Madras motor neuron disease (MMND) is a rare motor neuron disorder predominantly reported from Southern India, characterized by early onset, lower cranial nerve involvement, sensorineural hearing loss, and slow progression. Adolescent-onset MMND is exceptionally uncommon, and reports from outside India remain limited. Early recognition is crucial, as the condition can mimic amyotrophic lateral sclerosis (ALS) and riboflavin-responsive disorders such as Brown-Vialetto-Van Laere syndrome. A 26-year-old woman from Nepal presented with a 10-year history of progressive distal limb weakness, recurrent falls, and difficulty performing fine motor tasks beginning at age 16. She developed severe–profound bilateral sensorineural hearing loss and bulbar dysfunction, including dysarthria, dysphagia, and recurrent aspiration pneumonia. Examination revealed distal-predominant weakness, tongue fasciculations, mixed upper and lower motor neuron signs, and intact cognition. Nerve conduction studies showed reduced CMAP amplitudes with preserved SNAPs, suggesting motor axonopathy; EMG demonstrated chronic denervation across bulbar, cervical, and lumbosacral segments. MRI brain and spine were normal. Metabolic, autoimmune, infectious, and paraneoplastic evaluations were unremarkable. Audiometry confirmed profound bilateral SNHL, and OCT showed no optic atrophy. Her clinical profile was highly consistent with classical MMND. This case reflects an exceptionally early-onset and slowly progressive MMND phenotype. Compared with reported variants featuring cerebellar atrophy, minimal hearing loss, or rapid deterioration, this patient demonstrated profound deafness, preserved imaging, and a decade-long gradual decline. The presentation underscores the disease’s heterogeneity and the importance of distinguishing MMND from ALS and BVVL syndrome. This case represents the first known MMND presentation from Nepal, underscoring the need for regional awareness of this rare but distinctive motor neuron disorder This report highlights a rare adolescent-onset MMND case outside India, demonstrating the characteristic triad of motor neuron involvement, bulbar dysfunction, and severe sensorineural hearing loss. Greater awareness and further research into genetic and environmental contributors are essential to better understand this uncommon disorder. • First documented case of Madras motor neuron disease reported from Nepal. • Adolescent-onset MMND with decade-long slow progressive motor decline. • Profound bilateral sensorineural hearing loss as a defining clinical feature. • EMG and NCS confirm motor axonopathy with preserved sensory pathways. • Normal MRI distinguishes MMND from ALS and riboflavin-responsive mimics.
Sapkota et al. (Fri,) studied this question.