INTRODUCTION: Movement disorders are not rare in demyelinating diseases but 
there are few studies comparing their frequency between multiple sclerosis and 
neuromyelitis optica spectrum disorder. Our aim was to determine the frequency 
and the related features of movement disorders in a cohort of patients with 
multiple sclerosis and neuromyelitis optica spectrum disorder.
METHODS: It is a cross-sectional study of patients with multiple sclerosis and 
neuromyelitis optica spectrum disorder. Patients were evaluated by a movement 
disorder specialist. Data from a personal interview and neurological examination 
were collected. Fahn-Tolosa-Marin tremor rating scale was used for tremor 
evaluation. Health-related quality of life was assessed using EuroQol 
instrument.
RESULTS: Two hundred fifty-three patients were included (mean [SD] age, 40 [12] 
years; 74.3% female; median [IQR] EDSS score 2.5 [1.0-6.0]); 26% presented with 
movement disorders. Paroxysmal dystonia (n = 32) and tremor (n = 27) were the 
most common movement disorders. Patients with multiple sclerosis and low 
Expanded Disability Status Scale score (below 4.0) have fewer movement disorders 
than patients with neuromyelitis optica spectrum disorder. The diagnosis of 
neuromyelitis optica spectrum disorder was strongly associated with paroxysmal 
dystonia (OR = 22.07, 95% CI = 2.56-189.78; p = 0.005). Patients with multiple 
sclerosis and patients without movement disorders have a slightly better quality 
of life.
CONCLUSIONS: Paroxysmal dystonia was the most common movement disorder in 
demyelinating diseases and strongly associated with neuromyelitis optica 
spectrum disorder.