Degenerative Cervical Myelopathy: How to Identify the Best Responders to Surgery?

Abstract

Surgery is the only definitive treatment for degenerative cervical myelopathy (DCM), however, the degree of neurological recovery is often unpredictable. Here, we assess the utility of a multidimensional diagnostic approach, consisting of clinical, neurophysiological, and radiological parameters, to identify patients likely to benefit most from surgery. Thirty-six consecutive patients were prospectively analyzed using the modified Japanese Orthopedic Association (mJOA) score, MEPs/SSEPs and advance and conventional MRI parameters, at baseline, and 3- and 12-month postoperatively. Patients were subdivided into "normal" and "best" responders (<50%, ≥50% improvement in mJOA), and correlation between Diffusion Tensor Imaging (DTI) parameters, mJOA, and MEP/SSEP latencies were examined. Twenty patients were "best" responders and 16 were "normal responders", but there were no statistical differences in age, T2 hyperintensity, and midsagittal diameter between them. There was a significant inverse correlation between the MEPs central conduction time and mJOA in the preoperative period (p = 0.0004), and a positive correlation between fractional anisotropy (FA) and mJOA during all the phases of the study, and statistically significant at 1-year (r = 0.66, p = 0.0005). FA was significantly higher amongst "best responders" compared to "normal responders" preoperatively and at 1-year (p = 0.02 and p = 0.009). A preoperative FA > 0.55 was predictor of a better postoperative outcome. Overall, these results support the concept of a multidisciplinary approach in the assessment and management of DCM.

Keywords: ADC; DTI; FA; MEP; MRI; SSEP; degenerative cervical myelopathy (DCM), surgical outcome; neurophysiology; signal changes spinal canal.

Figure 1

A: Measurement levels for fractional anisotropy (FA) and the apparent diffusion coefficient (ADC): The surgical level, or the narrowest point of the cervical stenosis in patients with multilevel compression (level 2), and the intervertebral levels above and below it (level 1 and 3). B, C: Diffusion tensor imaging (DTI) sequences for FA and ADC measurement, respectively.

Figure 2

Difference of trends of the average modified Japanese Orthopedic Association (mJOA) scores in the “best responders” and “normal responders” patients. The improvement from the preoperative score to the 1-year value in the “best responders” group was significant (p = 0.001), as the difference between the 1-year values of the “best responders” (mean = 16.3) and the “normal responders” (mean = 13.3) patients (p = 0.001).

Figure 3

Differences between fractional anisotropy average values of the most compressed level in best responders (blue) and normal responders (red) patients.

Figure 4

Preoperative abnormal values of motor evoked potentials (MEPs) were related to worse mJOA scores: This inverse correlation was statistically significant (r = −0.59, p = 0.0004).

Figure 5

A: Inverse correlation between preoperative FA values and L1 spinous process (N22) (p = 0.001). B: Inverse correlation between preoperative FA values and popliteal fossa to L1 (N8–N22) (p = 0.007).

Figure 6

Positive correlation between preoperative FA and mJOA at 1 year (p = 0.004, r = 0.66).

Figure 7

A: Significant correlation between preoperative FA value at the most compressed level and the 1-year postoperative variation of the mJOA (p = 0.002). B: Significant correlation between preoperative FA average value and the 1-year postoperative variation of the mJOA (p = 0.0002).