Extensor digitorum brevis reflex in normals and patients with radiculopathies.

This prospective study evaluated the extensor digitorum brevis deep tendon reflex (EDBR) in a normal population and in patients with L-5 and S-1 radiculopathies. There were 88 subjects: 53 normals, 17 L-5, and 18 S-1 radiculopathy subjects. The clinical EDBR revealed a 91% specificity, with 18% sensitivity for L-5, and 11% for S-1. The electrodiagnostic EDBR yielded increased sensitivities of 35% for L-5 (P = 0.07) and 39% for S-1 (P = 0.04), with 87% specificity. H-reflexes showed 50% sensitivity for the S-1 group (P = 0.0006) and 91% specificity. EDBR latencies were significantly related to age and leg length (r2 = 0.46, P < 0.0001). Age alone explained 26% (P < 0.0001) of the EDBR variability and leg length 20% (P < 0.0001). EDBR clinical and electrodiagnostic reflexes have low sensitivities, high specificities, and do not discriminate L-5 from S-1 root involvement.