Psychiatric morbidity in patients with Parkinsons disease following bilateral subthalamic deep brain stimulation: literature review

Objective: To provide a comprehensive review and evaluation of the literature pertaining to the psychiatric sequelae of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). Methods: A structured search of the EMBASE, PsychINFO and MEDLINE databases was performed on articles published since the first use of STN DBS in 1993 for PD until March 2007. Non-human studies were excluded, along with studies reporting on unilateral DBS and studies reporting on the use of STN DBS for indications other than idiopathic PD. Ninety-seven articles were selected for inclusion in the review. Results: Patients with advanced PD have a high rate of psychiatric morbidity. STN DBS has been shown to be an effective treatment for the control of motor symptoms in advanced PD. Neurobehavioural side-effects are, however, relatively common following STN DBS. Side-effects include impaired executive function and verbal fluency, depression, hypomania, apathy, postoperative delirium, anxiety disorders and psychotic symptoms, especially hallucinations. The alteration in dopaminergic medication following surgery as well as the direct effect of STN stimulation both appear to contribute to the short-term and long-term postoperative psychiatric complications. Methodological issues that limit the applicability of the current literature in this field are highlighted. Conclusions: STN DBS is an effective treatment for the motor symptoms of advanced PD. However, further research is needed to assess the extent to which STN DBS contributes to or exacerbates psychiatric morbidity over and above that associated with advanced PD. Careful neuropsychiatric evaluation and monitoring are required in this patient group.