Prognosis

Mortality associated with arteriovenous malformation (AVM) hemorrhage is lower than expected from aneurysmal rupture or from intracerebral hemorrhage unrelated to brain AVM rupture.[42][92] Mortalities of up to 18% have been reported following AVM rupture.[1][2]

Risk of hemorrhage

Given that there is no consensus regarding the risk factors for AVM rupture, let alone their relative contribution, it is extremely difficult to predict the risk of conservative management. The overall annual hemorrhage risk of 2% to 4% is used. The risk is increased during the first 5 years following hemorrhage and is highest in the first year, when rates of >30% have been reported.[34][35] However, hemorrhage risk seems to be overestimated in patients without hemorrhagic presentation, with rates of <1% per year.[22] In these patients the risks of treatment may outweigh the risk of rupture.[36] 

One multicenter study reported a significantly lower risk of death or stroke among patients with unruptured brain AVM who were randomized to medical management than those randomized to neurosurgery, embolization, or stereotactic radiosurgery, alone or in combination (hazard ratio 0.27, 95% confidence interval 0.14 to 0.54).[84] Outcome data were available for 223 patients with a mean follow-up of 33.3 months when the trial was stopped by the National Institute of Neurological Disorders and Stroke-appointed data and safety monitoring board. The composite endpoint of death or symptomatic stroke was reached in 10.1% of patients in the medical arm versus 30.7% of patients in the interventional arm.[84] A subsequent analysis of the 5-year follow up data showed that these differences in the composite endpoint persisted.​[85]​

Proponents of the trial results argue for medical management of all unruptured AVMs. Critics point to a probable selection bias prior to randomization, with a large number of eligible patients not enrolled, and therefore a lack of generalizability of the trial results.

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