Objective: To evaluate cognitive effects of subthalamic nucleus (STN) deep brain stimulation (DBS) in Parkinson’s disease (PD) and to investigate whether subclinical autonomic dysfunction may predict cognitive decline after STN DBS.

Background: Cognitive impairment is a recognized non-motor symptom of PD and autonomic dysfunction has been proposed as a mechanistic factor. STN DBS has been associated with neuropsychological side effects [1,2]. Studies focusing on predictive factors of cognitive outcome have yielded conflicting results.

Method: We followed 28 PD patients selected for STN DBS. Autonomic status (spectral analysis of heart rate variability (HRV) and baroreflex gain) and broad neuropsychological assessments at baseline and post-surgery were performed.  Linear regression analyses and Pearson’s test were performed to estimate the correlation between subclinical dysautonomia and cognitive change scores.

Results: Patients baseline characteristics are shown [table 1]. Mean follow-up time post-surgery was 7.8±5.4 months. Unified Parkinson’s Disease Rating Scale (UPDRS) part III score significantly reduced after DBS (p<0.001). Phonetic verbal fluency (PhVF) worsened significantly after STN DBS (p=0.012) and a tendency to a decline in Trail B making test performance was observed (p=0.061) [table 2]. Lower baseline values of high frequency of HRV (reduced lower autonomic tonus) correlated with a greater decline in PhVF after surgery, even after age adjustment (P<0.001) [figure 1]. This seems independent from a DBS effect on autonomic function as only a slight decrease in baroreflex alpha gain was observed (p=0.043) [table 3]. Change in PhVF was not correlated with baseline motor score (p=0.80) or PhVF (p=0.81).

Conclusion: We found a subtle cognitive decline, predominantly affecting PhVF, in line with the literature [2]. This is the first study suggesting that subclinical dysautonomia may render patients specifically vulnerable to accelerated cognitive decline post-DBS, whilst the relationship is probably multifactorial. If confirmed in larger cohorts, testing for HRV could be a simple non-invasive method for better patient selection for DBS and for prognosis information regarding cognitive outcomes.

References: 1. McDonald C, Newton JL, Burn DJ. Orthostatic hypotension and cognitive impairment in Parkinson’s disease: Causation or association? Mov Disord. 2016;31(7):937-46; 2. Combs HL, Folley BS, Berry DT, Segerstrom SC, Han DY, Anderson-Mooney AJ, Walls BD, van Horne C. Cognition and Depression Following Deep Brain Stimulation of the Subthalamic Nucleus and Globus Pallidus Pars Internus in Parkinson’s Disease: A Meta-Analysis. Neuropsychol Rev. 2015;25(4):439-54.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dysautonomia-as-a-predictor-of-cognitive-outcome-after-deep-brain-stimulation-in-parkinsons-disease/