Bilateral atrophy of the extensor digitorum brevis muscle might be a useful sign for diagnosing diabetic polyneuropathy in Japanese men who do not sit in the traditional “seiza” style

AIMS/INTRODUCTION: As the extensor digitorum brevis muscle is a small muscle in the most distal part of the legs, its atrophy (EDBA) might reflect symmetric polyneuropathy (SPN). We aimed to clarify the EDBA‐related factors and the usefulness of bilateral EDBA detection for diagnosing SPN, especially diabetic SPN (DSPN). MATERIALS AND METHODS: In 1,893 participants from the Japanese general population (investigation I) and 133 established diabetes patients (investigation II), relationships between EDBA and various factors including the traditional sitting style called “seiza’” (kneeling and sitting on one’s heels) were investigated. Analyses were carried out by univariate and multivariate analysis, and SPN or DSPN was diagnosed by the criteria of “Probable DSPN” of the Toronto Consensus. The validity of EDBA detection for diagnosing SPN/DSPN was also evaluated. RESULTS: Investigation I: EDBA was more prevalent in women than men (44% vs 20%). Significant EDBA‐related factors were aging and seiza habit regardless of sex. Male‐specific EDBA‐related factors were SPN and known diabetes. In men without seiza habit, EDBA was significantly associated with SPN regardless of diabetes, so EDBA seemed to be a useful sign for diagnosing SPN/DSPN. Investigation II: In men, DSPN was more prevalent in the EDBA group than the non‐EDBA group (71% vs 33%). Sensitivity, specificity, positive predictive value and kappa coefficient of EDBA detection for diagnosing DSPN were 44, 87, 67% and 0.323, showing fair agreement. CONCLUSIONS: EDBA detection might be a useful method to screen for distal symmetric polyneuropathy, such as DSPN in men, although the exclusion of individuals with seiza habit is necessary to improve accuracy.