A systematic review of the frequency and prognosis of arteriovenous malformations of the brain in adults

By systematically reviewing the literature, we have found that there is ver y little information about the frequency and clinical course of arterioveno us malformations (AVMs) of the brain in adults because the methods of most studies have been flawed, and AVMs tend to be treated once they are discove red. The incidence of AVMs is similar to1 per 100 000 per year in unselecte d populations, and the point prevalence in adults is similar to 18 per 100 000. AVMs account for between 1 and 2% of all strokes, 3% of strokes in you ng adults, 9% of subarachnoid haemorrhages and, of all primary intracerebra l haemorrhages, they are responsible for 4% overall, but for as much as one -third in young adults. AVMs are far less common causes of first presentati ons with unprovoked seizures (1%), and of people presenting with headaches in the absence of neurological signs (0.3%). At the time of detection, at l east 15% of people affected by AVMs are asymptomatic, about one-fifth prese nt with seizures and for approximately two-thirds of them the dominant mode of presentation is with intracranial haemorrhage. The limited high quality data available on prognosis suggest that long-term crude annual case fatal ity is 1-1.5%, the crude annual risk of first occurrence of haemorrhage fro m an unruptured AVM is similar to2%, but the risk of recurrent haemorrhage may be as high as 18% in the first year, with uncertainty about the risk th ereafter. For untreated AVMs, the annual risk of developing de novo seizure s is 1%. There is a pressing need for large, prospective studies of the fre quency and clinical course of AVMs in well-defined, stable populations, tak ing account of their prognostic heterogeneity.