Cognitive Outcome After Deep Brain Stimulation for Refractory Obsessive-Compulsive Disorder: A Systematic Review.

INTRODUCTION Deep brain stimulation (DBS) is an effective treatment for refractory obsessive-compulsive disorder (OCD). Neuropsychological assessment contributes to DBS treatment in several ways: it monitors the cognitive safety of the treatment, identifies beneficial or detrimental cognitive side effects and it could aid to explain variability in treatment outcome, and possibly the treatment's working mechanism(s). BACKGROUND This systematic review assessed the cognitive safety of DBS for OCD and explored whether changes in cognitive function may help explain its working mechanism(s). MATERIALS AND METHODS EMBASE, PubMed/Medline, Psycinfo, and the Cochrane Library were systematically searched for studies reporting cognitive outcomes following DBS for OCD. Searches were completed in November 2020. Included studies were appraised for study design and quality according to National Heart, Lung and Blood Institute (NHLBI) quality assessment tools. RESULTS Five randomized controlled trials and ten observational studies comprising a total of 178 patients were analyzed collectively. Variable outcomes of DBS were observed in the domains of attention, memory, executive functioning, and in particular cognitive flexibility. CONCLUSION Although individual studies generally do not report cognitive deterioration after DBS for OCD, the variability of study designs and the multitude of cognitive measures used, precluded a meta-analysis to confirm its safety, and recognition of a cognitive pattern through which the efficacy of DBS for OCD might be explained. In future, prospective studies should preferably include a standardized neuropsychological assessment battery specifically addressing executive functioning and have a longer-term follow-up in order to demonstrate the cognitive safety of the procedure. Such prospective and more uniform data collection may also contribute to our understanding of the working mechanisms of DBS in OCD.