A new criterion for detection of radiculopathy based on motor evoked potentials and intraoperative nerve root monitoring.

OBJECTIVE: Our objective is to use the area of the motor evoked potential (MEP) as a diagnostic tool for intraoperative radicular injury.

METHODS: We analyzed the intraoperative neurophysiological monitoring data and clinical outcomes of 203 patients treated for dorsolumbar spine deformity. The decrease in amplitude was compared with the reduction in the MEP area.

RESULTS: In 11 cases, new intraoperative injuries occurred, nine of them were lumbar radiculopathies. Our new criteria, a decrease MEP area of 70%, yielded a sensitivity and specificity of 1, since it detected all the radicular injuries, with no false positive cases. Using a 70% amplitude decrease criteria, we obtained a sensitivity of 0,89 and a specificity of 0,99. A lower threshold (65% amplitude reduction) yielded a higher number of false positives, whereas a higher threshold (75 and 80%) gave rise to a higher number of false negatives.

CONCLUSIONS: The measurement of the MEP area gave evidence to be more reliable and accurate than the measurement of the amplitude reduction in order to assess and detect intraoperative radicular injuries.

SIGNIFICANCE: The criterion of decrease of the MEP area has a higher reliability and accuracy in the detection of intraoperative radicular lesions than the amplitude reduction.