The lesion was carefully explored to differentiate feeding vessels from normal cortical branches (feeding branch of middle cerebral artery coming from the right in the microscopic view). Once landmarks had been established, the lesion was carefully unroofed.
The surgical approach to AVMs is to divide arterial feeders first, leaving venous drainage intact to allow decompression of the lesion until the last moment. Closing venous drainage is extremely hazardous because the increased pressure in the lesion during manipulation can lead to catastrophic bleeding. The first arterial branch to the lesion (arrow) has been cauterized and divided.
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