Analysis of Morphometric Parameters in Cervical Canal Stenosis on Neutral and Dynamic Magnetic Resonance Imaging

OBJECTIVE: A dynamic compression injury of the cervical spinal cord (SC) is widely accepted in the pathophysiology of cervical myelopathy. Flexion/extension magnetic resonance imaging (MRI) provides information on the dynamic cervical injury. We sought to compare morphometric parameters on neutral and flexion/extension MRI in cervical spondylotic myelopathy. METHODS: Patients with cervical canal stenosis who had MRI in neutral, flexion, and extension positions were reviewed retrospectively. A morphometric comparison of following parameters at compression level was performed: SC area, cerebrospinal fluid (CSF) area, and CSF reserve ratio (CSF/CSF plus SC). Patients were classified according to the presence of high signal (HS) in SC, and predictors of HS were calculated by the use of logistic regression analysis. - RESULTS: In total, 55 patients, 26 men, with mean age of 57 +/- 13 were analyzed. Significant difference was found in mean CSF reserve ratio between flexion and extension (0.47 +/- 0.18 vs. 0.40 +/- 0.21, P < 0.05). SC area was significantly smaller in flexion (58.8 +/- 13.3 mm(2)) than in both neutral (66.9 +/- 22.3 mm(2)) and extension (68.3 +/- 19.1 mm(2)). HS was found in 22 cases, and predictors of HS were smaller SC area on extension (odds ratio 1.46; 95% confidence interval 1.07-1.84) and smaller CSF plus SC area on flexion (OR 1.32; 95% confidence interval 1.06-1.45). Cut-off values on the receiver operating characteristic curve were 55 mm(2) for SC and 99 mm(2) for CSF plus SC area. CONCLUSIONS: Application of dynamic MRI in cervical stenosis reveals significant differences of both SC and CSF reserve ratio in flexion/extension and neutral positions. Patients with smaller SC area in extension and smaller CSF plus SC area in flexion have greater risk of HS on MRI.