Clinical significance of preoperative fiber-tracking to preserve the affected pyramidal tracts during the resection of brain tumors in patients with preoperative motor weakness

¹ Kyoto University Graduate School of Medicine, Japan
² Kyoto University Graduate School of Medicine

^* To whom correspondence should be addressed. E-mail: mikunin{at}kuhp.kyoto-u.ac.jp.

Accepted 7 February 2007

	Abstract

Objective: To clarify the clinical usefulness of preoperative fiber tracking in affected pyramidal tracts for intraoperative monitoring during the removal of brain tumors from patients with motor weakness.

Methods: We operated on ten patients with mild to moderate motor weakness due to brain tumors located near the pyramidal tracts under local anesthesia. Before surgery, we performed fiber-tracking imaging of the pyramidal tracts, then transferred this information to the neuronavigation system. During removal of the tumor, motor function was evaluated with motor evoked potential elicited by cortical/subcortical electrical stimulation and with voluntary movement.

Results: In eight patients, the locations of the pyramidal tracts were estimated preoperatively by fiber tracking; motor evoked potentials were elicited on the motor cortex and subcortex close to the predicted pyramidal tracts. In the remaining two patients, in which fiber tracking of the pyramidal tracts revealed their disruption surrounding the tumor, cortical/subcortical electrical stimulation did not elicit responses clinically sufficient to monitor motor function. In all cases, voluntary movement with mild to moderate motor weakness was extensively evaluated during surgery and was successfully preserved postoperatively with appropriate tumor resection.

Conclusions: Preoperative fiber tracking could predict the clinical usefulness of intraoperative electrical stimulation of the motor cortex and subcortical fibers (i.e., pyramidal tracts) to preserve affected motor function during brain tumor removal. In patients for whom fiber tracking failed preoperatively, awake surgery is more appropriate to evaluate and preserve moderately impaired muscle strength.

Keywords: MEP, awake surgery, fiber tracking, motor weakness, pyramidal tract