Monomelic amyotrophy

**Definition:** Atrophy and weakness restricted to one upper or lower limb, onset in the second or third decade, male predominance, and sporadic occurrence are characteristic features of MMA. Other typical features include: insidious onset of lower motor neuron signs due to anterior horn cell involvement, absence of upper motor neuron signs, slow progression followed by stabilization within a few years,, and a benign symptomatic disease course. MMA is particularly prevalent in Asia although it is encountered worldwide.