Nerve root sleeve diameters at normal segments and at segments with proximate disc disease: MRI evaluation

Objective: To compare MR morphologic parameters of spinal nerve roots and their range of variability in normal and abnormal spinal segments. Design and patients: Ninety-six consecutive lumbar spine MRI examinations were segregated into three groups: group 1 was composed of 30 patients with disc bulge, protrusion or extrusion at the L5-S1 segment measuring 3 mm or more; group 2 consisted of 31 patients with no disc pathology; and group 3 was composed of 35 patients with no disc abnormality at the L5-S1 level but with coexisting spine pathology at other segments. Measurements of 192 S1 nerve root sleeves were performed at three consecutive levels on T1-weighted images. Differences between right and left nerve root sleeve diameters (delta value) at three slice levels were calculated in each group. Data were analyzed by ANOVA. Results: No significant differences between the mean values of traversing S1 nerve root sleeve diameter on three corresponding consecutive slices were found among groups (P=0.733, P=0.824, P=0.365 respectively), nor were significant differences in delta values between groups found (P=0.639, P=0.113, P=0.722). Conclusions: S1 nerve root sleeve diameter and the differences between right and left in the abnormal group were not significantly different from normal and therefore can not be used as an objective criterion of nerve root pathology.