Motor Symptom Asymmetry Predicts Cognitive and Neuropsychiatric Profile Following Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease: a 5-Year Longitudinal Study

Abstract

Introduction: Risk factors (e.g., motor symptom asymmetry) for short- and long-term cognitive and neuropsychiatric symptoms following deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson's disease have yet to be fully identified. The objectives of the present study were to determine whether motor symptom asymmetry in Parkinson's disease is one such risk factor and to identify predictors of subnormal cognitive decline.

Methods: A total of 26 patients receiving STN-DBS (13 with left-sided motor symptoms and 13 with right-sided ones) underwent follow-up neuropsychological, depression and apathy assessments over a 5-year period. Nonparametric intergroup comparisons were performed on raw scores, as well as Cox regression analyses on standardized Mattis Dementia Rating Scale scores.

Results: Compared with patients who had predominantly left-sided symptoms, right-sided patients scored higher on both apathy (at 3 months and 36 months) and depressive symptoms (at 6 months and 12 months) and scored lower on global cognitive efficiency (at 36 months and 60 months). Survival analyses revealed that only right-sided patients had subnormal standardized dementia scores, which were negatively associated with the number of perseverations in the Wisconsin Card Scoring Test.

Conclusion: Right-sided motor symptoms are a risk factor for more severe short- and long-term cognitive and neuropsychiatric symptoms following STN-DBS, confirming literature findings on left hemispheric vulnerability.

Keywords: Cognition; Cognitive vulnerability; Left hemisphere; Motor symptom asymmetry; STN-DBS.

Fig. 1

Study flowchart. Note. GPi: internal globus pallidus; LPD: patients with PD exhibiting predominantly left-sided motor symptoms; PD: patients with Parkinson’s disease; DBS: deep brain stimulation; RPD: patients with PD exhibiting predominantly right-sided motor symptoms; SD: standard deviation; STN-DBS: subthalamic nucleus deep brain stimulation; VIM: ventral intermediate nucleus of the thalamus.

Fig. 2

Psychiatric changes over 5-year period following STN-DBS among patients living with Parkinson’s disease, differentiated according to motor symptom asymmetry (predominantly left-sided or right-sided PD). (A) Changes in apathy symptoms (AES) from pre-DBS to 60-month post-DBS. (B) Changes in depressive symptoms (MADRS) from pre-DBS to 60-month post-DBS. Note. AES: Apathy Evaluation Scale; MADRS: Montgomery-Åsberg Depression Rating Scale; pre-DBS: preoperative condition; post-DBS: postoperative condition; SD: standard deviation. ^** Significant results after FDR correction for within- and between-group differences are marked with colored asterisks.

Fig. 3

Stepwise forward Cox regression survival analyses for whole PD group and motor symptom asymmetry subgroups (left-sided PD and right-sided PD). Analysis revealed similar patterns of results for the whole group and right-sided subgroup. Note. pre-DBS: preoperative condition; post-DBS: postoperative condition.