The prevalence of cerebral arteriovenous malformation (CAVM) in first-degree relatives (FDRs) of patients with a CAVM was increased but did not meet a prespecified criterion for a shared familial risk factor. In combination with the low absolute risk of a CAVM in FDRs, the results do not support screening of FDRs for CAVMs 2).
Because of the rarity of the disease and the existence of asymptomatic patients, establishing a true prevalence rate is not feasible. Owing to variation in the detection rate of asymptomatic AVMs, the most reliable estimate for the occurrence of the disease is the detection rate for symptomatic lesions: 0.94 per 100,000 person-years (95% confidence interval, 0.57-1.30/100,000 person-years). This figure is derived from a single population-based study, but it is supported by a reanalysis of other data sources. The prevalence of detected, active (at risk) AVM disease is unknown, but it can be inferred from incidence data to be lower than 10.3 per 100,000 population. 4).
AVMs account for between 1 and 2% of all strokes, 3% of strokes in young adults, 9% of subarachnoid haemorrhages and, of all primary intracerebral 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 presentations with unprovoked seizures (1%), and of people presenting with headaches in the absence of neurological signs (0.3%). At the time of detection, at least 15% of people affected by AVMs are asymptomatic, about one-fifth present 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 fatality is 1-1.5%, the crude annual risk of first occurrence of haemorrhage from an unruptured AVM is approximately 2%, but the risk of recurrent haemorrhage may be as high as 18% in the first year, with uncertainty about the risk thereafter. For untreated AVMs, the annual risk of developing de novo seizures is 1%. There is a pressing need for large, prospective studies of the frequency and clinical course of AVMs in well-defined, stable populations, taking account of their prognostic heterogeneity 5).
Both sexes are affected equally. AVMs are the leading cause of nontraumatic intracerebral hemorrhage in people less than 35 years old 8).
Most lesions reach attention in patients in their 40's and 75% of the hemorrhagic presentations occur before the age of 50 years 9)
According to autopsy studies, only 12% of AVMs become symptomatic during life 10).
They are the most frequently encountered structural cause of spontaneous intracerebral hemorrhage in childhood, excluding hemorrhages of prematurity.
AVMs are seen more frequently on MRI with advancing age in children and young adults 11).