The spectrum of movement disorders in Glut-1 deficiency.

To assess the spectrum of movement disorders, we reviewed video recordings and charts of 57 patients with Glut-1 deficiency. Eighty-nine percent of patients with Glut-1 deficiency syndrome had a disturbance of gait. The most frequent gait abnormalities were ataxic-spastic and ataxic. Action limb dystonia was observed in 86% of cases and mild chorea in 75%. Cerebellar action tremor was seen in 70% of patients, myoclonus in 16%, and dyspraxia in 21%. Nonepileptic paroxysmal events occurred in 28% of patients, and included episodes of ataxia, weakness, Parkinsonism and nonkinesogenic dyskinesias. The 40 patients (70%) who were on the ketogenic diet had less severe gait disturbances but more dystonia, chorea, tremor, myoclonus, dyspraxia, and paroxysmal events compared with the 17 patients on a conventional diet. Poor dietary compliance and low ketonuria appear to trigger the paroxysmal events in some patients. Gait disturbances and movement disorders are frequent in patients with Glut-1 deficiency and are signs of chronic and intermittent pyramidal, cerebellar and extrapyramidal circuit dysfunction. These clinical symptoms reflect chronic nutrient deficiency during brain development and may be mitigated by chronic ketosis.