Prognostic value of magnetic resonance imaging combined with electromyography in the surgical management of cervical spondylotic myelopathy

Abstract

The present study aimed to evaluate the value of pre-operative magnetic resonance imaging (MRI) combined with electromyography (EMG) for predicting clinical outcome following surgical management of cervical spondylotic myelopathy (CSM). A total of 94 patients with cervical compressive myelopathy were prospectively enrolled and treated with anterior, posterior and posterior-anterior united decompression between October 2007 and February 2009. Prior to surgery 1.5-T MRI and EMG were performed in all patients. The patients were classified into four types based on the presence (+) or absence (-) of an increased signal intensity (ISI) on the T2-weighted magnetic resonance (MR) images and also based on the positive (+)/negative (-) results of the EMG. The four types were as follows: Type I, MRI/EMG (-/-); Type II, MRI/EMG (+/-); Type III, MRI/EMG (-/+); and Type IV, MRI/EMG (+/+). The clinical outcome was also graded according to a modified Japanese Orthopedic Association (JOA) scoring system. Furthermore, pre- and post-operative clinical data were statistically analyzed to explore the correlation between the factors. There were 36 cases (38%) of Type I, 16 (17%) of Type II, 13 (14%) of Type III and 29 (31%) of Type IV. According to the analysis of the clinical data between the four types, there were significant differences in the disability classifications, pre-operative JOA scores and disease duration (P<0.05), but there were no significant differences in gender, age or cord compression ratios (P>0.05). Until the final follow-up, there was a significant difference in the recovery ratio between the four study groups (Hc=27.46, P<0.05). Further comparison showed that the surgical outcome was best in Type I patients and worst in Type IV patients. In conclusion, there was a distinct correlation between classification and the rate of clinical improvement. Patients who had a negative EMG and those without an ISI on T2-weight images tended to suffer only mild symptoms, a short disease duration and, most significantly, experience a good surgical outcome.

Keywords: cervical spondylotic myelopathy; electromyography; magnetic resonance imaging; prognosis.