Ahead of Print: Low Threshold Mapping Motor Cortex

Background: Microsurgery within eloquent cortex is a controversial approach due to the high-risk of permanent neurological deficit. Few data exist showing the relationship between mapping stimulation intensity required for eliciting a muscle motor evoked potential (MEP) and distance to the motor neurons; furthermore, the motor threshold at which no deficit occurs remains to be defined.

Objective: To evaluate the safety of low threshold MEP mapping for tumor resection close to the primary motor cortex.

Methods: Fourteen patients undergoing tumor surgery were included. Motor threshold was defined as the stimulation intensity that elicited MEPs from target muscles (amplitude >30[mu]V). Monopolar high-frequency motor mapping with train-of-five stimuli (HF-TOF) (pulse duration=500[mu]s; interstimulus interval=4.0ms; frequency=250Hz) was used to determine motor response negative sites where incision and dissection could be performed. At sites negative to 3mA HF-TOF stimulation, the tumor was resected.