Objective Apathy has been reported as a possible adverse effect of deep brain stimulation of the subthalamic nucleus (STN-DBS). We investigated the prevalence and severity of apathy in 22 patients with Parkinson's disease (PD) who underwent STN-DBS and the effects on quality of life (QOL).

Method All patients were assessed with the Lille Apathy Rating Scale (LARS), the Apathy Scale (AS) and the Parkinson's Disease Questionnaire and were compared to a control group of 38 patients on pharmacotherapy alone. The relationship between apathy and clinico-demographic variables was explored through correlation analysis.

Results Apathy was reported by a similar proportion of patients in the two groups: 18.4% in the DBS group and 22.7% in the control group according to LARS ratings; 45.5% in the DBS group and 42.1% in the control group according to AS ratings. There was no significant difference in apathy or QOL ratings between the two groups. Significant correlations were observed between poorer QOL and degree of apathy, as measured by the LARS (p<0.001) and AS (p=0.021). PD-related disability also correlated with both apathy ratings (p><0.001 and p=0.017, respectively).

Conclusion Our findings suggest that STN-DBS is not associated with changes in apathy in the PD population, as there was no difference in prevalence or severity of apathy between patients who had undergone STN-DBS and those on pharmacotherapy alone. More severe apathy was associated with a higher level of disability due to PD and worse QOL in PD but no other clinico-demographic characteristics.