Clinical Utility of Repetitive Nerve Stimulation Test in Differentiating Multifocal Motor Neuropathy From Progressive Muscular Atrophy.

OBJECTIVES:To evaluate the utility of repetitive nerve stimulation test (RNS) for differentiating multifocal motor neuropathy (MMN) and progressive muscular atrophy (PMA). METHODS:We retrospectively enrolled 20 patients with MMN or PMA. We extracted the results of the initial 3-Hz RNS in the ulnar and accessory nerves and compared the percentage and frequency of abnormal decremental responses between both groups. RESULTS:RNS was performed in 8 ulnar and 9 accessory nerves in patients with MMN, and in 8 ulnar and 10 accessory nerves in patients with PMA. Patients with MMN had a significantly lower decrement percentage (0.6 ± 4.0% in MMN vs. 10.3 ± 6.5% in PMA, P < 0.01) and frequency of abnormal decremental response (0 of 9 in MMN vs. 6 of 10 in PMA, P = 0.01) than patients with PMA in the accessory nerve. CONCLUSIONS:The RNS has clinical utility for differentiating MMN from PMA.