Abstract

Hirayama disease (HD) is a focal Anterior Horn Cells (AHC) disease due to dynamic compression causing upper limb atrophy mainly young male. This is an observational retrospective study of 42 cases who attended Neurology Department from 2021 to 2023. In our study all are male, aged 12 to 42 years, majorly below 25 years. Most cases presented late on an average of 13.7 months. Significant number of bilateral presentations were seen in our study (47%). It is right hand predominant having both unilateral and bilateral cases. “Reverse split hand syndrome” observed in 90% cases and forearm weakness and atrophy significantly over medial aspect sparing Brachioradialis (93%). Polyminimyoclonus is a significant finding noted in 88% cases, Deep Tendon Reflexes (DTRs) are usually preserved except 14% cases in which triceps jerk is reduced. Nerve Conduction Study (NCS) shows > 50% reduction of Ulnar CMAP in affected side where Median Compound Muscle Action Potential (CMAP) is relatively preserved and Ulnar/Median CMAP ratio

Key words: Compound muscle action potential, Electromyography, Hirayama dis-ease, Nerve conduction study