Lower stimulation frequency can enhance tolerability and efficacy of pallidal deep brain stimulation for dystonia

We report the case of a patient with medically refractory primary dystonia who was treated with bilateral pallidal deep brain stimulation. Stimulation at 130 Hz or higher, by means of the more ventral contacts generated capsular side effects, which made their use impractical. Consequently, the patient was treated for 9 months at 130 to 185 Hz, by means of the more dorsal contacts, achieving modest results. By reducing the stimulation frequency to 80 Hz, we were able to activate the ventral contacts without inducing side effects. Within days, the patient experienced a dramatic improvement in function that has persisted for 1 year. A further reduction in stimulation frequency to 60 Hz resulted in a worsening of his symptoms. We conclude that chronic stimulation at frequencies of <100 Hz may be efficacious in dystonia and may enhance the tolerability of stimulation by means of contacts that are positioned posteroventrally within the internal globus pallidus, nearer the internal capsule.