Electromyographic findings in the intrinsic muscles of normal feet.

Four intrinsic muscles were studied with electromyography (EMG) in asymptomatic feet in 70 individuals to ascertain the percentage having abnormal potentials (positive sharp waves and/or fibrillation potentials). The number having positive sharp waves ranged from 6(8.6%) in the 1st dorsal interosseous to 11(15.7%) in the extensor digitorum brevis. The number showing fibrillation potentials ranged from 0 for the abductor hallucis to 4(5.7%) for the abductor digiti minimi. The authors concluded that using positive sharp waves as a diagnostic criterion in using EMG of intrinsic foot muscles in the evaluation of certain neuromuscular problems such as radiculopathy and tarsal tunnel syndrome may be misleading, but using the presence of fibrillation potentials as a criterion may be useful. Differences in the pattern of abnormalities in males and females are also discussed.