts of the temporal bones. A variety of sutural bones (ossicles) may
attached to the medial part of the highest nuchal line. The median occur at or near the lambda, e.g. the ‘interparietal’ (Inca bone or ossicle
external occipital crest is often faint; it descends from the external of Goethe).
occipital protuberance to the foramen magnum. On each side, an infe-
rior nuchal line spreads laterally from the midpoint of the crest. Muscle attachments The occipital part of occipitofrontalis is
The internal surface of the squamous part is divided into four deep attached to the lateral part of the highest nuchal line (see Fig. 43.7C).


fossae by an irregular internal occipital protuberance and by ridged Trapezius attaches to the medial third of the superior nuchal line and
sagittal and horizontal extensions from the protuberance. The two supe- to the external occipital protuberance. Sternocleidomastoid attaches to
rior fossae are triangular and adapted to the occipital poles of the cere- the lateral half of the superior nuchal line, with splenius capitis just
bral hemispheres; the inferior fossae are quadrilateral and shaped to below the lateral third of that line. Semispinalis capitis is attached to


Bones
713
34
RETPAHC
Transverse process of lumbar vertebra Thoracolumbar fascia, posterior layer Fig .43 .6 Muscles and fasciae of
the posterior abdominal wall .
Thoracolumbar fascia, middle layer
Erector spinae
Lateral raphe
Thoracolumbar fascia,
anterior layer
Latissimus dorsi
Quadratus lumborum
Iliacus Psoas major
Transversus abdominis
Anterior superior iliac spine Internal oblique
Psoas sheath
External oblique
the medial part of the area between the superior and inferior nuchal starts internally a little above the anterolateral part of the foramen
lines; obliquus capitis superior attaches to the lateral part of this area. magnum and continues anterolaterally. It may be partly or wholly
Rectus capitis posterior major attaches to the lateral part of the inferior divided by a spicule of bone and transmits the hypoglossal nerve and
nuchal line and to the bone immediately below, and rectus capitis a meningeal branch of the ascending pharyngeal artery. A condylar
posterior minor attaches to the medial part of the inferior nuchal line fossa, behind each condyle, fits the posterior margin of the superior
and to the bone between that line and the foramen magnum. facet of the atlas vertebra in full extension of the skull. Its floor is some-
times perforated by a posterior condylar canal for a sigmoid emissary
Basilarpart vein. A quadrilateral plate, the jugular process, projects laterally from
the posterior half of each condyle, and contributes the posterior part of
the jugular foramen. The jugular process is indented in front by a
The basilar part extends anterosuperiorly from the foramen magnum.
jugular notch, which may be partly divided by a small intrajugular
In young skulls, it presents a rough and uneven surface where it is
process projecting anterolaterally. A paramastoid process sometimes
joined to the body of the sphenoid by a growth cartilage (spheno-
projects downwards and may even articulate with the transverse process
occipital synchondrosis). This plate has fully ossified by the twenty-fifth


of the atlas vertebra. Laterally, the jugular process has a rough quadri-
year, at which time the occipital and sphenoid bones are fused.
lateral or triangular area that is joined to the jugular surface of the
The inferior surface bears a small pharyngeal tubercle, about 1 cm
temporal bone by cartilage; it begins to ossify at around 25 years.
in front of the foramen magnum, which gives attachment to the fibrous
An oval jugular tubercle overlies the hypoglossal canal on the supe-
pharyngeal raphe. A small depression immediately anterior to the
rior surface of the occipital condyle. Its posterior part often bears a
occipital condyle may occasionally be replaced by a small precondylar
shallow furrow for the glossopharyngeal, vagus and accessory nerves. A
tubercle. The anterior atlanto-occipital membrane is attached to the
deep groove containing the end of the sigmoid sinus curves anteromedi-
anterior margin of the foramen magnum.
ally around a hook-shaped process to end at the jugular notch. The
The superior surface has the form of a broad groove that slopes
posterior condylar canal opens into the posterior cranial fossa near the
upwards and forwards from the foramen magnum, directly into the
medial end of the groove.
basilar part of the sphenoid; together, these bones form the clivus. The
lateral margins articulate below with the petrous part of the temporal
MuscleattachmentsRectus capitis lateralis attaches to a roughened
bones.
area on the inferior surface of the jugular process (see Fig. 43.7C).
MuscleattachmentsLongus capitis is attached anterolateral to the
pharyngeal tubercle, and rectus capitis anterior is attached to the small Ossification
depression anterior to the occipital condyle (see Fig. 43.7C).
Above the highest nuchal lines, the squamous part of the occipital bone
Lateral(condylar)parts
is developed in a fibrous membrane and is ossified from two centres
(one on each side) from about the second fetal month. This part of


The lateral (condylar) parts of the occipital bone flank the foramen the occipital bone may remain separate as the interparietal bone. The
magnum. On their inferior surfaces are occipital condyles for articula- remainder of the occipital bone is preformed in cartilage. Below the
tion with the superior articular facets of the atlas vertebra. The condyles highest nuchal lines, the squamous part ossifies from two centres
are oval or reniform, their long axes converging anteromedially. The that appear in about the seventh week and soon unite. The two com-
articular surfaces, wholly convex, face inferolaterally. They are occasion- ponents of the squamous part unite in the third postnatal month but
ally constricted and a condyle may be in two parts (as may be the the line of their union is recognizable at birth. The remainder of the
reciprocal surfaces of the atlas vertebra). A tubercle gives attachment to cartilage of the occipital bone is ossified from five centres: two each for
an alar ligament medial to each articular facet. The hypoglossal (ante- the lateral parts appear during the eighth week, and one for the basilar
rior condylar) canal, which is situated anteriorly above each condyle, part appears around the sixth week.