Mood and cognitive changes with deep brain stimulation. What we know and where we should go

The aim of this study was to completely review the literature on cognitive and mood changes resulting from deep brain stimulation (DBS), and to examine the factors that might lead to these changes. DBS has been shown to improve motor symptoms in many movement disorders. Despite the widespread use of this technique, there are relatively few well controlled studies describing the potential cognitive, mood and behavioral consequences that may result from DBS. Additionally, the factors that may influence these changes have not been carefully studied.

A complete survey of the articles exploring the effects of DBS on mood and cognition was performed. Each study identified was examined and categories of factors that may have influenced mood and cognition were noted. These factors included surgical target, number of patients studied, whether procedures were unilateral or bilateral, average age of patients, diagnosis, condition of the DBS during the study (on or off), pre-operative screening tests (e.g., dementia rating scale, mini mental state exam), and changes on mood and cognitive tests (categorized as no change, improved, or worsened). Studies were divided into evidence-based categories.

There are many mood and cognitive changes that may result from DBS. Due to methodological limitations of existing studies there are important unanswered questions about cognitive and mood changes resulting from this type of surgery. The predominant amount of data regarding changes in mood and cognition with DBS is level 3 or case based evidence.

There exists a paucity of well-controlled studies addressing the mood and cognitive changes that result from DBS. Carefully performed prospective studies may help us to understand the effects of DBS on mood and cognition.