Neuropsychological Issues in Deep Brain Stimulation of Neurological and Psychiatric Disorders

Abstract

The past decade has seen an explosion in the number of medically refractory conditions and neuroanatomical structures targeted for DBS treatment. While a review of the literature and meta-analyses indicate DBS for movement disorders to be safe from a neurobehavioral standpoint it is also clear that a small subset of patients have experienced moderate or severe neurobehavioral morbidity. If one combines the various cognitive and psychiatric morbidities reported across studies, approximately 10% of patients with PD undergoing DBS have experienced one or another neurobehavioral adverse events. Furthermore, several small studies have indicated that improvements in motor symptoms and quality of life (QOL) may not necessarily translate into social readjustment. A greater role for ancillary health services, such as speech therapy, occupational and physical therapy, neuropsychology, and psychotherapy needs to be contemplated. Health care providers should not rely on subjective impression or spontaneous patient report to identify neurobehavioral and psychosocial issues. Recent consensus statements on patient selection, treatment, and outcome evaluation should facilitate greater uniformity in outcome reporting and identification of neurobehavioral risk.What has proved elusive is the identification of reliable predictors and risk factors for such neurobehavioral changes. Ethical concerns and methodological limitations hinder the initiation of more sophisticated, controlled, blinded, comparative trials with large numbers of subjects needed to isolate predictors of neurobehavioral and QOL outcomes. Similarly, it is difficult to conclude at present that stimulation alone is associated with neurobehavioral morbidity, though in some cases, there are replicable effects on mood and cognition when stimulation is turned on and off. In the case of PD, and likely many of the disorders for which DBS is beginning to be investigated, outcomes may be related to an interaction of the surgical procedure and stimulation as well as subsequent changes in medications, psychosocial factors and pre-operative vulnerability. Conclusions that DBS is neuropsychologically safe in conditions such as dystonia, depression, obsessive compulsive diorder (OCD), Tourette syndrome (TS), epilepsy, multiple sclerosis (MS) and others must be considered highly preliminary until NJ 400 A.I. Tröster et al.adequate controlled trials are completed. The emergence of cognitive and social neuroscience studies of DBS, particularly when accompanied by functional neuroimaging, are encouraging signs that DBS may be used as a vehicle to better understand the cognitive and behavioral roles of the basal ganglia.