A Longer Duration of Myelopathy Symptoms is Associated With the Lack of Intraoperative Motor Evoked Potential Improvement During Decompressive Cervical Myelopathy Surgery

Abstract

Study design: Retrospective cohort study.

Objective: We aim to investigate the relationship between the intraoperative motor evoked potential (MEP) signal changes during surgical treatment of cervical myelopathy with postoperative functional outcomes and determine what factors correlate with MEP signal changes.

Summary of background data: Intraoperative neurophysiologic monitoring with MEP for cervical cord decompression can potentially predict postoperative neurological complications.

Materials and methods: We prospectively collected data from 114 consecutive cervical compressive myelopathy patients who underwent decompressive cervical spine surgery. Functional outcomes were measured preoperatively and postoperatively at the 6-month mark, using the modified Japanese Orthopedic Association score.

Results: Among the 114 patients, 87 patients showed significant MEP improvement, 1 patient with MEP degeneration, 3 patients with no change in MEP, and 23 patients with MEP change, but which eventually returned to baseline. Univariate analysis showed that patients with MEP improvement had similar 6-month functional and Japanese Orthopedic Association scores compared with patients who did not have MEP improvement. Critically, a longer duration of symptoms was shown to have a statistically significant relationship with patients who did not have MEP improvement on univariate analysis (49.2 wk in patients with no MEP improvement compared with 34.59 wk in patients with MEP improvement, P = 0.03) but this did not translate to differences in functional outcomes. There was also no statistically significant association between the functional outcome scores and demographics, surgical, or radiologic factors.

Conclusions: Our study shows that the duration of symptoms is not attributed to lower functional outcomes but is associated with a lack of MEP improvement.

Level of evidence: Level III.