arachnoid cyst

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1. bladder.
2. an abnormal closed epithelium-lined sac in the body that contains a liquid or semisolid substance. Most are harmless, but they should be removed when possible because they occasionally may change into malignant growths, become infected, or obstruct a gland. There are four main types of cysts: retention cysts, exudation cysts, embryonic cysts, and parasitic cysts.
3. a stage in the life cycle of certain parasites, during which they are enveloped in a protective wall.
adventitious cyst pseudocyst (def. 1).
alveolar c's dilatations of pulmonary alveoli, which may fuse by breakdown of their septa to form large air cysts (pneumatoceles).
arachnoid cyst a fluid-filled cyst between the layers of the leptomeninges, lined with arachnoid membrane, usually in the sylvian fissure.
Baker cyst a swelling on the back of the knee, due to escape of synovial fluid that has become enclosed in a sac of membrane.
Bartholin cyst a mucus-filled cyst of a Bartholin gland, usually developing as a consequence of an obstruction of the duct by trauma, infection, epithelial hyperplasia, or congenital atresia or narrowing.
Blessig c's cystic spaces formed at the periphery of the retina.
blue dome cyst
1. a benign retention cyst of the breast that shows a pale blue color. See also cystic disease of breast.
2. a cyst due to endometriosis, found in healed wounds such as those of an episiotomy or an incision for a cesarean section; it is usually found in the vaginal fornix or on the cervix.
Boyer cyst an enlargement of the subhyoid bursa.
branchial cyst (branchiogenic cyst) (branchiogenous cyst) see branchial cyst.
bronchogenic cyst a congenital cyst, usually in the mediastinum or lung, arising from anomalous budding during formation of the tracheobronchial tree, lined with bronchial epithelium that may contain secretory elements.
chocolate cyst one filled with hemosiderin, causing a dark color, following local hemorrhage, such as may occur in the ovary in ovarian endometriosis.
choledochal cyst a congenital cystic dilatation of the common bile duct, which may cause pain in the right upper quadrant, jaundice, fever, or vomiting, or be asymptomatic.
daughter cyst a small parasitic cyst developed from the walls of a larger cyst.
dentigerous cyst an odontogenic cyst surrounding the crown of a tooth, originating after the crown is completely formed.
dermoid cyst see dermoid cyst.
duplication cyst a congenital cystic malformation of the alimentary tract, consisting of a duplication of the segment to which it is adjacent, occurring anywhere from the mouth to the anus but most frequently affecting the ileum and esophagus.
echinococcus cyst hydatid cyst.
embryonic cyst one developing from bits of embryonic tissue that have been overgrown by other tissues, or from developing organs that normally disappear before birth. An example is a branchial cyst.
enteric cyst (enterogenous cyst) a cyst of the intestine arising or developing from some fold or pouch along the intestinal tract. Called also enterocyst and enterocystoma.
epidermal cyst (epidermoid cyst) an intradermal or subcutaneous cyst containing keratinizing squamous epithelium; it arises from occluded hair follicles. Called also wen.
epidermal inclusion cyst a type of epidermal cyst occurring on the head, neck, or trunk, formed by keratinizing squamous epithelium with a granular layer.
epithelial cyst
1. any cyst lined by keratinizing stratified squamous epithelium, found most often in the skin.
exudation cyst a cyst formed by the slow seepage of an exudate into a closed cavity.
false cyst pseudocyst (def. 1).
follicular cyst one due to occlusion of the duct of a follicle or small gland, especially one formed by enlargement of a graafian follicle as a result of accumulated transudate.
hydatid cyst the larval stage of the tapeworms Echinococcus granulosis and E. multilocularis; each one contains daughter cysts that have many scoleces (mouths). See also hydatid disease. Called also echinococcus cyst and hydatid.
inclusion cyst one formed by the inclusion of a small portion of epithelium or mesothelium within connective tissue along a line of fusion of embryonic processes; several types are found in the oral and nasal regions.
keratinizing cyst one arising in the pilosebaceous apparatus, lined by stratified squamous epithelium and containing largely macerated keratin and often sufficient sebum to render the contents greasy or rancid.
meibomian cyst chalazion.
mucus retention cyst a mucus-containing retention cyst caused by blockage of a salivary gland duct.
multilocular cyst
1. a cyst containing several loculi or spaces.
2. a hydatid cyst with many small irregular cavities that may contain scoleces but generally little fluid.
3. a thick-walled cyst in the kidney, found in clusters and usually unilaterally. In children it contains blastema and may develop into a Wilms tumor.
myxoid cyst a nodular lesion usually overlying a distal interphalangeal finger joint in the dorsolateral or dorsomesial position, consisting of focal mucinous degeneration of the collagen of the dermis; not a true cyst, lacking an epithelial wall, it does not communicate with the underlying synovial space.
Naboth's c's (nabothian c's) cysts that occur when mucus-producing glands in the columnar epithelium of the uterine cervix become covered over by squamous epithelium resulting from metaplasia; they are usually found in the transformation zone of the cervix. Called also Naboth's or nabothian follicles.
nasoalveolar cyst (nasolabial cyst) a fissural cyst arising outside the bones at the junction of the globular portion of the medial nasal process, lateral nasal process, and maxillary process.
odontogenic cyst one derived from epithelium, usually containing fluid or semisolid material, which develops during various stages of odontogenesis; nearly always enclosed within bone.
parasitic cyst one forming around larval parasites (tapeworms, amebas, trichinae), such as a hydatid cyst.
periapical cyst a periodontal cyst involving the apex of an erupted tooth.
perineurial cyst an outpouching of the perineurial space on the extradural portion of the posterior sacral or coccygeal nerve roots at the junction of the root and ganglion; it may cause low back pain and sciatica.
periodontal cyst one in the periodontal ligament and adjacent structures, usually at the apex of the tooth (periapical cyst).
pilar cyst a type of epidermal cyst, almost always found on the scalp, arising from the outer root sheath of the hair follicle.
pilonidal cyst see pilonidal cyst.
radicular cyst an epithelium-lined sac at the apex of a tooth.
Rathke's c's (Rathke's cleft c's) groups of epithelial cells forming small colloid-filled cysts in the pars intermedia of the pituitary gland; they are vestiges of Rathke's pouch and are closely related to craniopharyngiomas.
retention cyst a tumorlike accumulation of a secretion formed when the outlet of a secreting gland is obstructed. These cysts may develop in any of the secretory glands, such as the breast, pancreas, kidney, salivary or sebaceous glands, or mucous membranes.
sarcosporidian cyst sarcocyst (def. 2).
sebaceous cyst see sebaceous cyst.
solitary bone cyst a pathologic bone space in the metaphyses of long bones of growing children; it may be either empty or filled with fluid and have a delicate connective tissue lining.
subchondral cyst a bone cyst within the fused epiphysis beneath the articular plate.
tarry cyst
1. one resulting from hemorrhage into a corpus luteum.
2. a bloody cyst resulting from endometriosis.
theca-lutein cyst a cyst of the ovary in which the cystic cavity is lined with theca cells.
traumatic bone cyst a cavity (not a true cyst) formed in bone, particularly the mandible, in response to trauma. The hematoma precipitated by trauma is resorbed but bone is not replaced; the space formed is usually empty and lacks an epithelial lining.
unicameral bone cyst solitary bone cyst.
wolffian cyst a cyst of the broad ligament developed from vestiges of the mesonephros.

a·rach·noid cyst

a fluid-filled cyst lined with arachnoid membrane, frequently situated near the lateral aspect of the lateral sulcus of cerebral hemisphere; usually congenital in origin.
Synonym(s): leptomeningeal cyst

a·rach·noid cyst

(ă-rak'noyd sist)
A fluid-filled cyst lined with arachnoid mater, frequently situated near the lateral aspect of the lateral sulcus; usually congenital in origin.

Patient discussion about arachnoid cyst

Q. What is the treatment for an arachnoid cyst? My 15 year old son has just been diagnosed with an arachnoid cyst. What is the treatment? Is an operation necessary?

A. An operation is not always necessary, it depends on the size and location of the cyst. I suggest you take your son to a neurologist or a neurosurgeon for further consult.



Q. info on arachnoid cyst in the right posterior fossa

A. Basically it's like a small sac filled with fluid. The problem is that the skull is a rigid closed space, which means that if there's something other than the brain, it'll occupy space, usually on expense of the brains' space. These kinds of problems are often referred to as "space occupying lesion".

It's usually congenital (i.e. develops during pregnancy), and even when it cause symptoms they develop slowly.

YOu can read more here (

More discussions about arachnoid cyst
References in periodicals archive ?
Cognitive improvement despite minimal arachnoid cyst decompression.
Arachnoid cyst with psychosis can be left untouched or resected as per the pressure symptoms.
A variety of intracranial lesions including gliomas, metastases, craniopharyngiomas, abscesses, parasitic cysts (such as cysticercosis), epidermoids and arachnoid cysts may appear as mainly cystic masses on magnetic resonance (MR) and computed tomography (CT) studies of the brain.
The ultrasound scan showed a non-communicating arachnoid cyst measuring 1.6 x 2.9 cm in the foetus.
Non-neoplastic causes include necrotizing granulomatous inflammation (6.5%), degenerated disc material (3.8%), fungal infection (3.2%), abscess (2.2%), dermoid cyst (2.2%), epidermoid cyst (1.6%), AV malformation (1.1%), arachnoid cyst (0.5%), colloid cyst (0.5%) and meningiocele (0.5%).
A total of 176 patients with hypothalamo-pituitary lesions (craniaopharyngioma, optic glioma, arachnoid cyst, hamartoma, germ cell tumour) were evaluated retrospectively.
Yamasaki, ""No-no" type bobble-head doll syndrome in an infant with an arachnoid cyst of the posterior fossa: a case report," Pediatric Neurology, vol.
Conclusion: The most common cerebellopontine angle tumor is acoustic neuroma which is followed by meningioma, epidermoid and arachnoid cyst. The most common presenting symptom is hearing loss which is followed by headache, tinnitus and disequilibrium.
After extensive medical workup for the etiology of her condition, there were no abnormalities to be found, with the exception of a left temporal lobe arachnoid cyst.
The differential diagnosis of cerebral hydatid cyst disease ranges from simple benign cysts such as porencephalic cyst and arachnoid cyst, infectious causes such as cavitary tuberculosis, mycoses, pyogenic abscesses, and finally cystic neoplasms.