Preoperative functional mapping for rolandic brain tumor surgery

The resection of tumors within or close to eloquent motor areas is usually guided by the compromise between the maximal allowed resection and preservation of neurological functions. Navigated transcranial magnetic stimulation (nTMS) is an emerging technology that can be used for preoperative mapping of the motor cortex. We performed pre-surgical mapping by using nTMS in 17 patients with lesions in or close to the precentral gyrus. The study was conducted on consecutive patients scheduled for surgical treatment. nTMS allowed to exactly localize the motor cortex in 88.2% of cases. In 70.6% it provided the surgeon with new unexpected information about functional anatomy of the motor area, influencing the pre-operative planning. Moreover, in 29.4% these functional information had a clear impact on surgery, making necessary a change of surgical strategy to avoid damage to the motor cortex. Our results prove that nTMS has a large benefit in the treatment of rolandic brain tumors. It adds important information about spatial relationship between functional motor cortex and the tumor and reduces surgical-related post-operative motor deficits.