OBJECTIVEA series of 22 patients with arteriovenous malformations (AVMs) were surgically treated using computer-assisted image guidance. The value of image guidance for nidus definition and detection of feeding arteries and draining veins was assessed.METHODSSeven of the 22 patients presented with hemorrhage. The sizes of the AVMs ranged from 1 to 8 cm. Six patients underwent preoperative embolization. For 18 patients (81.8%), the AVMs were located in highly eloquent areas. A passive-marker-based neuronavigation system (BrainLab, Heimstetten, Germany) was used for intraoperative image guidance. Segmentation of the pathological vessels was performed preoperatively, on the basis of 2-mm helical computed tomographic angiographic slices, to obtain three-dimensional reconstructions of the AVMs. Temporary clips were initially placed on all identifiable feeding arteries, for intranidal pressure reduction before AVM dissection. Dissection of the AVMs was then performed along the main draining veins, as identified by neuronavigation. Patient follow-up monitoring ranged from 3 to 16 months (median, 7 mo).RESULTSThe computer-calculated registration accuracy ranged between 1.1 and 3.1 mm (median, 1.4 mm). Exact nidus definition was possible for all 22 patients. The principal draining veins were also identified for all patients. Feeding arteries could be detected after the segmentation process when the vessels were at least 3 mm in diameter (19 patients). Complete collapse of the AVMs was achieved with initial clip application for 3 patients; partial intranidal pressure reduction was observed for 12 patients. No significant decompression by feeder clipping was possible for pre-embolized AVMs. Perioperative mortality and morbidity rates were 0 and 14%, respectively.CONCLUSIONThis image-guided technology allows observation of the relationship between AVMs and adjacent brain structures, increasing spatial orientation during surgery. Definition of an optimal surgical approach and early localization of feeding arteries for temporary occlusion minimize tissue manipulation and enhance the safety of direct dissection along the draining veins, which is necessary in eloquent areas.