Sensory nerve conduction studies of the superficial peroneal nerve in L5 radiculopathy

Theoretically, sensory nerve action potential (SNAP) of the superficial peroneal nerve (SPN) should be preserved when L5 roots are damaged. Previous study indicated that SNAP of SPN was lost or reduced in amplitude in patiens with L5 radiculopathy. To address this issue, this study compared results of SPN sensory conduction studies between healthy subjects and patients with L5 radiculopathy.

Ninety-four healthy subjects were enrolled and assigned to two age groups: group I (< or = 60 years, n=61) and group II (> 60 years, n=33). Forty-one patients with unilateral L5 radiculopathy were enrolled by our electrodiagnostic laboratory between July 2000 and July 2003 and assigned to two age groups: 60 years or below (n=19) and above 60 years (n=22).

SPN response was found to be abnormal in only 1.6% of group I healthy subjects, but absent or abnormal SPN response was noted in 21.1% of patients with L5 radiculopathy of the same age group (p=0.01). However, a greater proportion of (27.3%) our healthy subjects above 60 years had abnormal SPN responses. This proportion was similar to that of patients with L5 radiculopathy and abnormal SPN response (31.8%) (p=0.72).

SPN sensory responses are reliably obtained in most healthy subjects under 60 years of age. Absence of SNAP or reduced SNAP amplitude of SPN on the side of their lesions did not necessarily exclude the diagnosis of L5 radiculopathy in the patients under 60 years of age.