IMPULSE CONTROL DISORDERS FOLLOW DEEP BRAIN STIMULATION OF THE SUBTHALAMIC NUCLEUS IN PARKINSON’S DISEASE CLINICAL ASPECTSCategory: Newsworthy Notes
Polyvios Demetriades,1 Hugh Rickards,1 and Andrea Eugenio Cavanna1,2,3 1University of Birmingham Medical School, Birmingham B152TT, UK 2Department of Neuropsychiatry, University of Birmingham and BSMHFT, Barberry Building, 25 Vincent Drive, Birmingham B152FG, UK 3Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, UCL, London WC1N 3BG, UK Received 14 October 2010; Accepted 7 January 2011 Academic Editor: Antonio Strafella Copyright © 2011 Polyvios Demetriades et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Parkinson’s disease (PD) is increasingly recognized as a neurodegenerative condition characterized by motor dysfunction and both physiological and psychological disturbances . Although PD has been classically associated with psychiatric comorbidities such as dementia  and psychosis , recent studies have shown that patients with PD can develop a variety of behavioral problems associated with impulse dyscontrol, including pathological gambling, hypersexuality, punding (repetitive purposeless motor acts not distressing to the patient), and compulsive shopping and eating . These pathological behaviors are currently classified as impulse control disorders (ICDs) and exert negative consequences in terms of the patients’ health-related quality of life, mainly because of the interference with their social functioning . The aetiopathogenesis of ICDs in patients with PD is not completely understood, but previous studies showed that dopamine replacement therapy can lead to the development of ICDs due to overstimulation of the mesolimbic dopaminergic system  which modulates behavioral responses to reward, motivation, and reinforcement. A recent large cross-sectional study has shown that up to 13.6% of patients with treated idiopathic PD may suffer from ICDs , with hypersexuality, pathological gambling, and compulsive shopping being the most common ones. Levodopa use, younger age of onset of PD, and unmarried status were associated with the development of ICDs. Other predictive factors included being male, history of alcohol abuse, and novelty seeking or impulsive personality traits . Finally, it has been consistently found that patients using dopamine agonists are more likely to develop ICDs (6.3%) than those using L-dopa (0.6%) .
In some patients, dopaminergic medication becomes less effective in treating motor symptoms. Deep brain stimulation (DBS) is an effective neurosurgical procedure that can reduce motor symptoms in patients with treatment-refractory PD (especially patients who developed levodopa-induced dyskinesia), thus allowing decrease in their medication . Consequently, DBS might have an indirect beneficial role in patients suffering from ICDs. However, DBS may also have detrimental effect on patients’ behaviours. The most effective target of DBS in PD is arguably the subthalamic nucleus (STN), which plays a part in the fronto-striato-thalamic-cortical loops mediating motor, cognitive, and emotional functions , thus suggesting that DBS may affect patients’ behavior, in addition to motor performance. Both case reports and clinical studies associating DBS with the postoperative development of ICDs have provided support to this hypothesis.
As the popularity of DBS increases and this neurosurgical procedure is offered to patients suffering from other treatment-resistant movement disorders commonly associated with ICDs, such as Tourette syndrome , there is a need of more conclusive results on its role in the development of ICDs. This literature review assesses the current evidence on the clinical implications of ICDs in patients with PD who underwent DBS of the subthalamic nucleus.
- Literature Search Methodology
We performed a literature search across the databases Medline, EMBASE, and PsycInfo to identify original studies and case reports which examined the behavioral effects of DBS in patients with PD, with focus on ICDs, as defined in Chapter 5 of the ICD-10 classification system . We used the search terms “Parkinson,” “deep brain stimulation”, “impulse control disorder”, “impulsivity”, “hypersexuality”, “pathological gambling”, “punding”, “compulsive shopping”, “compulsive eating”, and “addiction”, and we limited our search to papers published in English language.