Comparison of seven different scales used to quantify severity of cervical spondylotic myelopathy and post-operative improvement.

Considerable uncertainty exists over the benefit that patients receive from surgical decompressive treatment for cervical spondylotic myelopathy (CSM). Such difficulties might be addressed by accurate quantification of CSM severity as part of a trial determining the outcome of surgery in different patient groups. This study compares the applicability of various existing quantitative severity scales to measurement of CSM severity and the effects on severity of surgical decompression. Scores on the following scales were determined on 100 patients with CSM preoperatively and then again six months following surgical decompression: Odom's Criteria, Nurick grade, Ranawat grade, Myelopathy Disability Index (MDI), Japanese Orthopaedic Association (JOA) Score, European Myelopathy Score (EMS) and Short Form-36 Health Survey (SF36). All the scales showed significant improvement following surgery. However, each had differing qualities of reliability, validity and responsiveness that made them more or less suitable. The MDI showed the greatest sensitivity between different severity levels, sensitivity to operative change and reliability. However, analysis of all the questionnaire scales into components that looked at different aspects of function revealed potential problems with redundancy and a lack of consistency. This prospective observational study provides a rational basis for determining the advantages and disadvantages of different existing scales in measurement of CSM severity and for making adaptations to develop a scale more specifically suited to a comprehensive surgical trial.