Basal ganglia injury as a complication of the ketogenic diet.

Movement disorders or basal ganglia injury have not been reported as complications of the ketogenic diet, an alternative treatment for intractable epilepsy. We report on a novel complication of the ketogenic diet manifesting as a severe extrapyramidal movement disorder and bilateral putaminal lesions. A single case is described. A video demonstrating the movement disorder is included. A 5-year-old girl with a cryptogenic epileptic encephalopathy developed focal dystonia, diffuse chorea, and ataxia after starting the ketogenic diet. Cranial magnetic resonance imaging (MRI) demonstrated bilateral putaminal lesions that were not present before starting the diet. MR spectroscopy showed a lactate peak in the basal ganglia, suggesting a failure of mitochondrial energy metabolism as the mechanism of cerebral injury. The radiographic abnormalities resolved after stopping the diet, although the movement disorder persisted. Basal ganglia injury and extrapyramidal movement abnormalities are potential complications of the ketogenic diet. Concomitant use of valproate or a latent inborn error of metabolism may be risk factors for these rare complications.