Abstract
Twenty-two brain tumor operations were performed utilizing cortical mapping under local anesthesia for 18 patients. The tumors were situated in motor area in 16 patients and the speech area in 2 patients. The histological diagnoses were metastasis (13 cases), glioma (4 cases), and hemangioma (1 case). Before operation, acupuncture needles were inserted in 5 sites; zanzhu (B2), fengchi (G20), hegu (L14), quanliao (S18), and yuyao (Extra 5). The patient's head was fixed with a Mayfield head rest in the operating room. Craniotomy was performed under local anesthesia which was maintained throughout the operation. After opening the dura mater, the cortical surface was stimulated with a silver tipped bipolar electrode to identify the eloquent area. The threshold for evoking muscle contraction was 2-3 mA at 50 Hz. After dissection through the electrically silent cortex, monoparesis appeared in the very last stage in 4 of 17 operations. Dissection causing patients to complain of paresthesia at first, followed by motor responses at a higher threshold resulted in postoperative deficit in 2 of 2 operations. Dissection stopped at the electrically responsive area caused no deficit in 2 operations. Cortical stimulation for 2 tumors in the speech cortex caused no speech arrest. No deficit resulted after the operation. For example, a 52-year-old female presented with progressive left hemiparesis. The diagnosis was a metastatic tumor in the right posterior frontal lobe. Cortical mapping elicited a motor response along the edge of the posterior border of the tumor. Her hemiparesis gradually improved after the tumor removal. A 25-year-old male had bilateral metastatic tumors around the motor cortex. The tumor on the right was successfully removed. At the second operation, cortical mapping by our method was performed. The cortex just above the tumor responded to the stimulation. An Initial sensory response was followed by motor response at a higher threshold, so we thought that the tumor was situated in the sensory cortex. Postoperatively, weakness and numbness of the right hand appeared. Intraoperative cortical mapping is generally performed under general anesthesia. Only speech testing is performed with the patient awake. Continuous stimulation of motor cortex and motor evoked potential monitoring provides useful information, but in our method, the complaints expressed directly by the awake patients provided a simple and precise monitoring. Patients will feel no discomfort if recently developed short-acting intravenous anesthetics are used during opening or closing of the wound.
