Purpose: To investigate factors predisposing to spontaneous hemorrhage in the early period after embolization of brain arteriovenous malformations (AVMs).
Methods: The authors report 15 cases of spontaneous hemorrhage in a consecutive series of 492 brain AVMs totally or partially treated with intranidal injections of a polymerizing mixture, from 1984 to June 1998. Retrospective analysis of the records was performed with special attention to the angio-architectural features before embolization, details of embolization procedures and induced angiographic modifications.
Results: Pre-embolization features of greater incidence were the presence of steal phenomena (87%), multiple feeding arteries (100%), a compact aspect of the nidus (93%), and lobar topography (87%). In most cases the volume of injected glue exceeded 1 ml (80%), venous embolization was significant (67%) and immediate angiographic control showed venous stagnation in and/or around the nidus (80%). Four patients were asymptomatic (incidental discovery on systematic CT at day 3). Among the remaining 11 symptomatic patients, 6 were operated to evacuate an intracerebral hematoma, outcome was good for 4, 5 were left with sequelae and 2 died.
Conclusion: Spontaneous hemorrhagic complications affected 3.04% of embolized patients. The combination of certain angio-architectural features, significant venous embolization and persistent venous stagnation within the nidus seem to have some predictive value of high risk hemorrhage. In light of this, additional preventive measures must be taken and a neurosurgical team systematically kept on standby.