ObjectiveTo describe an adult patient with Rasmussen’s disease with focal dystonia as the most disabling symptom and the good response to unilateral globus pallidus internus (GPi) deep brain stimulation (DBS).MethodsRetrospective review of clinical records and diagnostic tests.ResultsThe patient had displayedmild focal seizures with sensory and motor symptoms on the left arm and hemiface since the age of 22. Ten years later she experienced abrupt onset of focal left dystonia involving mainly the leg. Brain MRI showed progressive right hemisphere atrophy, and ¹⁸fluorodeoxyglucose-positron emission tomography (¹⁸FDG-PET) showed right hypometabolism mainly over the frontal and insular regions. Brain biopsy confirmed chronic encephalitis. The dystonia became very severe and made walking extremely difficult. Different treatments including dopaminergic, anticholinergic, immunomodulatory drugs and botulinum toxin were ineffective. Finally the patient was treated with unilateral GPi DBS. Shortly after the onset of the stimulation, the dystonia started to improve. Parameters have been adjusted, and 18 months after surgery the patient is able to walk and run unaided, although a mild left leg dystonia persists.ConclusionRasmussen’s disease may be difficult to diagnose in adult patients. Associated movement disorders may be more disabling than seizures. Focal dystonia may be treated successfully with DBS.