Scatter graphs showing the relationships between postoperative changes of UPDRS part III off and total scores on WAIS-R. X-, and Y-axis indicates postoperative changes of UPDRS part III off score and those of verbal intelligence quotient (VIQ), performance intelligence quotient (PIQ), and total scores on WAIS-R, respectively. Postoperative changes in UPDRS part III off were significantly related to those in PIQ (R2 = 0.39, P = 0.039), but not in VIQ (R2 = 0.024, P = 0.65) and total score (R2 = 0.18, P = 0.19). UPDRS: unified Parkinson's disease rating scale, WAIS-R: Wechsler adult intelligence scale-revised.