[The usefulness of electromyographical monitoring with intraoperative brain mapping during motor lesionectomy]

Surgery for resection of supratentorial lesions near the motor areas and/or internal capsule carries an associated risk of damage to cortical or subcortical motor pathways. Intraoperative brain mapping, using direct cortical electric stimulation, is a surgical adjunct used during lesionectomy in functional cortex. The technique of observing movements elicited by electrical stimulation has proved useful for intraoperative localization of motor pathways but it is difficult observe the entire body at once. Thus, a small movement may be missed while attention is focused on another site.

To determinate the usefulness of electromyographical monitoring in locating motor pathways during neurosurgery in functional cortex.

We recorded multichannel electromyography activity during cortical and subcortical electric stimulation in a consecutive series of 40 patients undergoing craniotomies for lesionectomy near motor cortex or subcortical motor tracts. Because the aim of the electromyography recordings was to sample as many muscles as possible, the two electrodes connected to each different amplifier input were placed in different muscles in the same region of the body.

No motor responses were detected by either electromyographical monitoring or visual inspection in 20% patients. Electromyographical activity was the only indication of motor response in 17%. Motor responses were detected simultaneously by either electromyographical monitoring and visual inspection in 76%.

Electromyography monitoring enhances the ability to detect the location of primary motor cortex and subcortical pathways with electrical stimulation during neurosurgery.