Monomelic amyotrophy with clinico-radiological and electrophysiological evaluation: A study from Eastern India

Monomelic amyotrophy (MMA) is a benign, rare, sporadic disorder of adolescent and young adults with male predominance, where neurogenic amyotrophy is restricted to an upper or lower limb. It is a variant of lower motor neuron disorder with insidious onset and slow progression for 2-4 years. Paucity of cohort studies as well as relative unawareness among physicians in eastern India stimulated us to do this work.

Prospective observational study involving 140 cases of MMA from 2012 to 2016, conducted at S.C.B.Medical College, cuttack, Odisha to evaluate clinical profile, electrophysiology and radiological features. All the data were analysed & subjected to statistical analysis through SPSS software version 24.

Mean age at onset and presentation were 19.6yrs and 21.7yrs respectively and the average duration 3.2yrs. Upper limb involvement was more common (91.4%) with distal affection (83%) more than proximal (7%). Isolated Leg amyotrophy found in 12 cases (~9%) and 10 cases were having thigh weakness & atrophy. B/L Upper Limb distal involvement was present in 18.5% cases asymmetrically. Family history found in~2.8%. Autonomic symptoms were present in affected and bilateral homologous Limb in 21%, 5.8%(~6%) patients. Changes in electromyography (EMG) were present in affected limb (100%) and clinically unaffected limb (15%).

MMA is a benign disease of young males with weakness and atrophy confined to unilateral limb or asymmetrical homologous limb and areflexia without sensory loss. It progresses variably for 2-3 years followed by stabilization without progression to Motor neuron disease.