Evaluation of extensor digitorum brevis thickness in healthy subjects: A comparative analysis of nerve conduction studies and ultrasound scans

- Extensor digitorum brevis (EDB) thickness was closely associated with fibular nerve CMAP in healthy subjects.
- EDB thickness was greater in men compared to women and decreased significantly with age.
- Muscle thickness with ultrasound is a potentially useful measure of distal neuromuscular function.

Objectives(1) To evaluate the relationship between the thickness and compound muscle action potential (CMAP) of the extensor digitorum brevis (EDB) muscle; (2) to obtain reference values for distal lower extremity muscle thickness as a possible measure of peripheral neuropathy; and (3) to evaluate various factors associated with unexplained EDB atrophy.MethodsWe measured the thickness of EDB, abductor hallucis brevis (AHB) and tibialis anterior (TA) muscles in 80 healthy volunteers with ultrasound and assessed EDB CMAP with fibular nerve stimulation. Two foot muscle-associated lifestyle factors were assessed and sociodemographic information was collected.ResultsA significant correlation was observed between the amplitude of the fibular nerve CMAP and EDB thickness. The thickness of each of the three muscles was greater in men compared to women. EDB thickness decreased significantly with age although the thicknesses of the AHB and TA muscles were not correlated with age.ConclusionsEDB thickness was closely associated with fibular nerve CMAP but with less variation and differed among groups by age and sex; it was not associated with lifestyle factors.SignificanceThe ability to obtain this measure painlessly with ultrasound and its low variation recommend it as a potentially useful complementary measure of distal neuromuscular function.