Intra-operative detection of motor pathways using a simple electrode provides safe brain tumor surgery.

Preservation of motor function is very important in patients who require resection of tumors adjacent to the primary motor cortex and pyramidal tract. Resection of tumors in the white matter adjacent to motor cortices routinely requires electrical stimulation of the tumor cavity. However, efforts to detect the pyramidal tract often result in postoperative neurological deterioration. To overcome this problem, a novel bipolar needle electrode was developed which enabled the identification of motor pathways by inserting it into the white matter. Motor-evoked potentials were induced by electrical stimulation with this electrode when it was inserted toward the estimated motor pathway from the resected tumor cavity. The scale on the needle indicated the approximate distance from the tumor cavity wall to the pyramidal tract. We conclude that the motor pathways can be preserved by detecting them neurophysiologically before they are destroyed by tumor resection.