BACKGROUND: Microsurgical resection of arteriovenous malformations (AVMs) located in the language and motor cortex is associated with the risk of neurological deterioration, yet electrocortical stimulation mapping has not been widely used.
OBJECTIVE: To demonstrate the usefulness of intraoperative mapping with language/motor AVMs.
METHODS: During an 11-year period, mapping was used in 12 of 431 patients (2.8%) undergoing AVM resection (5 patients with language and 7 patients with motor AVMs). Language mapping was performed under awake anesthesia and motor mapping under general anesthesia.
RESULTS: Identification of a functional cortex enabled its preservation in 11 patients (92%), guided dissection through overlying sulci down to the nidus in 3 patients (25%), and influenced the extent of resection in 4 patients (33%). Eight patients (67%) had complete resections. Four patients (33%) had incomplete resections, with circumferentially dissected and subtotally disconnected AVMs left in situ, attached to areas of eloquence and with preserved venous drainage. All were subsequently treated with radiosurgery. At follow-up, 6 patients recovered completely, 3 patients were neurologically improved, and 3 patients had new neurological deficits.
CONCLUSION: Indications for intraoperative mapping include preoperative functional imaging that identifies the language/motor cortex adjacent to the AVM; larger AVMs with higher Spetzler-Martin grades; and patients presenting with unruptured AVMs without deficits. Mapping identified the functional cortex, promoted careful tissue handling, and preserved function. Mapping may guide dissection to AVMs beneath the cortical surface, and it may impact the decision to resect the AVM completely. More conservative, subtotal circumdissections followed by radiosurgery may be an alternative to observation or radiosurgery alone in patients with larger language/motor cortex AVMs.