Caregiver burden and caregiver appraisal of psychiatric symptoms are not modulated by subthalamic deep brain stimulation for Parkinson’s disease

www.nature.com/npjparkd ARTICLE OPEN Caregiver burden and caregiver appraisal of psychiatric symptoms are not modulated by subthalamic deep brain stimulation for Parkinson’s disease Philip E. Mosley 1,2,3,4 , Michael Breakspear1, Terry Coyne3,5, Peter Silburn2,3 and David Smith 1 Subthalamic deep brain stimulation is an advanced therapy that typically improves quality of life for persons with Parkinson’s disease (PD). However, the effect on caregiver burden is unclear. We recruited 64 persons with PD and their caregivers from a movement disorders clinic during the assessment of eligibility for subthalamic DBS. We used clinician-, patient- and caregiver-rated instruments to follow the patient–caregiver dyad from pre- to postoperative status, sampling repeatedly in the postoperative period to ascertain fluctuations in phenotypic variables. We employed multivariate models to identify key drivers of burden. We clustered caregiver-rated variables into ‘high’ and ‘low’ symptom groups and examined whether postoperative cluster assignment could be predicted from baseline values. Psychiatric symptoms in the postoperative period made a substantial contribution to longitudinal caregiver burden. The development of stimulation-dependent mood changes was also associated with increased burden. However, caregiver burden and caregiver-rated psychiatric symptom clusters were temporally stable and thus predicted only by their baseline values. We confirmed this finding using frequentist and Bayesian statistics, concluding that in our sample, subthalamic DBS for PD did not significantly influence caregiver burden or caregiver-rated psychiatric symptoms. Specifically, patient–caregiver dyads with high burden and high levels of psychiatric symptoms at baseline were likely to maintain this profile during follow-up. These findings support the importance of assessing caregiver burden prior to functional neurosurgery. Furthermore, they suggest that interventions addressing caregiver burden in this population should target those with greater symptomatology at baseline and may usefully prioritise psychiatric symptoms reported by the caregiver. npj Parkinson’s Disease (2018)4:12 ; doi:10.1038/s41531-018-0048-2 INTRODUCTION Caregivers make a substantial contribution to the support of people with Parkinson’s disease (PD). In 2014, Australian PD caregivers provided 19 million hours of care, equivalent to $AUD 78.2 million ($USD 59.5 million).1 The PD caregiver may need to coordinate multidisciplinary treatment, advocate for additional services, administer medication, assist with personal care, prevent falls and provide emotional support. However, caregivers are at risk of burden, defined as ‘the extent to which caregivers perceive that caregiving has had an adverse effect on their emotional, social, financial, physical and spiritual functioning.’2 Burden is associated with adverse psychiatric outcomes amongst caregivers,3,4 and may reduce the effectiveness and tolerability of caregiving, resulting in earlier use of state-sponsored services or premature institutionalisation. PD is a complex disorder manifesting motor and non-motor symptoms, both of which may amplify caregiver burden. Psychiatric symptoms, including depression, anxiety, apathy, psychosis, cognitive impairment and impulsecontrol disorders (ICDs) have consistently been associated with higher levels of burden.5 The cumulative prevalence of psychiatric and cognitive comorbidity in PD is estimated to be >50%,6 with contributions from neurodegeneration, adverse effects of treatment and psychological reactions to progressive disability. Deep brain stimulation (DBS) is an advanced therapy for PD that involves neurosurgery to position electrodes in deep brain nuclei. These produce continuous electrical stimulation to modulate disordered basal ganglia activity. Individuals with motor complications of drug therapy that receive DBS may have a better outcome than those maintained on medication alone, expressed as an improvement in motor symptoms, a reduced requirement for dopaminergic medication and a better self-rated quality of life.7,8 However, DBS is not a treatment for psychiatric symptoms in PD, which may continue to progress postoperatively. Furthermore, new psychiatric problems may also emerge, related to the titration of stimulation, the withdrawal of dopaminergic medication and to the inevitable psychosocial adaptation that follows relief of disability in a patient–caregiver dyad.9 (Note, although we prefer to use the term ‘person with PD’, we occasionally employ the term ‘patient’ when this role is contrasted with that of ‘caregiver’). The subthalamic nucleus (STN) is the most common surgical target for DBS in Australasia. However, the anatomy of this nucleus confers vulnerability to stimulation-dependent cognitive and affective disinhibition.10–12 Accordingly, some persons with PD become more impulsive and less empathic after DBS, acting recklessly without foresight or concern for others, potentially 1 Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD, Australia; 2Neurosciences Queensland, St Andrew’s War Memorial Hospital, Spring Hill, QLD, Australia; 3Queensland Brain Institute, University of Queensland, St Lucia, Brisbane, QLD, Australia; 4Faculty of Medicine, University of Queensland, Herston, QLD, Australia and 5Brizbrain and Spine, The Wesley Hospital, Auchenflower, QLD, Australia Correspondence: Philip E. Mosley () Received: 3 December 2017 Revised: 14 March 2018 Accepted: 23 March 2018 Published in partnership with the Parkinson’s Foundation Burden after Deep Brain Stimulation PE Mosley et al. 1234567890():,; 2 increasing caregiver burden.13 The incidence of this syndrome has been estimated at between 1 and 15%.14,15 Early reports noted relational conflicts subsequent to STN-DBS, linked to perceived behavioural changes in the person with PD, despite a good motor outcome and in the absence of significant relational difficulties prior to DBS.16,17 Prior research has suggested that as many as 50% of caregivers rate their wellbeing as negative following STN-DBS, despite positive patient-rated outcomes. Psychiatric symptoms are significant covariates of negative caregiver ratings.18 Importantly, patient and caregiver ratings of postoperative affective changes are frequently discrepant.19 Despite its clinical importance, the main factors influencing post-DBS caregiver burden, indeed whether burden increases or decreases after DBS, remain unclear. The objective of this study was to examine the trajectory and determinants of caregiver burden in a consecutive sample of persons with PD referred for STN-DBS at one DBS centre in Australia. We employed a prospective, longitudinal design with repeated-measures sampling to capture fluctuations in motor and psychiatric symptoms as the patient–caregiver dyad progressed from pre- to postoperative status. A longitudinal investigation enables more accurate inferenc (...truncated)