[Surgical management for preserving motor function in patients with gliomas near the primary motor cortex: usefulness of preoperative identification of motor cortex and intraoperative monitoring of motor evoked potentials].

Preoperative identification of precentral gyrus and intraoperative monitoring of motor evoked potentials (MEPs) were performed to preserve postoperative motor function in seven patients with gliomas near the primary motor cortex. Tumors were astrocytomas in 3 patients, glioblastomas in 2 patients, anaplastic astrocytoma and mixed glioma in one patient each. Preoperative identification of the primary motor cortex was performed by three-dimensional (3D) display of magnetic resonance (MR) images and by functional images using MR imaging and single-photon emission tomography. The primary motor cortex identified by 3D display of MR images coincided well with that identified by functional images. 3D display of MR images was also useful for detecting the relationship between the tumor and the primary motor cortex. Intraoperatively, the central sulcus was confirmed by the finding of phase reversal of cortical somatosensory evoked potential, and this corresponded with the preoperative identifications by 3D display and by functional mapping. The primary motor cortex was stimulated electrically, and MEP (corticospinal evoked potential) was continuously monitored during surgery using electrodes inserted in the cervical epidural space. The amplitude of direct waves of MEPs during surgery was maintained above half of that recorded at the beginning of tumor removal, and all patients showed preservation of preoperative motor function. These results suggest that preoperative identification of precentral gyrus and intraoperative MEP monitoring provide useful information for preserving motor function in patients with gliomas near the primary motor cortex.