Sonographic evaluation of sciatic nerves in patients with unilateral sciatica

Abstract

Objectives: To evaluate the sciatic nerves of patients with unilateral sciatica by using an ultrasound, and to determine whether ultrasonographic findings were related to clinical and electrophysiologic parameters.

Design: Cross-sectional study.

Setting: Physical medicine and rehabilitation departments of a university hospital and a rehabilitation hospital.

Participants: Consecutive patients (N=30; 10 men, 20 women) with complaints of low back pain and unilateral sciatica of more than 1 month of duration were enrolled.

Interventions: Not applicable.

Main outcome measures: All patients underwent a substantial clinical assessment, and they were also evaluated by electromyogram and magnetic resonance imaging. Pain was evaluated by a visual analog scale and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) Scale. A linear array probe (7.5-12MHz) was used to scan sciatic nerves bilaterally in the prone position. Sciatic nerve diameters-thickness (short axis) and width (long axis)-and cross-sectional areas were measured bilaterally at the same levels, proximal to the bifurcation and midthigh. The values pertaining to the unaffected limbs were taken as controls.

Results: When compared with the unaffected sides, mean values for sciatic nerve measurements-long axis at bifurcation level (P=.017) and cross-sectional area at midthigh level (P=.005)-were significantly larger on the affected sides. Swelling ratios negatively correlated with symptom duration (r=-.394, P=.038) and LANSS scores (r=-.451, P=.016) at only midthigh level.

Conclusions: Sciatic nerves seem to be enlarged on the side of sciatica in patients with low back pain. Our preliminary results may provide insight into better understanding the lower limb radiating pain in this group of patients.