Trapezius motor evoked potential in evaluations of corticospinal tract lesions

Abstract

We wanted to know whether trapezius motor evoked potentials (MEPs) are helpful in the evaluation of corticospinal (CS) lesions above the fifth cervical segment (C5) and compared trapezius MEP measurements in patients with and without radiological evidence of CS lesions. Trapezius MEPs were routinely recorded in all MEP studies performed in our hospital. Patients who had MEP studies as well as brain and cervical spine imaging were retrospectively assigned to two groups. Group 1 had radiological evidence of CS lesion above the level of C5 whilst group 2 did not. Forty-nine patients were included in the study. Twenty-eight patients were assigned to group 1 and 21 patients to group 2. The frequencies of abnormal values in the two groups were compared. Twelve (43%) patients in group 1 and three (14%) in group 2 had prolonged MEP latencies. Thirteen patients in group 1 had indentation or impingement of the cervical cord by intervertebral discs as the only relevant radiological abnormality. Seven (54%) of these patients were found to have prolonged trapezius MEP latencies, providing functional correlates to the radiological abnormalities. Our study gives evidence to the usefulness of trapezius MEP study in the evaluation of CS lesions.