Intraoperative Spinal Cord Monitoring of C5 Palsy After Cervical Laminoplasty

Study Design: Retrospective study of C5 palsy after laminoplasty for cervical myelopathy. Objective: The objectives of this study were to investigate the morphologic characteristic of C5 palsy patients undergoing cervical laminoplasty with the intraoperative motor-evoked potential (MEP). Summary of Background Data: A study reported prophylactic foraminotomy for C5 paralysis after laminoplasty for cervical myelopathy. However, no indications have been established. There have been few reports on the intraoperative monitoring of the C5 palsy. This palsy is reported to happen a few days after the surgery in many cases, and the possibility of its detection by intraoperative spinal cord monitoring is unclear. Methods: Of 153 patients with cervical myelopathy, 9 showed a decrease in upper muscle strength by 1 grade or more by postoperative manual muscle test. Of the 9 patients, 4 patients underwent segmental monitoring of upper limbs by MEP and were included in the paralysis group. Of the 153 patients, 74 (444 muscles) in whom both preoperative and postoperative manual muscle test of the upper limbs showed grade 5, and in whom the MEP monitoring of all these muscles was performed, were included in the nonparalysis group. We investigated the presence of intraoperative changes in 4 MEP parameters: amplitude, latency, duration, and waveform pattern, and the presence of foraminal stenosis in the cross-sectional view of preoperative myelographic computed tomography. Results: In the paralysis group (9 muscles) and nonparalysis group (444 muscles), delay in latency was not observed in any muscle (0% and 0%), and 50% or more reduction of amplitude in 1 muscle (11%) and 22 (5%), prolongation of duration in 1 (11%) and 6 (1%), changes of waveform pattern in 3 (33%) and 40 (9%), and foraminal stenosis in 5 (56%) and 80 (18%), respectively. Conclusions: In the paralysis group, the incidences of waveform pattern change on intraoperative MEP and stenosis of the intervertebral foramen were higher than those in the nonparalysis group.