Neuropsychology of deep brain stimulation in neurology and psychiatry.

Deep brain stimulation (DBS) experienced resurgence in the 1990s when limitations in pharmacotherapy and ablative surgery for movement disorders (including neuropsychological deficits) were appreciated. Subthalamic DBS for Parkinson's disease has received the most empirical attention and may entail cognitive and psychiatric adverse events in approximately 10% of patients. This article reviews the cognitive alterations after thalamic, pallidal, and subthalamic DBS for movement disorders (including, Parkinson's disease, essential tremor, and dystonia) and the possible etiology and mechanisms underlying neurobehavioral changes. Initial studies of neurobehavioral outcomes of DBS for emerging indications such as epilepsy, obsessive compulsive disorder, depression, Tourette's syndrome, and persistent vegetative or minimally conscious state are also reviewed. DBS for currently accepted indications appears safe from a cognitive standpoint in that the procedure is associated with typically transient, mild, and circumscribed cognitive alterations (most commonly in verbal fluency), and improved mood state and quality of life. A minority of patients experience more widespread, persistent, or serious cognitive and psychiatric sequelae, although research to date has failed to identify reliable risk factors for such adverse events.