a 56-year - old man was observed in the emergency room ( er ) 4050  min after the onset of acute de - novo stabbing , pulsating and diffuse headache with subsequent appearance ( within few minutes ) of dysarthria , postural instability with retropulsion , mild objective vertigo and vomiting , acral paresthesias of upper limbs , minimal confusional state without loss of consciousness or seizures .
neurological examination was relevant for reagent anisocoria ( left smaller than right ) , slight speech disorder ( dysarthria ) , retropulsion , moderate bilateral incoordination at the index - nose test , absence of fever and meningeal signs .
blood pressure ( bp ) was unstable with recurrent hypertensive crises ( 200/120  mmhg ) during observation , in the absence of definite previous history of hypertension as well as of diabetes , headache , or cardiovascular problems .
electrocardiographic monitoring excluded paroxysmal arrhythmias , while cardiac enzymes and creatine - kinase were negative . in the er , he was started on intravenous ( i.v . )
nimodipine ( 2  mg / hour ) with progressive normalization of bp values within 4  h. urgent brain computerized tomography ( ct ) was negative for hemorrhage and focal lesions . considering the unstable bp and the low nihss ( national institutes of health stroke scale ) score ( =3 ) at presentation , i.v .
thrombolysis for possible brainstem ischemia was excluded , and the patient was put on antiplatelet therapy with salicylic acid ( i.v .
250  mg for 24  h , followed by oral administration ) as for a minor ischemic events . under i.v .
salicylic acid , headache severity gradually decreased over the next 3  h , leaving only a slight diffuse , pulsating pain which remitted over the next 6  h. all the neurological signs and symptoms had completely recovered within 12  h. in order to investigate the vertebro - basilar ( vb ) district , the patient also underwent urgent brain ct - angiography with maximum intensity projection ( mip ) , multiplanar ( mp ) and three - dimensional ( 3d ) reconstructions , with the detection of left persistent primitive hypoglossal artery ( ppha ) as a large vessel originating from the internal carotid artery ( ica ) at the c2 vertebral level , entering the posterior cranial fossa through an enlarged hypoglossal canal and thus joining the lower portion of the basilar artery ( fig .  1 ) .
the study was then completed through 3d volume - rendering ( vr ) reconstructions for a better definition of the anatomical details ( fig .  1 ) .
collateral findings were represented by bilateral vertebral artery hypoplasia together with a small saccular aneurysm ( not - surgical ) of the anterior communicating artery , confirmed by digital subtraction angiography ( dsa ) which revealed no additional vascular abnormalities .
brain magnetic resonance ( mr ) with mr - diffusion weighted imaging ( mr - dwi ) was performed 24  h after onset of symptoms and did not show recent ischemic lesions .
the electroencephalogram  performed 12  h after admission  did not record epileptic / focal abnormalities .
uncommon causes of stroke ( thrombophilia , patent foramen ovale and other relevant metabolic risk factors for stroke ) were excluded during the course of the observation.fig . 
1a axial brain ct - angiography , b , c mip and 3d - reconstruction ct - angiography showing left ppha ( arrows ) .
d three - dimensional - vr ct - angiography showing ppha ( arrow ) entering the posterior cranial fossa through an enlarged hypoglossal canal and thus joining the lower portion of the basilar artery , and in e ppha ( arrow ) as a large vessel originating from the internal carotid artery at the c2 vertebra level a axial brain ct - angiography , b , c mip and 3d - reconstruction ct - angiography showing left ppha ( arrows ) .
d three - dimensional - vr ct - angiography showing ppha ( arrow ) entering the posterior cranial fossa through an enlarged hypoglossal canal and thus joining the lower portion of the basilar artery , and in e ppha ( arrow ) as a large vessel originating from the internal carotid artery at the c2 vertebra level the patient was then discharged with ramipril ( 5  mg per day ) plus oral salicylic acid ( 100  mg per day ) and at the 6-month control no further episode of headache  with or without neurological symptoms  was reported .
headache associated to vb signs and symptoms , once excluded critical conditions , could suggest at least four possible diagnoses : ( 1 ) basilar - type migraine , ( 2 ) posterior reversible encephalopathy syndrome ( pres ) , ( 3 ) headache attributed to benign ( or reversible ) angiopathy of the central nervous system , and ( 4 ) headache attributed to transient ischemic attack ( tia ) or minor stroke , whose diagnostic criteria are summarized in table  1.table  1diagnostic criteria for basilar - type migraine , posterior reversible encephalopathy syndrome ( pres ) , headache attributed to benign ( or reversible ) angiopathy of the central nervous system , and headache attributed to transient ischemic attack ( tia)basilar - type migraine migraine with aura symptoms clearly originating from the brainstem and/or from both hemispheres simultaneously affected , but no motor weakness(a ) at least 2 attacks fulfilling criteria b 
d(b ) aura consisting of at least two of the following fully reversible symptoms , but no motor weakness : dysarthria , vertigo , tinnitus , hypacusia , diplopia , visual symptoms simultaneously in both temporal and nasal fields of both eyes , ataxia , decreased level of consciousness , simultaneously bilateral paraesthesias(c ) at least one of the following :  ( 1 ) at least one aura symptom develops gradually over  5  min and/or different aura symptoms occur in succession over  5  min  ( 2 ) each aura symptom lasts  5 and  60  min(d ) headache fulfilling criteria b 
d for 1.1 migraine without aura begins during the aura or follows aura within 60  min(e ) not attributed to another disorderposterior reversible encefalophathy syndrome ( pres ) acute or subacute neurologic presentation of headeache , nausea , vomiting , altered mental function , seizures , stupor , visual disturbancesradiological hallmarks : reversible bilateral subcortical and cortical edema with a predominantly posterior distribution ( parieto - occipital ) at fluid - attenuated inversion recovery ( flair ) mri imagingheadache attributed to benign ( or reversible ) angiopathy of the central nervous system ( a ) diffuse , severe headache of abrupt or progressive onset , with or without focal neurological deficits and/or seizures and fulfilling criteria c and d(b )  strings and beads 
appearance on angiography and subarachnoid hemorrhage ruled out by appropriate investigations(c ) one or both of the following :  ( 1 ) headache develops simultaneously with neurological deficits and/or seizures  ( 2 ) headache leads to angiography and discovery of  strings and beads 
appearance(d ) headache ( and neurological deficits , if present ) resolves spontaneously within 2  monthsheadache attributed to transient ischemic attack ( tia ) ( a ) any new acute headache fulfilling criteria c and d(b ) focal neurological deficit of ischemic origin lasting  <  24  h(c ) headache develops simultaneously with onset of focal deficit(d ) headache resolves within 24  h diagnostic criteria for basilar - type migraine , posterior reversible encephalopathy syndrome ( pres ) , headache attributed to benign ( or reversible ) angiopathy of the central nervous system , and headache attributed to transient ischemic attack ( tia ) according to the current criteria of the international classification of headache disorders2nd ed .
( ichd - ii ) , our case potentially fulfills only some of the diagnostic criteria for basilar - type migraine (  1.2.6  ) : headache , dysarthria , vertigo ( with onset / worsening in few minutes ) , ataxia , decreased level of consciousness and simultaneous bilateral paraesthesias .
however , the neurological symptoms have lasted over 60  min and were associated with de - novo headache ( first episode ) , thus excluding the above hypothesis ( table  1 ) .
the second diagnosis we have considered , is pres , a rare and still poorly understood condition characterized by acute or subacute headache ( usually thunderclap type ) , nausea , vomiting , altered mental function , seizures , stupor and/or visual disturbances , with the radiological hallmarks of reversible bilateral subcortical and cortical edema with a predominantly posterior distribution ( parieto - occipital ) at fluid - attenuated inversion recovery ( flair)-mr sequences .
pres has been described in association with hypertensive encephalopathy , immunosuppressive and cytotoxic medications , puerperal eclampsia , collagen disease , renal failure , thrombotic thrombocytopenic purpura , human immunodeficiency virus infection , acute intermittent porphyria , and organ transplantation . in our case ,
the lack of the typical mr findings and the negative electroencephalogram tend to rule out this diagnosis .
headache attributed to benign ( or reversible ) angiopathy of the central nervous system  ( ichd - ii 
6.7.3  ) . in our case , despite the complete reversibility of all neurological signs , the lack of the radiological hallmarks  strings and beads  and the full headache recovery within 12  h , excludes this nosological entity ( table  1 ) .
the last possible and more suitable diagnosis is that of  headache attributed to transient ischemic attack ( tia)ichd - ii  6.1.2 
in fact , headache occurs frequently in patients with acute cerebrovascular disorders with a frequency  according to different studies  ranging from 7 to 65% .
several authors have stressed the greater incidence of headache among patients with ischemic events , particularly vb infarcts , due to the anatomical relationship between the posterior circulation and the trigeminal system .
although relatively less frequent during tia , sudden and acute headache of unknown cause , associated to dizziness or loss of balance , may represent a warning sign of vb failure .
the most common symptoms of extracranial vertebral artery involvement are represented by dizziness , blurred vision and imbalance , while vertigo is more typical of intracranial vertebral artery disease .
on the other hand , tia due to basilar artery failure produces , more frequently , dizziness , double vision , dysphagia , slurred speech and unilateral / bilateral weakness .
symptoms and signs due to tia ( either carotid or vb ) must resolve  by definition  within 24  h but sometimes they may be very brief  lasting few minutes  probably due to sudden and temporary bp failure . in this perspective , sacco et al .
have suggested to review the ichd - ii diagnostic criteria for  6.1.2  in the agreement with the new definition of tia proposed by the american heart association study group .
accordingly , tia is now defined as  a transient episode of neurological dysfunction caused by focal brain , spinal cord or retinal ischemia , without acute infarction  thus reducing the importance of the traditional temporal criterion for the definition of tia ( duration < 24  h ) . as a consequence ,
brain - mr imaging becomes now the crucial recommended tool for tia diagnosis . besides the above conditions discussed in the differential diagnosis versus the most probable hypothesis of  headache attributed to transient ischemic attack ( tia ) or minor stroke  , we can also exclude ichd - ii 
10.3.2  ( headache attributed to hypertensive crisis without hypertensive encephalopathy ) , due to the presence of long - lasting focal neurological signs .
in the present case , de - novo acute headache and transient ischemia in the posterior circulation are associated with the evidence of ppha , a rare vascular anomaly of the posterior circulation that ensures a pathological anastomosis between carotid and basilar system . at the intracranial level , four embryonic arteries ( trigeminal , otic , hypoglossal and proatlantal )
participate to the vb development : once completed , these vessels gradually regress , but in some cases they may persist . the detection is often fortuitous during angiographic examination .
the trigeminal artery is generally associated with disorders of the 3rd , 4th , 5th and 6th cranial nerves , while the otic artery may cause acoustic or facial nerves palsy .
the hypoglossal artery may lead to 12th nerve palsy , glossopharingeal neuralgia or vascular disorders in the posterior circulation .
it originates as a branch of the cervical part of the ica between c1 and c3 levels , passes through the hypoglossal canal and joins the lower portion of the basilar artery after a tortuous course .
consequently , any significant alteration of the blood flow in the proximal ica may affect the posterior circulation with possible reversible vb symptoms .
less frequent  is usually associated to ischemic lesions . from a pathogenetic point of view
, it seems therefore reasonable to consider , in our case , the particular vulnerability of the posterior circulation due to the ppha , the associated vascular abnormalities , and its possible secondary , transient , hemodynamic failure during hypertensive phases .
our clinical picture may be classified as a real tia of the posterior circulation , also considering the complete clinical recovery within 24  h and the absence of ischemic lesions ( including lacunar events ) on mr investigations .
moreover , the headache presented by the patient , meets the ichd - ii diagnostic criteria for  headache attributed to transient ischemic attack ( tia)subgroup  6.1.2  . in conclusion , the persistence of carotid - basilar anastomoses ,
although rare entities , must be considered not only in patients with isolated or combined cranial nerve deficit , but also in the presence of cerebrovascular events involving the vb system .
their association with other vascular abnormalities ( hypoplasia ) can confer increased vulnerability to other factors ( hypertension ) as in the present case .
 we report the case of a 56-year - old man with acute onset of de - novo stabbing , pulsating and diffuse headache with subsequent appearance ( within few minutes ) of posterior fossa symptoms ( vomiting , postural instability , anisocoria , incoordination , dysarthria , retropulsion ) lasting 912  h. recurrent hypertensive crises were detected during the acute observation in the emergency room , even in the absence of previous history of hypertension . 
 once subarachnoid hemorrhage and focal lesions ( vascular and non - vascular ) were excluded , brain computerized tomography - angiography and digital subtraction angiography disclosed the presence of left persistent primitive hypoglossal artery with bilateral vertebral artery hypoplasia and a slight aneurysmal dilation of the anterior communicating artery . 
 brain magnetic resonance study performed 24  h after onset of symptoms was negative for recent ischemic lesions . 
 the clinical features of this rare vascular condition are discussed as a possible cause of magnetic resonance ( diffusion weighted imaging ) negative vertebro - basilar transient ischemic attack . 
Case report
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