Deep brain stimulation.

High-frequency deep brain stimulation (DBS) is an established therapy for Parkinson disease (PD), essential tremor, and primary dystonia, and is under investigation for several neuropsychiatric diseases. DBS for PD, in the subthalamic nucleus or globus pallidus interna (GPi), improves tremor, bradykinesia, and rigidity, emotional well-being and sleep, and "on" time without dyskinesias, but may not improve axial and cognitive impairment or speech. DBS in motor thalamus may improve or resolve rest, action, and postural tremor. DBS in the GPi results in functional improvement in hyperkinetic greater than tonic aspects of primary and tardive dystonias. Perioperative risks include hemorrhage and stroke (<2%) and infection (∼8%). The benefit/risk ratio may be optimized with individualized patient selection and the use of an experienced surgical team. DBS is expensive and well-placed unilateral ablation therapy has been shown to be efficacious. Bilateral ablations pose an unacceptable risk of speech impairment and disequilibrium.