Neuropsychological performance changes following subthalamic versus pallidal deep brain stimulation in Parkinson's disease: a systematic review and metaanalysis

Background. Studies comparing subthalamus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) for the management of Parkinson's disease in terms of neuropsychological performance are scarce and heterogeneous. Therefore, we performed a systematic review and metaanalysis to compare neuropsychological outcomes following STN DBS versus GPi DBS. Methods. A computer literature search of PubMed, the Web of Science, and Cochrane Central was conducted. Records were screened for eligible studies, and data were extracted and synthesized using Review Manager (v. 5.3 for Windows). Results. Seven studies were included in the qualitative synthesis. Of them, four randomized controlled trials (n = 345 patients) were pooled in the metaanalysis models. The standardized mean difference (SMD) of change in the Stroop color-naming test favored the GPi DBS group (SMD = -0.31, p = 0.009). However, other neuropsychological outcomes did not favor either of the two groups (Stroop word-reading: SMD = -0.21, p = 0.08; the Wechsler Adult Intelligence Scale (WAIS) digits forward: SMD = 0.08, p = 0.47; Trail Making Test Part A: SMD = -0.05, p = 0.65; WAIS-R digit symbol: SMD = -0.16, p = 0.29; Trail Making Test Part B: SMD = -0.14, p = 0.23; Stroop color-word interference: SMD = -0.16, p = 0.18; phonemic verbal fluency: bilateral DBS SMD = -0.04, p = 0.73, and unilateral DBS SMD = -0.05, p = 0.83; semantic verbal fluency: bilateral DBS SMD = -0.09, p = 0.37, and unilateral DBS SMD = -0.29, p = 0.22; Boston Naming Test: SMD = -0.11, p = 0.33; Beck Depression Inventory: bilateral DBS SMD = 0.15, p = 0.31, and unilateral DBS SMD = 0.36, p = 0.11). Conclusions. There was no statistically significant difference in most of the neuropsychological outcomes. The present evidence does not favor any of the targets in terms of neuropsychological performance.