CASE REPORT An obscure cause of stroke - basilar artery fenestration M Hoffmann MBBCh, FCP(SA)Neuro D Royston* MBChB,FFRad(D)SA PCorr* MBCM, FFRad(D)SA, FRCR, MMed(UCT) Departments of Neurology, 'Radiologyand Vascular Surgery, University of Natal, Durban. Introduction Cerebral artery fenestrations or in- travascular bridges represent develop- mental anomalies, that may be inciden- tal findings but sometimes of clinical significance.' These embryological ab- normalities may also take the form of duplication of an artery. For the basilar artery, the incidence has been cited as 5.3% for the general population," the most frequently involved intracerebral arterial system being the vertebrobasilar system." The most important consequence is the tendency to develop arterial aneurysms at the site of fenestrations with a 3% incidence in a retrospective analysis of 5 190 angiograms." Current pathophysiologi- cal data has shown that medial defects of the arterial walls predispose to an- eurysm formation. Fenestrations have been described in the basilar, verte- bral, middle cerebral, anterior cerebral, aortic arch and posterior cerebral arteries.l/ In addition to a propensity to form aneurysms, a number of other neurological presentations have been described in association with fenestrations including cerebral ischae- mia,S,6,7trigeminal neuralgia," cervical myelopathy? and symptomatic arterio- venous malformations.'? Case report A 71 year-old white man suffered progressively more debilitating attacks of dizziness, diplopia, imbalance and inco-ordination over a seven year pe- riod with several daily attacks occur- ring at time of presentation. History He first reported intermittent diplo- pia eight years prior to presentation, lasting about 90 minutes. A second at- tack occurred nine months later. He was seen by his general practitioner and ophthalmologist at the time with no abnormality noted. One year later the attacks increased in frequency to one every few months culminating in a much more severe attack with dizzi- ness lasting two hours but without ab- normality seen on a MRI scan. During the next four years the diplopia in- creased dramatically varying from un- der one minute up to 30 minutes and could occur up to seven times per day. 22 SA JOURNAL OF RADIOLOGY. May 1998 An episode occurred subsequently with dysphasia, imbalance and dizziness last- ing about 30 minutes but with com- plete return to normality. A second MR! brain scan done at the time was normal. He was given various diagnoses such as transient ischaemie attacks and migraine by different neurologists. An even more disabling attack occurred six years after his first symptoms wherefrom he awoke with speech im- pairment, inability to walk, loss of co- ordination and difficulty in handling objects. This time a stroke was diag- nosed and he improved again only to have a marked exacerbation of his symptoms one month later with inter- mittent attacks of a similar nature oc- curring 2-3 times per day lasting about between 30-60 minutes. He was quite disabled by these and described the left sided image (referring to his diplopia) as "coming and going all the time". The most recent presentation was associ- ated with almost continuous diplo- pia and dizziness. He was otherwise in good health and had no cerebrov- ascular or cardiovascular risk factors, no deleterious habits and no general or neurological illness. Examination Examination revealed a rational man of normal body habitus with a BP of 145/90 and a pulse of 68 per minute regular. The cardiac, chest and abdomi- nal examinations were normal and no stigmata of generalized disease were noted. No cervical or supraclavicular bruits were heard. Neurologically higher functions and cranial nerves were normal. Motor testing was nor- mal save for bilateral upper limb rela- tive hyperreflexia, left more than right. Sensation and limb co-ordination were normal and gait markedly ataxic with tandem gait impossible. to page 23 An obscure cause of stroke - basi lar artery fenestration from page 22 Clinical assessment The clinical assessment included a differential of posterior circulation is- chaemia and/or infarction due to vertebrobasilar vascular abnormality. Investigations Routine blood tests, prothrombotic screen, chest radiograph and electrocar- diogram were normal. Doppler sonography of the cervicocephalic and intracranial vessels was normal. Echocardiography and coronary angi- ography were normal. The third MRI brain scan was also normal. Cerebral MR angiography proved diagnostic in that a proximal basilar artery fenestration was seen. This was first suspected due to the presence of a dilated mid basilar section with intra- vascular hypointense signal (Figure 1). Figure 1: Magnetic resonance angiogram of the vertebrobasilar arteries. A dilatation of the mid basilar artery with an intravascu- lar hypointense signal (arrow). A trans axial magnetic resonance angi- ogram revealed a biconcave appearance of the basilar artery typical of a fenes- tration (Figure 2). Functional brain scanning with SPECT brain, revealed bi-occipito-parietal hypoperfusion. Management He was initially treated with War- farin without relief of symptoms. Subsequent treatment with Aspirin Figura 2: Transaxial magnetic resonance angiogram revealing the biconcave appearance of the basilar artery typical of a fenestration (arrow). alleviated some of the symptoms which further decreased with the ad- dition of Persantin. Discussion Recognition of cerebral artery fenestrations in the context of cerebral ischaemia or stroke is important for at least three reasons:" 1. It may represent the mechanism for the ischaemia or stroke. 2. Various treatment options are avail- able which include medical, interven- tional radiological (Guglielmi coils) 11 and surgical options such as aneurysm clipping. The realisation that aneu- rysms may be part of this develop- mental abnormality should demand a comprehensive appraisal of the cer- ebral circulation by angiography. 3. A precise diagnosis as early as pos- sible will also save unnecessary costly investigations (in this patient three MRI scans) and guide appropriate therapy. In the case under discussion, pre- sumably turbulent blood flow at the site of the fenestration lead to in situ thrombosis with distal embolisation and/or intermittent haemodynamic disturbances. This scenario is espe- cially likely in that all other causes of posterior circulation ischaemia were 23 SA JOURNAL OF RADIOLOGY. May 1998 excluded by a comprehensive stroke work up. In this patient Warfarin failed to alleviate symptoms whereas antiaggregant therapy led to a marked improvement. 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