Use of stimulation mapping and corticography in the excision of arteriovenous malformations in sensorimotor and language-related neocortex

The excision of an arteriovenous malformation (AVM) located within eloquent neocortex presents a formidable neurosurgical challenge. Compromise of the vascular supply to normal surrounding brain or surgical trauma to essential neighboring neocortex may result in unacceptable postoperative neurological morbidity. In addition, successful removal of these lesions without the benefit of intraoperative corticography may leave in situ areas of highly epileptogenic brain, resulting in continued epilepsy. In this report, we describe eight patients who underwent craniotomy and excision of AVMs at our institutions. Six of these lesions were located in the dominant (left) hemisphere, and two were on the right. All patients underwent preoperative testing with Amytal administered via the carotid artery (Wada test). Subsequently, the patient was placed under local anesthesia, and we performed a craniotomy. Electrocorticography was used to identify epileptogenic brain in the region of the AVM and to establish after-discharge thresholds to electrical stimulation. Stimulation-mapping techniques were then used to delineate critical motor, sensory, and language areas. Trial occlusion of feeding vessels was also carried out to document postocclusion neurological deterioration, if any. At a later time, a second procedure was performed under general anesthesia to excise the lesion and any epileptogenic foci, using the cortical maps derived earlier. Using these techniques, it was possible to effect complete excision of these lesions in seven of eight patients without causing additional neurological deficits.