Electromyographic examination of gluteal muscles in the differential diagnosis of lumbar herniated discs.

The aim of the present investigation was to establish the value of gluteal muscles (m.gluteus medius, GME; m.gluteus maximus, GMX) as segmental reference muscles in the topical diagnosis of lumbar root compression syndromes. The methodological rationale consisted in determining the frequency with which denervation potentials could be recorded in the GME and GMX of patients with clinically and electromyographically well-defined monosegmental or bisegmental lumbar root compression syndromes. Of the L5-syndromes (N=36), 81% revealed denervation potentials in GME, but only 6% in GMX. Of the S1 syndromes (N=26), 63% exhibited denervation potentials in GMX and 32% in GME. L5 syndromes showed a better correlation of positive findings to GME than S1 syndromes to GMX. As far as the differential diagnosis is concerned, the advantages of recording EMG from GME and GMX are two-fold: (a) the immediate certainty of excluding a peripheral nerve lesion and (b) a reduction in the incidence of false negative findings.