Postoperative segmental C5 palsy after cervical laminoplasty may occur without intraoperative nerve injury: a prospective study with transcranial electric motor-evoked potentials.

STUDY DESIGN: Intraoperative neurophysiologic monitoring with transcranial electric motor-evoked potentials was performed on patients who underwent cervical laminoplasty at a university hospital in a prospective study.

OBJECTIVE: To evaluate the usefulness of intraoperative spinal cord monitoring with transcranial electric motor-evoked potentials for prediction of the occurrence of segmental motor paralysis after cervical laminoplasty.

SUMMARY OF BACKGROUND DATA: Segmental motor paralysis occasionally occurs among patients who undergo expansive laminoplasty for cervical myelopathy, and it has been attributed to nerve root lesions caused by either a traumatic surgical technique or a tethering effect after decompression.

METHODS: Sixty-two consecutive patients (47 men and 15 women; mean age 64 years [range 32-89]) who were scheduled to undergo cervical laminoplasty under intraoperative spinal cord monitoring with transcranial electric motor-evoked potentials were included in this study. Transcranial electrical stimulations were delivered through pin-type electrodes, and the evoked potentials were recorded over the deltoid, biceps, and triceps muscles in the bilateral upper extremities and thoracic spinal cord.

RESULTS: Intraoperative evoked potentials were successfully recorded in all muscles in 57 patients (92%), and incomplete evoked potentials were recorded in the remaining 5 patients. No critical decrease in the amplitude of the evoked potentials was observed in any of the 62 patients. All patients showed sufficient postoperative recovery from their clinical symptoms; however, postoperative transient C5 palsy occurred in 3 patients.

CONCLUSIONS: No abnormalities were observed on transcranial electric motor-evoked potential monitoring, even in those patients who developed postoperative transient C5 palsy. These results suggest that the development of postoperative C5 palsy after cervical laminoplasty is not associated with intraoperative injury of the nerve root or the spinal cord, although the precise mechanism of its development is still unclear. Surgeons should be aware that C5 palsy is a possible complication of cervical laminoplasty, even in the absence of intraoperative nerve injury.