Neuropsychological outcome after unilateral pallidotomy for the treatment of Parkinson's disease

Objective-To assess the long term cognitive outcome of unilateral posterove ntral pallidotomy (PVP) and the overall efficacy of the surgery. Methods-Forty two (29 left and 13 right PVP) patients with Parkinson's dise ase underwent neurological and neuropsychological testing before PVP and at 3 and 12 months after PVP. The neuropsychological testing battery emphasis ed measures of verbal learning and memory, visuospatial abilities, speed of information processing, executive functioning, and affective functioning. Results-All patients demonstrated motor improvements after surgery during t heir off state, and 86% of patients also showed improvements in motor funct ioning in their on state. Repeated measures ANOVA showed significant improv ements in confrontational naming, visuospatial organisation, and affective functioning 3 months and 12 months after surgery, with inconsistent improve ments in executive functioning 12 months post-PVP Patients demonstrated a t ransient impairment in verbal memory, with verbal learning performance retu rning to baseline 12 months post-PVP after a significant decline 3 months a fter PVP. When three patients with lesions extending outside of the PVP wer e excluded from the analysis, a decline in verbal fluency performance after PVP was not found to be significant. Differences due to side of lesion pla cement were not found on any of the cognitive measures. Conclusions-In the largest long term follow up study reported to date, the cognitive changes found up to a year after PVP are minimal compared with th e robust improvements in motor function. The findings highlight the need to investigate the relation between the specific fibre tracts affected by the lesions and cognitive outcome.