Is diffusion anisotropy a biomarker for disease severity and surgical prognosis of cervical spondylotic myelopathy?

PURPOSE

To explore the value of diffusion-tensor (DT) imaging in addressing the severity of cervical spondylotic myelopathy (CSM) and predicting the outcome of surgical treatment.

MATERIALS AND METHODS

From July 2009 to May 2012, 65 volunteers were recruited for this institutional review board-approved study, and all gave informed consent; 20 volunteers were healthy subjects (age range, 41-62 years), and 45 were patients with CSM (age range, 43-86 years). Anatomic and DT 3.0-T magnetic resonance images were obtained. Surgical decompression was performed in 22 patients with CSM, and patients were followed up for 6 months to 2 years. The clinical severity of myelopathy and postoperative recovery were assessed by using the modified Japanese Orthopaedic Association (mJOA) score. A recovery ratio (comparison of postoperative with preoperative mJOA score) of more than 50% indicated a good clinical outcome of surgery. DT findings, patient age, T2 high signal intensity (HSI), and somatosensory evoked potential (SEP) were analyzed by using a logistic regression model to predict the surgical outcome of patients with CSM.

RESULTS

A significant difference in cervical cord mean fractional anisotropy (FA) was found between healthy subjects and patients with CSM (0.65 ± 0.05 [standard deviation] vs 0.52 ± 0.13, P < .001). FA values were significantly correlated with the severity of neurologic dysfunction indicated by mJOA score (r(2) = 0.327, P = .016). Logistic regression analysis showed that mean FA (P = .030) and FA at the C2 vertebra (P = .035) enabled prediction of good surgical outcome; however, preoperative mJOA (P = .927), T2 HSI (P = .176), SEP amplitude (P = .154), and latency (P = .260) did not.

CONCLUSION

FA is a biomarker for the severity of myelopathy and for subsequent surgical outcome.