Predictors of the emergence of apathy after bilateral stimulation of the subthalamic nucleus in patients with Parkinson's disease.

BACKGROUND: Subthalamic nucleus deep brain stimulation (STN-DBS) is a valid therapeutic tool that ameliorates motor symptoms in patients with Parkinson's disease (PD). However, apathy is one of the neuropsychiatric complications that may occur after STN-DBS surgery, and this may adversely influence the quality of life of patients despite significant motor improvement. OBJECTIVE: This study aimed to elucidate preoperative predictive factors for the presence of postoperative apathy in patients treated with STN-DBS. METHODS: Twenty-five consecutive PD patients receiving bilateral STN-DBS were recruited. The assessment instruments include modified Hoehn & Yahr stages, Unified Parkinson's Disease Rating Scale motor (part III) and dyskinesia (part IVa) scores, Parkinson's Disease Questionnaire-39 scores, Self-Rating Depression Scale scores, and Apathy Scale scores. Predictive factors for postoperative apathy were assessed. RESULTS: While STN-DBS resulted in a significant improvement in motor symptoms, six patients (24%) developed significant apathy after surgery. In multiple logistic regression analyses, preoperative severity of dyskinesia was found to be an independent predictor for the acute phase of postoperative apathy with STN-DBS (odds ratio = 89.993, p = 0.003). CONCLUSIONS: This study suggests that preoperative dyskinesia may predict postoperative apathy in the acute phase in patients with PD treated with STN-DBS. The pathogenesis of postoperative apathy remains unknown, but in patients with severe dyskinesia before STN-DBS, attention should be given to monitoring for postoperative apathy.