Evaluation of corticospinal excitability in cervical myelopathy, before and after surgery, with transcranial magnetic stimulation: a pilot study

Purpose A pilot study to examine the impact of cervical myelopathy on corticospinal excitability, using transcranial magnetic stimulation, and to investigate whether motor evoked potential (MEP) and silent period (SP) recruitment curve (RC) parameters can detect changes in corticospinal function pre- and post-surgery. Methods We studied six cervical myelopathy patients undergoing surgery and six healthy controls. Clinical and functional scores and neurophysiological parameters were examined prior to and 3 months following the surgery. Results MEP latencies for abductor pollicis brevis (APB) and tibialis anterior (TA) muscles and central motor conduction time were prolonged pre- and post-surgery; SP durations were differentially altered. There were significant differences in parameters of RCs for (1) MEP area in APB (max values, S 50) and TA (slope) between controls and patients pre- and post-surgery and (2) SP duration in APB (max values) between patients pre-surgery and controls. Conclusions The findings of this pilot study suggest an uncoupling of excitatory and inhibitory pathways, which persists at 3 months following cord decompression. RCs for MEP and SP at 3 months provide more information on the functional status of the cord and prompts for a longer term follow-up.