Transcranial MEPs predict clinical outcome during minimally invasive dorsal decompression for cervical spondylotic myelopathy.

Objectives: Motor evoked potential (MEP) monitoring is a reliable method for real-time assessment of corticospinal tract integrity. However, the potential benefits of MEP monitoring during degenerative spine surgery remain controversial. This study aims to determine the role of MEP monitoring during surgery for cervical spondylotic myelopathy (CSM) in prediction of prognosis.

Methods: Transcranial electrical stimulation was performed to elicit MEPs during dorsal decompression for the treatment of CSM. MEP-threshold levels were assessed separately at the beginning and end of the surgery in upper extremity muscles corresponding to nerve roots at the level of/distal to the decompression site. Clinical outcome was measured using the modified Japanese Orthopedic Association score (mJOA).

Results: The study included 47 patients. 31 patients (66 %) showed improvements in neurological function at discharge. A measurable improvement in the majority of tested muscles, or in at least one muscle group, in a given patient highly correlated with mJOA score increase at discharge (p < 0.001) with an odds ratio of 10.3 (CI:2.6-34.4) and 11.4 (CI:2.8-41.3), respectively. Conversely, MEP deterioration was not associated with worse clinical outcome, nor was it predictive of failure to recover.

Conclusion: MEP improvement during CSM surgery seems to be highly predictive of early postoperative neurological recovery and could indicate subclinically enhanced signal conduction. This highlights the potential of MEP monitoring as an intraoperative, real-time predictive tool for clinical recovery after decompression in patients with CSM.