Narrow cervical canal in 1211 asymptomatic healthy subjects: the relationship with spinal cord compression on MRI.

Purpose: Narrow cervical canal (NCC) has been a suspected risk factor for later development of cervical myelopathy. However, few studies have evaluated the prevalence in asymptomatic subjects. The purpose of this study was to investigate the prevalence of NCC in a large cohort of asymptomatic volunteers.
Methods: This study was a cross-sectional study of 1211 asymptomatic volunteers. Approximately 100 men and 100 women representing each decade of life from the 20s to the 70s were included in this study. Cervical canal anteroposterior diameters at C5 midvertebral level on X-rays, and the prevalence of spinal cord compression (SCC) and increased signal intensity (ISI) changes on MRI were evaluated. Receiver operating characteristic analysis was performed to determine the cut-off value of the severity of canal stenosis resulting in SCC.
Results: NCC (<14 mm) was observed in 123 (10.2 %) subjects. SCC and ISI were found in 64 (5.3 %) and 28 (2.3 %) subjects, respectively. The prevalence of NCC was significantly higher in females and older subjects, but the occurrence of severe NCC (<12 mm) did not increase with age. The canal size in subjects with SCC or ISI was significantly smaller than in those without SCC (p < 0.0001). The cut-off values of cervical canal stenosis resulting in SCC were 14.8 and 13.9 mm in males and females, respectively.
Conclusions: The prevalence of NCC was considerably lower among asymptomatic healthy volunteers; the cervical canal diameter in subjects with SCC or ISI was significantly smaller than in asymptomatic subjects; NCC is a risk factor for SCC.