Middle cerebral artery dissections: differences between isolated and extended dissections of internal carotid artery.

Isolated middle cerebral artery dissection (MCAD) has rarely been encountered clinically and few have reviewed it systemically. The etiologies, clinical manifestations, natural clinical course and prognosis of MCAD remain poorly understood. From 1995 to 2004, there were 5 cases diagnosed clinically and angiographically to have MCAD (isolated MCAD in 1, ICAD-MCAD in 4) from a medical center in Taiwan. MEDLINE (1966-2003) was searched for published articles in English that concerned the diagnosis of MCAD. Clinical presentations, stroke types, angiographic findings, etiologies, treatment strategies and outcomes were compared between cases with isolated MCAD or ICAD-MCAD. There were 23 cases (male, 46%; mean age, 22.9+/-19.5 years) with 24 events of isolated MCAD and 31 cases (male, 47%; mean age, 22.2+/-12.9 years) with 35 events of ICAD-MCAD. The types of stroke in isolated MCAD group included subarachnoid hemorrhage (12%) and cerebral infarction (88%); and in ICAD-MCAD group were subarachnoid hemorrhage (6%) and cerebral infarction (94%). The presenting symptoms were similar between both groups. Fluctuating course was more often in isolated MCAD than in ICAD-MCAD (17% vs. 3%, p=0.061). Recurrence of dissection events in both groups was infrequent (4% vs. 9%, p=0.56). Both groups had high case-fatality rates (MCAD, 48%; ICAD-MCAD, 58%). The cause of dissection in both groups was idiopathic in the majority. Congenital vessel wall defects were found in 26% of ICAD-MCAD, but in only 4% of isolated MCAD (p=0.066). In contrast, preceded trauma was more often found in isolated MCAD than ICAD-MCAD (35% vs. 19%, p=0.085). Arteritis was noted in 16% of ICAD-MCAD patients, but none in isolated MCAD. Angiography revealed segmental stenosis in 72% of isolated MCAD and 96% of ICAD-MCAD. Aneurysmal dilatation of the involved cerebral arteries was noted in 28% of isolated MCAD, but none in MCAD-ICAD. Both isolated MCAD and ICAD-MCAD can cause vascular events with high mortality rates. Several aspects differed between 2 groups, including clinical course, underlying etiologies and angiographic findings.