Functional brain mapping-assisted resection of gliomas in the dominant hemisphere

Localization of the eloquent areas of the brain is very important to maximize the resection of the glioma and minimize the morbidity. Electrical cortical stimulation using subdural electrodes to identify the sensorimotor cortex and language areas was performed in seven patients with glioma at the dominant hemisphere. All the patients received craniotomy to implant subdural electrodes during the first operation. Functional brain mapping was done after the operation, and the sensorimotor cortex and language areas were identified in every patient. After functional brain mapping, these patients received second operation to excise the tumors with a total of four total and three subtotal excisions. In addition to the tumor excision, two patients with intractable seizure received excision of the epileptic foci under electrocorticographic monitoring. After operation, one patient had transient hemiparesis, then recovered completely 12 hours after occurrence. This patient also had slow initiation of speech postoperatively, which disappeared one year after operation. In another patient, the preoperative right hemiparesis had no changes, and her sensory and speech functions were intact after operation. The other five patients had no sensorimotor or speech deficits after operation. After 1 to 4 years and 3 months (mean, 2 years and 8 months) of follow-up, all the patients had good neurological functions except that the patient with right hemiparesis had tumor recurrence 20 months after excision. This patient received tumor resection again and died 2 months after the second resection. The two patients with intractable seizures were free of seizure. From this study, we found functional brain mapping using electrical cortical stimulation accurately localized the sensory areas of the cortex, and the mapping was helpful for maximizing the resection of glioma and minimizing the morbidity.