Finger extension weakness and downbeat nystagmus motor neurone disease (FEWDON-MND)

Atypical motor neurone disease (MND) represents a challenging and expanding group of neurodegenerative disorders involving the upper or lower motor neurones, and rarely both. Neuro-ophthalmological disturbances such as gaze-evoked downbeat nystagmus are extremely rare in the context of typical and atypical MND. Finger extension weakness and downbeat nystagmus motor neurone disease (FEWDON-MND) syndrome has been recently recognised as a distinct syndromic phenotype of MND, with a characteristic clinical picture. We describe a 63-year-old woman with long-standing lower motor neurone involvement of the upper limbs, who on examination had gaze-evoked downbeat nystagmus. After extensive negative investigation for secondary causes of MND and downbeat nystagmus, we diagnosed FEWDON-MND syndrome.