Caregiver burden worsens in the second year after subthalamic nucleus deep brain stimulation for Parkinson's disease

https://doi.org/10.1016/j.parkreldis.2020.06.036Get rights and content

Highlights

  • Scant data exists on long-term effects of DBS on caregiver burden in PD.

  • We demonstrated that PD caregiver burden worsens in the second year after DBS.

  • Caregiver burden worsens despite PD motor improvement.

  • Caregiver burden after DBS does not correlate with executive dysfunction.

  • Contribution of non-motor symptoms to caregiver burden may explain our findings.

Abstract

Background

Caregiver burden (CB) in Parkinson's disease (PD) does not improve in the short term after bilateral subthalamic nucleus (STN) deep brain stimulation (DBS), despite motor improvement. This may be due to increased caregiver demands after surgery or the possibility that DBS unresponsive non-motor factors, such as executive dysfunction, contribute to CB.

Objective

To evaluate the trajectory of CB in year 2 following bilateral STN DBS surgery for PD, and to test whether post-operative CB changes correlate with changes in executive function in a subgroup with available neuropsychological testing.

Methods

This retrospective analysis included 35 patients with PD whose caregivers completed the Caregiver Burden Inventory (CBI) at baseline and between 9 and 24 months after bilateral STN DBS. 14 of these patients had neuropsychological testing both at baseline and within 6 months of their follow up CBI assessment.

Results

CBI scores showed worsened CB from baseline to follow-up (16.4–21.5, p = 0.006). There was no correlation between change in executive function and change in CBI in the smaller subsample.

Conclusion

CB worsens in the 2 years after bilateral STN DBS despite improvement in motor symptoms and is not associated with change in executive dysfunction in the setting of advancing PD. These findings have implications on pre-operative counselling for patients and caregivers considering DBS for PD.

Introduction

Caring for a loved one with a long-term medical condition has challenging emotional, social, financial, and even physical and psychiatric consequences for the caregiver [1], with such manifestations often referred to as caregiver burden (CB) [2]. Caregivers of patients with Parkinson's disease (PD) have been found to carry high levels of CB [3,4].

Deep brain stimulation (DBS) surgery is an effective treatment for motor symptoms of PD and improves quality of life [5]. Its impact on CB, however, is more uncertain. The few studies that have evaluated CB after DBS are limited by lack of specified follow up intervals, combination of different DBS targets into the same analytic cohort, and cross-sectional designs [5,6]. Studies focused on subthalamic nucleus (STN) DBS employ short-term follow up intervals after surgery for outcome assessments [[7], [8], [9]]. Given the increased frequency of visits occurring in the months following DBS surgery, CB may be transiently increased, and not accurately reflect long-term outcomes.

Our group previously demonstrated that CB does not improve 6 months after bilateral STN DBS for PD, despite improvement in motor function [10]. We hypothesized that CB may increase initially following DBS surgery due to elevated caregiver demands after brain surgery and frequent follow up visits to optimize DBS settings, only to later improve when motor function has stabilized. However, in non-DBS PD patients, non-motor symptoms such as cognition, mood/apathy, and psychosis, appear to impact CB more than motor symptoms [11]. We previously reported that family-reported executive dysfunction at baseline, as measured by the disinhibition subscale of the Frontal Systems Behavioral Scale (FrSBe), positively correlated with baseline CBI [10]. Since we would not expect executive dysfunction to improve with STN DBS, CB would be unlikely to improve after surgery if executive dysfunction is the major contributor to CB.

Few studies have examined the longer term changes in CB following STN-DBS. Once programming parameters have been optimized and stabilization of motor symptoms achieved, some relief in burden may be experienced by caregivers. To examine this possibility, this study looked at CB up to 2 years following PD STN DBS surgery. We hypothesized an improvement in CB associated with the longer postoperative period. In a subgroup with detailed executive function cognitive testing, we also assessed whether post-operative changes in executive function related to CB.

Section snippets

Methods

This retrospective study involved data collected from the University of Michigan Surgical Therapies Improving Movement (STIM) DBS program. Selection criteria for DBS candidacy at our institution have previously been described [12]. Briefly, candidates must have a clinical diagnosis of PD, with motor complications despite optimal medication management, or a disabling, medication non-responsive tremor. Patients are ineligible for surgery if they have significant, untreated psychiatric illness or

Results

Table 1 reports patient baseline characteristics including means, standard deviation (SD), and count data for the 35 patient larger cohort and for the subset of 14 patients with pre- and post-operative neuropsychological testing data. There were no significant differences in baseline characteristics between the subset of 14 patients with neuropsychological testing and the entire cohort.

Change in CBI total score and sub-scores from baseline to follow-up are presented in Table 2. Mean total CBI

Discussion

Our findings suggest that the severity of CB progresses in the 2 years following STN DBS for PD, despite significant improvement in motor function. The reason for this discordance is unclear. In our subcohort, CBI progression does not appear to be driven by a worsening in executive functioning. This may be because executive function did not significantly change from baseline to after surgery. However, we also did not reproduce our previously reported association between baseline FrSBe and CBI [

Ethics

Study procedures were approved by the Institutional Review Board of the University of Michigan. Written informed consent was obtained from all participants for inclusion in the database. All authors contributed to study design, evaluation of data, and/or writing of the manuscript, and have approved the manuscript in its final form.

The authors have no declarations of interest relevant to this activity.

Dr. Jackowiak has received a honorarium from Medlink Neurology.

Dr. Maher has nothing to

Declaration of competing interest

The authors report no conflicts of interest related to the research covered in this article.

Acknowledgments

This project did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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