Atypical motor neuron disease variant: facial-onset sensory and motor neuronopathy syndrome (FOSMN)

Abstract

Background Facial-onset sensory and motor neuronopathy (FOSMN) is a rare disease whose cardinal features are initial asymmetrical facial sensory deficits slowly evolving and followed by bulbar symptoms and spreading of sensory and motor deficits from face to scalp, neck, and extremities. Case presentation We described a 70-year-old man who presented with 6-month history of facial numbness on the left side, and gradual worsening of symptoms. Over several months, facial muscle weakness, dysarthria, and fasciculation had progressed. NCS, needle EMG and blink reflex responses suggested the diagnosis of FOSMN. The ganglioside panel (anti-GM1 and Gd1b) was positive. Considering the FOSMN autoimmune pathology hypothesis, IVIG treatment was given. Conclusion In this case, we aimed to highlight the key clinical aspects of FOSMN and how to differentiate it from motor neuron disease and bring FOSMN to the attention of neurologists as a recently recognized and distinctive disorder.