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

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.

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.

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 mm²) than in both neutral (66.9 ± 22.3 mm²) and extension (68.3 ± 19.1 mm²). 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 mm² for SC and 99 mm² for CSF plus SC area.

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.