Hypoglossal neuropathy in Lewis-Sumner syndrome masquerading as motor neuron disease

Lewis-Sumner syndrome (LSS) is a peripheral neuropathy characterized by multifocal weakness and wasting and associated sensory impairment1 considered to be a variant of chronic inflammatory polyneuropathy (CIDP). LSS is associated with multifocal persistent conduction block and other signs of demyelination.1,2 We report a patient with probable LSS presenting with tongue hemiatrophy thought to have motor neuron disease. ### Case report. A 56-year-old man with chronic alcoholism presented to the neuromuscular clinic with a 6-year history of progressive painless right arm weakness and right hand paresthesias and a 2-year history of left arm weakness, burning pain, and numbness in the feet, and falls. On evaluation by another neurologist immediately following symptom onset, he was found to have tongue atrophy and fasciculations, right arm weakness and wasting, and decreased sensation in the right hand. MRI of the brain and cervical spinal cord, anti-GM1 antibodies, and genetic testing for Kennedy’s disease were unrevealing. Electrodiagnostic study, limited to sensory and motor nerve conduction study of the right median and ulnar nerves, demonstrated a mildly prolonged median distal motor latency and reduced median sensory nerve conduction velocity across …