Motor unit number estimation (MUNE) is unique technique that could estimate the numerical number of motor axons innervating target muscles. Since the original MUNE technique has been reported, extensor digitorum brevis (EDB) is widely used for estimating the number of motor units in clinical or experimental conditions. Although abductor hallucis (AH) has frequently been utilized for nerve conduction study rather than EDB, MUNE in AH has not been reported in Japan. We proposed the utility of MUNE in AH for clinical use in this study. Multiple point stimulation technique was performed to 16 healthy volunteers and 16 patients with amyotrophic lateral sclerosis (ALS) for calculating motor unit number of plantar muscles. The active electrode was placed on the motor point of AH and the reference electrode was over the corresponding proximal phalanx, according to traditional “belly-tendon recording”. The MUNE in ALS was significantly smaller than that in healthy controls, and has positive correlation with foot function of revised ALS functional rating scale. There are some questions of the basis to have accurate MUP on active electrode in this muscle. We then tested monopolar recording of AH to reject affection from inactive electrode in 12 healthy controls. The MUNE on AH using monopolar recording has positive correlation with that of belly-tendon recording. We consider that the MUNE recorded from AH using belly-tendon recording could reflect the reduction of motor unit number in ALS, and is useful as clinical and physiological parameter to investigate the plantar muscle pathology.

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[in Japanese]

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[in Japanese]

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