“…We found 32 studies on the effect of DBS on PA in PD, including 723 patients. 37.5 % (n = 12) were retrospective observational before-after studies [52] , [53] , [54] , [55] , [56] , [57] , [58] , [59] , [60] , [61] , [62] , [63] , 40.6 % (n = 13) were Case Reports [64] , [65] , [66] , [67] , [68] , [69] , [70] , [71] , [72] , [73] , [74] , [75] , [76] , 18.75 % (n = 6) were Case Series [77] , [78] , [79] , [80] , [81] , [82] , and 1 was a Case-control study [83] . Twenty-seven studies evaluated the effect of bilateral subthalamic DBS (STN-DBS) [52] , [70] , [71] , [54] , [55] , [56] , [57] , [58] , [59] , [61] , [62] , [63] , [64] , [66] , [67] , [68] , [73] , [74] , [75] , [77] , [78] , [79] , [80] , [81] , [82] , [83] , [84] , six studies the effect of bilateral globus pallidus par interna DBS (GPi-DBS) [53] , [65] , …”