New England Medical Center Posterior Circulation Stroke Registry: I. Methods, Data Base, Distribution of Brain Lesions, Stroke Mechanisms, and Outcomes

Among 407 New England Medical Center Posterior Circulation Registry (NEMC-PCR) patients, 59% had strokes without transient ischemic attacks (TIAs), 24% had TIAs before strokes, and 16% had only posterior circulation TIAs. Embolism was the commonest stroke mechanism accounting for 40% of cases (24% cardiac origin, 14% arterial origin, 2% had potential cardiac and arterial sources). In 32%, large artery occlusive lesions caused hemodynamic brain infarction. Stroke mechanisms in the posterior and anterior circulation are very similar. Infarcts most often included the distal posterior circulation territory (rostral brainstem, superior cerebellum and occipital and temporal lobes), while the proximal (medulla and posterior inferior cerebellum) and middle (pons and anterior inferior cerebellum) territories were equally involved. Infarcts that included the distal territory were twice as common as those that included the proximal or middle territories. Most distal territory infarcts were attributable to embolism. Thirty day mortality was low (3.6%). Embolic stroke mechanism, distal territory location, and basilar artery occlusive disease conveyed the worst prognosis.     

Bilateral intracranial vertebral artery disease in the New England Medical Center, Posterior Circulation Registry.

BACKGROUND: Previous studies of patients with bilateral intracranial vertebral artery (ICVA) disease were selective and retrospective. METHODS: We studied risk factors, vascular lesions, symptoms, signs, and outcomes in patients with bilateral ICVA disease among 430 patients in the New England Medical Center Posterior Circulation Registry. RESULTS: Forty-two patients had bilateral ICVA occlusive disease (18 had bilateral stenosis; 16, unilateral occlusion and contralateral stenosis; and 8, bilateral occlusion). The most common risk factors were hypertension (32/42 [76%]) and hyperlipidemia (22/42 [52%]). Sixteen patients (38%) had transient ischemic attacks (TIAs) only; 18 (43%), TIAs before stroke. Occlusive vascular disease also involved the basilar artery in 29 patients (69%), the extracranial vertebral arteries in 18 (43%), and the internal carotid arteries in 11 (26%). Only 6 patients had no other major vascular lesion. Cerebellar symptoms were common. Among 30 patients with infarction, 21 (70%) had proximal intracranial territory involvement, and 15 (50%) had distal territory involvement. The location of occlusive lesions in relation to posterior inferior cerebellar artery origins did not significantly influence prognosis. During follow-up, 31 patients had no symptoms or slight disability, 2 had progression, and 7 died. Among 7 patients with poor outcome, 6 also had basilar artery stenosis or occlusion and 5 had proximal and distal intracranial territory infarcts. CONCLUSIONS: Most patients with bilateral ICVA occlusive disease have hypertension, other major occlusive lesions, and TIAs before stroke. Short- and long-term outcomes are usually favorable, but patients with bilateral ICVA and basilar artery-occlusive lesions often have poor outcomes.     

The intracranial vertebral artery: a neglected species. The Johann jacob wepfer award 2012

Among posterior circulation arteries, the intracranial vertebral artery (ICVA) has been given the least attention, especially concerning treatment of occlusive lesions. Early clinicopathological studies showed that the ICVA was often occluded in patients with lateral medullary and posterior inferior cerebellar infarcts. Severe stenosis or occlusion of the ICVA was the most common arterial lesion among the 408 patients in the New England Medical Center Posterior Circulation Registry (NEMC-PCR). In this registry, the distal portion of the artery was most often involved, sometimes with spread into the basilar artery. ICVA occlusive lesions were often bilateral and very often accompanied by basilar and cervical vertebral artery occlusive lesions. Patients with bilateral ICVA occlusions often had attacks of dizziness, blurred vision, and ataxia during months and years but rarely later developed disabling infarction. Most posterior circulation infarcts in patients with ICVA occlusive lesions were located in the middle and distal posterior circulation territories and were rostral to the medulla and inferior cerebellum. Although diagnostic techniques now image the ICVA and its lesions well, the optimal treatment of patients with various ICVA occlusive lesions has very rarely been analyzed or reported. The therapeutics of patients with ICVA disease is uncharted territory and begs for attention and clarification.     

New England Medical Center Posterior Circulation Stroke Registry II. Vascular Lesions

Among 407 New England Medical Center Posterior Circulation Registry (NEMC-PCR) patients, the extracranial (ECVA) and intracranial vertebral arteries (ICVA) were the commonest sites of severe occlusive disease followed by the basilar artery (BA). Severe occlusive lesions were found in >1 large artery in 148 patients; 134 had unilateral or bilateral severe disease at one arterial location. Single arterial site occlusive disease occurred most often in the ECVA (52 patients, 15 bilateral) followed by the ICVA (40 patients, 12 bilateral) and the BA (46 patients). Involvement of the ICVAs and the BA was very common and some patients also had ECVA lesions. Hypertension, smoking, and coronary and peripheral vascular disease were most prevalent in patients with extracranial disease while diabetes and hyperlipidemia were more common when occlusive lesions were only intracranial. Intra-arterial embolism was the most common mechanism of brain infarction in patients with ECVA and ICVA occlusive disease. ICVA occlusive lesions infrequently caused infarction limited to the proximal territory (medulla and posterior inferior cerebellum). BA lesions most often caused infarcts limited to the middle posterior circulation territory (pons and anterior inferior cerebellum). Posterior cerebral artery occlusive lesions were predominantly embolic. Penetrating artery disease caused mostly pontine and thalamic infarcts. Prognosis was poorest in patients with BA disease. The best prognosis surprisingly was in patients who had multiple arterial occlusive lesions; they often had position-sensitive transient ischemic attacks during months or years.     

Embolism from vertebral artery origin occlusive disease.

We report 10 patients with severe occlusive disease of the vertebral artery (VA) origin in the neck with intra-arterial embolism to the posterior circulation. The VA lesions in seven patients were complete occlusions, and three patients had severe atherostenosis. All patients had strokes in the vertebrobasilar territory. The most frequent recipient sites of intra-arterial embolism were the intracranial VA-posterior inferior cerebellar artery region (8), and the distal basilar artery (BA) and its superior cerebellar and posterior cerebral artery branches (7). Two patients had pontine infarction due to BA embolism. The most common clinical signs were due to cerebellar infarction. Atherosclerotic disease of the VA origin has features in common with disease of the internal carotid artery origin. Both have similar risk factors and demography, and each can cause strokes by intracranial intra-arterial embolism.     

Clinical findings of intracranial vertebral artery disease using magnetic resonance angiography

The vertebral artery lesion has a variety of clinical characteristics. We sought to clarify the clinical patterns and the location of the intracranial vertebral artery (ICVA) diseases according to analyses of images obtained using magnetic resonance angiography (MRA). We studied vascular lesions, risk factors, symptoms, signs, and outcomes in 35 patients with ICVA disease (3 had bilateral occlusion; 9, unilateral occlusion; 6, bilateral stenosis; and 17, unilateral stenosis). The most common site of unilateral and bilateral lesions was the distal ICVA after the origin of posterior inferior cerebellar artery (PICA). We found accompanying basilar artery disease in 28.6% of patients with unilateral and bilateral ICVA disease. The majority of the ICVA lesions were associated with internal carotid arteries disease (48.8%). The common vascular risk factors were hypertension (71%), diabetes mellitus (34%), hyperlipidemia (31%), smoking (29%), and coronary artery disease (23%). Eighteen patients (51.4%) had transient ischemic attacks (TIAs) only, 10 patients (28.6%) had TIAs before stroke, and 5 patients (14.3%) had strokes without TIAs. Most patients (80%) with TIAs, with or without stroke, had multiple episodes. Vertigo or dizziness, ataxia, limbs weakness and abnormal gait were the common symptoms and signs. At 6 months follow-up, 66.7% patients had no symptoms or only slight symptoms that caused no disability. Our data showed (1) the usual location of ICVA disease (occlusion or severe stenosis) was distal to PICA, especially near the vertebrobasilar junction; (2) the risk factors were hypertension, diabetes mellitus, hyperlipidemia, smoking, and coronary artery disease; (3) patients with ICVA disease had a high frequency of accompanying internal carotid, middle cerebral, or basilar artery disease; (4) vertigo or dizziness, and ataxia were the common symptoms and signs; (5) TIA was the most common clinical pattern; (6) the outcome was favorable, except in cases with bilateral ICVA occlusion.     

Basilar artery stenosis: middle and distal segments

We report the clinical features and prognosis in nine patients with angiographically documented basilar artery stenosis of the middle and distal segments. Six patients had transient ischemic attacks (TIAs), and in two this was their only clinical manifestation. The TIAs in four patients included two or more of the following symptoms: dizziness, diplopia, perioral numbness, dysphagia, weakness, or loss of consciousness. Two other patients had isolated symptoms of transient dizziness and unilateral weakness. Seven patients had posterior circulation strokes, preceded by TIAs in four. Basilar artery occlusive disease can affect any segment of the artery. The short-term prognosis of middle and distal basilar artery stenosis was good especially when patients were treated with warfarin or platelet antiaggregants.     

Racial differences in the distribution of posterior circulation occlusive disease

We compared clinical and arteriographic features in 27 white and 24 black patients with symptomatic posterior circulation occlusive disease. The degree of arterial stenosis was measured independently by two examiners at 12 sites within the vertebrobasilar territory. Racial comparisons were made based upon the distribution of extra- and intracranial occlusive lesions and symptomatic sites of the lesions. White patients had significantly more angina pectoris, more lesions of the origin of the left vertebral artery and more high grade lesions of the extracranial vertebral arteries. Black patients had significantly higher mean diastolic blood pressure, more diabetes mellitus, more lesions of the distal basilar artery, more high grade lesions of intracranial branch vessels and more symptomatic intracranial branch disease. Race was found to be the only factor increasing the risk of intracranial posterior circulation occlusive disease. Knowledge of the contribution of race to the distribution of posterior circulation lesions will help guide evaluation and treatment strategies for patients with vertebrobasilar occlusive disease.     

Clinical features of proven basilar artery occlusion

Our study describes the early symptoms and signs of 85 patients with either basilar artery occlusion or bilateral distal vertebral artery occlusion documented by selective angiography. The most common prodromal symptoms were vertigo, nausea, and headache, which occurred during the 2 weeks before the stroke. Angiographic findings of 49 patients were classified into proximal, middle, and distal basilar artery occlusions. Twenty-two of these patients had additional vertebral artery lesions. A fourth group was composed of 36 patients with bilateral distal vertebral artery occlusion without opacification of the basilar artery through a vertebral artery injection. Onset was sudden in 20 patients; sudden, but preceded by prodromal symptoms in 11 patients; and progressive in 54 patients. Patients with progressive strokes often had bilateral vertebral artery occlusions. Most patients with acute onset had occlusion of the middle and distal basilar artery. An embolic origin of basilar artery occlusion from an arteriosclerotic vertebral artery lesion was assumed to be an important mechanism. An embolus reaching the basilar artery may not necessarily reach the top of the artery, but may also become lodged more proximally.     

小脑梗死的分型与后循环血管病变

目的 研究有无大血管病变患者小脑梗死灶的特征,探讨小脑梗死分型与后循环血管病变的关系。 方法 收集我科自2006年1月～2008年3月期间住院的小脑梗死患者共35例,所有患者均同时具备颅脑磁共振成像（magnetic resonance imaging,MRI）和血管造影检查,包括计算机断层摄影血管造影（computed tomographic angiography,CTA）、磁共振血管造影（magnetic resonance angiography,MRA）和数字减影血管造影（digital subtraction angiography,DSA）检查。根据血管造影检查的结果将入组患者分为两组：大血管病变组20例,小血管病变组15例,分析两组小脑梗死的分型和后循环血管病变（包括狭窄或闭塞）的关系。 结果 ⑴大血管病变组20例中,颅内血管（椎动脉颅内段或基底动脉）病变最多见（10例,50%）,梗死类型多为分水岭梗死（7例,70%）;其次为颅外血管合并颅内血管（椎动脉颅外段合并颅内段或基底动脉）病变（8例,40%）,梗死灶多为小脑后下动脉（PICA）供血区的区域性梗死（7例,87.5%）;单独颅外血管（椎动脉颅外段）病变最少见（2例,10%）,梗死分布无明显倾向性。⑵小血管病变组15例中,梗死灶亦多位于分水岭区（9例,60%）。 结论 由于小脑血液供应特点,小脑梗死中分水岭梗死和腔隙性梗死较区域性梗死更为常见。小梗死灶（直径≤2cm）可能存在后循环大血管的狭窄或闭塞,应予积极的治疗和干预,以防病情加重。     

Atherothrombotic cerebellar infarction: vascular lesion-MRI correlation of 31 cases.

BACKGROUND AND PURPOSE: Correlation of MRI findings with atherosclerotic vascular lesions has rarely been attempted in patients with cerebellar infarction. The aim of this study was to correlate the MRI lesions with the vascular lesions seen on conventional cerebral angiography in cerebellar infarction. METHODS: The subjects included 31 patients with cerebellar infarcts who underwent both MRI and conventional cerebral angiography. We analyzed the risk factors, clinical findings, imaging study, and angiography results. We attempted to correlate MRI lesions with the vascular lesions shown in the angiograms. RESULTS: The vascular lesions seen on angiograms were subdivided into 3 groups: large-artery disease (n=22), in situ branch artery disease (n=6), and no angiographic disease with hypertension (n=3). The proximal segment (V1) lesions of vertebral artery were the most common angiographic features in patients with large-artery disease in which stroke most commonly involved the posterior inferior cerebellar artery (PICA) cerebellum. The V1 lesions with coexistent occlusive lesions of the intracranial vertebral and basilar arteries were correlated with cerebellar infarcts, which had no predilection for certain cerebellar territory. The intracranial occlusive disease without V1 lesion was usually correlated with small cerebellar lesions in PICA and superior cerebellar artery (SCA) cerebellum. The subclavian artery or brachiocephalic trunk lesion was associated with small cerebellar infarcts. The in situ branch artery disease was correlated with the PICA cerebellum lesions, which were territorial or nonterritorial infarct. No angiographic disease with hypertension was associated with small-sized cerebellar infarcts within the SCA, anterior inferior cerebellar artery, or SCA cerebellum. CONCLUSIONS: Our study indicates that the topographic heterogeneity of cerebellar infarcts are correlated with diverse angiographic findings. The result that large-artery disease, in which nonterritorial infarcts are more common than territorial infarcts, is more prevalent than in situ branch artery disease or small-artery disease, suggest that even a small cerebellar infarct can be a clue to the presence of large-artery disease.     

多灶性后循环缺血患者的病灶分布与血管形态异常及近期预后分析

目的 观察多灶性后循环缺血患者的病灶分布和血管形态异常的特点,评估患者出院时的近期预后及其与病灶分布和血管形态的关系.方法 对34例经过MR/所证实的多灶性后循环缺血患者行主动脉弓及全脑血管DSA,全面分析病灶分布及血管形态异常的特点;同时对患者出院时的近期预后用改良Rankin分级(MRS)评分表进行评估,分析病灶分布及血管形态异常与近期预后的关系.结果 多灶性后循环缺血患者最常被累及的部位是脑桥(22例),最常被累及的区段是中段+远段(12例);34例患者中有26例(76.5%)DSA显示出血管形态异常,最常被累及的动脉是椎动脉起始段(14例)和颅内段(13例)及基底动脉(7例);出院时7例患者(20.6%)存在预后不良,其中6例(17.6%)为重度残疾,1例(2.9%)死亡.近中远段同时受累和基底动脉受累的患者表现出预后不良.结论 血管形态异常是多灶性后循环缺血的重要病理基础和致病因素,病灶区段的分布和数目及血管受累部位是决定预后的关键因素.     

Multiple acute infarcts in the posterior circulation.

OBJECTIVE--to evaluate clinical, radiological, and prognostic features of patients with multiple acute infarcts in remote arterial territories of the posterior circulation. DESIGN--Data analysis from a prospective acute stroke registry in a community based primary care centre using a standard protocol including MRI and MRA. RESULTS--In three and a half years, 27 of the 236 patients (11%) with posterior circulation stroke had multiple acute infarcts in the posterior circulation as shown by gadolinium enhancement on MRI. Eighteen patients had multiple infratentorial and supratentorial infarcts including the cerebellum and posterior cerebral artery territory, with coexisting brainstem involvement in seven patients. Fourteen patients had a rostral basilar artery syndrome and cerebellar signs; four patients had a visual field defect with cerebellar signs. Causes were vertebral (six) or basilar (four) artery atheromatosis, and cardioembolism (four). Seven patients had multiple acute infarcts in the posterior circulation of the cerebellum and lower brainstem. Brainstem and cerebellar signs were found in most patients (five); aetiologies were small vessel disease (four), cardioembolism (one), and vertebral artery dissection (one). Two patients with large artery atheromatosis had multiple acute infarcts in the posterior circulation in the brainstem and posterior cerebral artery territory. One month after stroke more than 25% of the patients were dependent or had died. There was no difference in the outcome between the three groups, and recovery was linked to the size of infarcts rather than to a high number of infarcts. CONCLUSIONS--multiple acute infarcts in the posterior circulation usually involve the cerebellum. Simultaneous brainstem and posterior cerebral artery territory infarcts sparing the cerebellum are uncommon. They can be suspected clinically before neuroimaging, mainly when supratentorial and infratentorial infarcts coexist. This may be important, because different patterns of infarction are associated with different causes of stroke.     

Lesion patterns and etiology of ischemia in the anterior inferior cerebellar artery territory involvement: a clinical – diffusion weighted – MRI study

The topography and mechanism of stroke in the anterior inferior cerebellar artery (AICA) territory are delineated before, but the detailed clinical spectrum of lesions involving AICA territory was not studied by diffusion weighted imaging (DWI). We reviewed 1350 patients with posterior circulation ischemic stroke in our registry. We included patients if the diagnosis of AICA territory involvement was confirmed, and DWI, and magnetic resonance angiography were obtained in the 3 days of symptoms onset. The potential feeding arteries of the AICA territory were evaluated on magnetic resonance imaging (MRI) using a three-dimensional rotating cineoangiographic method. There were 23 consecutive patients with lesion involving AICA territory, six with isolated lesion in the AICA territory, six with posterior inferior cerebellar artery, 11 with multiple posterior circulation infarcts (MPCIs). The clinical feature of isolated AICA infarct was vertigo, tinnitus, dysmetria, ataxia, facial weakness, facial sensory deficits, lateral gaze palsy, and sensory-motor deficits in patients with pontine involvement. Patients with largest lesion extending to the anterior and inferolateral cerebellum showed mixed symptomatology of the lateral medullary (Wallenberg's syndrome) and AICA territory involvement. Patients with MPCIs presented various clinical pictures with consciousness disturbances and diverse clinical signs because of involvement of different anatomical structures. Large-artery atherosclerotic disease in the vertebrobasilar system was the main cause of stroke in 12 (52%) patients, cardioembolism (CE) in one (4%), and coexisting large-artery disease and a source of CE in four (17%). The main cause of stroke was atheromatous vertebrobasilar artery disease either in the distal vertebral or proximal basilar artery. The outcome was usually good except those with multiple lesions. The new MRI techniques and clinical correlations allow better definition of the diverse topographical and etiological spectrum of AICA territory involvement and associated infarcts which was previously based on pathological and conventional MRI studies.     

Vertebrobasilar infarcts in patients with dolichoectatic basilar artery

We reported 18 patients who had stroke in the posterior circulation with dolichoectatic basilar artery. TIAs preceded posterior circulation infarct in 5 patients. Strokes involved medulla oblongata (3), pons (4), cerebellum (4), mesencephalon (4), thalamus or occipital lobe (3). Dolichoectatic basilar artery also produced hydrocephalus in one patient. The mechanism of stroke may be due to penetrating artery occlusion, basilar artery thrombosis or an embolism from the abnormal basilar artery. Short-term prognosis was poor seeing that 4 patients died within 12 days of stroke.     

加强对后循环缺血性卒中/短暂性脑缺血发作的认识

后循环缺血性卒中（posterior circulation stroke,PCS）/短暂性脑缺血发作（transient ischemic attack,TIA）占全部卒中及TIA的1/5,其临床表现按血管分布可呈现不同的症状,以头晕最常 见。50%以上椎-基底动脉梗死患者在几天或几周前会出现TIA症状,这些先兆症状可辅助早期识别 PCS。PCS的复发率高于前循环,尤其是伴椎-基底动脉狭窄的患者,可通过完善计算机断层扫描血管 成像（computed tomography angiography,CTA）、磁共振血管成像（magnetic resonance angiography,MRA） 等辅助检查明确血管狭窄程度。另外,对侧支循环建立充分的后循环重度狭窄或闭塞,其神经功能 缺损程度较轻,且预后更好。     

Cerebellar infarction in the territory of the superior cerebellar artery: a clinicopathologic study of 33 cases

We reviewed the clinical and pathologic findings in 33 patients with infarcts in the territory of the superior cerebellar artery (SCA). The clinical manifestations included the rostral basilar artery syndrome (8); coma at onset, often with tetraplegia (11); cerebellar and vestibular signs (9, with delayed coma due to cerebellar swelling in 6); and, in only 1 patient, the "classic" syndrome of the SCA. Clinical features were overshadowed by an infarct in the territory of the middle cerebral artery in 3 other patients, and the diagnosis was made only at autopsy in a fourth. Pathologically, SCA infarcts occurred in isolation in 7 patients. The most striking finding was the high frequency of associated infarcts in the territory of the rostral part of the basilar artery (73%). One-third of patients also had an infarct in the territory of the posterior inferior cerebellar artery, sometimes associated with infarction of the anterior inferior cerebellar artery. Tonsillar herniation was observed in 15 patients, 8 of whom had no infarcts in other cerebellar territories. Occlusions occurred mainly in the distal basilar artery and distal vertebral artery. The infarcts were mostly caused by cardiac and artery-to-artery emboli.     

Juvenile-onset multiple brain infarcts localized in the posterior circulation: a case report]

We report a 37-year-old male patient with multiple brain infarcts due to arterial lesions localized in the posterior circulation, who developed a paramedian pontine infarct on the left side. He had been treated as schizophrenia for 20 years. A cranial CT performed one year before showed old small infarcts in the territories of the bilateral thalamo-perforating and left thalamo-geniculate arteries and the right posterior inferior cerebellar artery. The vertebral and basilar arteries were small in diameter on MRI and MR angiography(MRA). Cerebral angiography revealed a narrow smooth basilar artery. In addition, the P2 segments of the bilateral posterior cerebral arteries were markedly narrow with irregular walls. Carotid arteriograms were normal and no atherosclerosis was found. The nature of these arterial lesions remains unknown in this case. Even if MRA shows vertebrobasilar artery hypoplasia, a known congenital risk factor of a posterior circulation infarct, we must rule out a possibility that some arterial pathology is going on.     

双侧小脑梗死模式的探讨

目的探寻双侧小脑梗死的模式和机制。方法经MRI弥散成像(DWI)证实急性期小脑梗死的患者,根据梗死灶的分布将患者分为单侧小脑梗死组(UCI)和双侧小脑梗死组(BCI),并对两组的人口学特征、血管分布、小脑以外梗死灶以及病因进行了比较。结果因急性卒中入院的115例后循环脑梗死患者中,56例为小脑梗死或小脑合并其它部位梗死,其中单侧小脑梗死36例(64.3%),双侧小脑梗死20例(35.7%)。基线资料比较显示,脑卒中史(P=0.002)、纤维蛋白元水平(P=0.036)和入院时NIHSS评分(P=0.001)在双侧小脑梗死组明显高于单侧小脑梗死组。按血管分布区划分,小脑后下动脉(PICA)供血区小脑梗死发生率最高,且更多发生单侧小脑梗死(P=0.006);而双侧小脑梗死更常见于PICA+小脑上动脉(SCA)供血区(P=0.004)。双侧小脑梗死组合并小脑以外梗死灶的发生率明显高于单侧小脑梗死组(P=0.002),特别是合并幕下梗死灶常见(P=0.022)。在卒中机制上,双侧小脑梗死以大动脉粥样硬化性病变更多见(P=0.041),责任动脉病变主要是在椎动脉V4段、V4段与BA接合处的重度狭窄或闭塞。结论双侧小脑梗死并不少见,常见于PICA+SCA供血区;大动脉粥样硬化所致动脉源性栓塞是其卒中重要机制之一。     

Midbrain infarction: associations and aetiologies in the New England Medical Center Posterior Circulation Registry

Most reports of midbrain infarction have describedclinicoanatomical correlations rather than associations andaetiologies. Thirty nine patients with midbrain infarction (9.4%) aredescribed out of a series of 415 patients with vertebrobasilarischaemic lesions in the New England Medical Center PosteriorCirculation Registry. Patients were categorised according to therostral-caudal extent of infarction. The "proximal" vertebrobasilarterritory includes the medulla and posterior inferior cerebellar artery territory. The "middle" territory includes the pons and anterior inferior cerebellar artery territory. The "distal" territoryincludes the rostral midbrain, thalami, superior cerebellum, and medial temporal and occipital lobes. Midbrain infarction was accompanied by"proximal" territory infarcts in four patients, and by "middle" territory infarction in 19 patients. Thirteen patients had associated "distal" territory infarcts, three of whom had occipital ortemporal lobe infarcts. Only three patients had isolated midbraininfarcts. Cardioembolism (n=11), in situ thrombosis (n=9), large artery to artery embolism (n=7), and intrinsic branch penetrator disease (n=5)were the most common aetiologies. Bilateral infarction and accompanyingpontine infarction were associated with the most extensivevertebrobasilar occlusive disease. Midbrain infarction was 10-fold morelikely to be accompanied by ischaemia of neighbouring structures thanit was to occur in isolation. Recognition of the different patterns ofinfarction may act as a guide to the underlying aetiology and vascular lesions.