Evaluation of atrophy of foot muscles in diabetic neuropathy -- a comparative study of nerve conduction studies and ultrasonography.

OBJECTIVE: To evaluate the relation between the findings at nerve conduction studies and the size of small foot muscles determined by ultrasonography.
METHODS: In 26 diabetic patients the size of the extensor digitorum brevis muscle (EDB) and of the muscles between the first and second metatarsal bone (MIL) was determined. Motor nerve conduction studies of the peroneal and tibial nerves were performed with determination of the amplitudes of the CMAPs and of the nerve conduction velocities (NCV). Further, a standardised clinical examination was performed providing a neurological impairment score.
RESULTS: Seventeen patients fulfilled the criteria for diabetic neuropathy. The cross-sectional area of the EDB muscle and the thickness of the MIL muscle were 116 +/- 65 mm2 and 29.6 +/- 8.2 mm, respectively. Close relations were established between muscle size and the amplitude of the CMAP of the peroneal (r=0.77, p<0.001) and of the tibial nerve (r=0.70, p<0.01). Further there were close relations between the muscle size and the NCV of the peroneal (r=0.62, p<0.01) and of the tibial nerve (r=0.71, p<0.001).
CONCLUSIONS: The amplitude of the CMAP of the peroneal and of the tibial nerves is closely related to the size of the small foot muscles as determined by ultrasonography. SIGNIFICANCE: In diabetic patients motor nerve conduction studies can reliably determine the size of small foot muscles.