Predictability of surgical results of herniated disc-induced cervical myelopathy based on spinal cord motor conduction study.

A motor evoked potential (MEP) study with percutaneous magnetic stimulation over the motor cortices and an F-wave study in peripheral nerves were performed to measure spinal cord motor conduction velocity (SCMCV) in 25 patients with herniated disc-induced cervical myelopathy (HDICM). Grading of motor function and assessment of SCMCV were performed before and 2 years after microsurgical discectomy. The results show that functional motor improvement accompanied by an increase in SCMCV occurred in grade I patients with mild neurological impairment after surgery, whereas no definite change was seen in grade II and grade III patients with moderate and severely neurological impairment. This finding suggests that measurement of SCMCV by MEP study with a noninvasive method may provide an objective and quantitative method to assessment of the functional integrity of the spinal motor pathway and that the results of such studies may serve as a predictor in evaluation of surgical outcome in patients with HDICM.