Value of somatosensory evoked potentials in diagnosis, surgical monitoring and prognosis of cervical spondylotic myelopathy

Abstract

Background: The value of somatosensory evoked potentials (SEPs) in the diagnosis and prognosis of cervical spondylotic myelopathy, as well as the usefulness of monitoring intraoperative potentials in terms of safety and predictive factors were investigated. Methods: Each of the 76 myelopathic patients underwent surgical intervention. According to the wave configurations of the SEPs, the cases were categorised into four groups: Type I, II, III and IV. The clinical myelopathy disability was classified and the severity of neurological deficits was scored. Clinical function after surgery was evaluated. Preoperative potentials and intraoperative monitoring were categorized. The correlations between evoked potentials detection, monitoring, myelopathy disability and surgical outcome in the different groups were discussed. Results: According to the configurations of the SEPs, there were 27 patients (36%) of Type I, 30 patients (39%) of Type II, 8 patients (11%) of Type III, and 11 patients (14%) of Type IV. The categorised evoked potentials were shown to be significantly associated with the clinical representation of myelopathy (P <0.01) and the recovery rate from identifiable SEPs waves (groups A, B and C) was significantly higher than unidentifiable waves (group D, P <0.01). A deterioration of SEPs was detected in 23 cases (30%), whereas there was no change in 40 cases (53%) and improvements in 13 cases (17%). A significant difference in recovery rates could be observed in various monitoring groups within the short-term follow-up period, while there were no obvious differences in the long-term follow-up groups. Conclusions: SEP technique is a valuable and practical tool for the diagnosis, monitoring and prognosis of myelopathy. Classified evoked potentials are well correlated with cervical spondylotic myelopathy disability, and unidentifiable SEPs waves in patients are indicative of a relatively poor outcome. In addition, intraoperative monitoring of SEPs plays an important role in protecting neural structures during cervical spine surgery.