# Effect of deep brain stimulation on dysphagia in Parkinson’s disease: mechanisms, evidence, and outlook

## TL;DR

This paper reviews how deep brain stimulation affects swallowing in Parkinson’s disease, finding mixed results and suggesting future research directions.

## Contribution

The paper provides a critical review of DBS effects on dysphagia in PD and outlines future research needs based on current pathophysiological understanding.

## Key findings

- Subthalamic DBS shows variable effects on swallowing outcomes in PD patients.
- Pallidal DBS has limited evidence of impact on swallowing function.
- Patient-reported outcomes often differ from instrumental assessments in DBS studies.

## Abstract

Oropharyngeal dysphagia (OD) is a common and significant complication of Parkinson’s disease (PD), contributing to malnutrition, respiratory complications and impaired medication intake. The pathophysiology of OD in PD is heterogeneous, involving basal ganglia dysfunction with associated motor impairments in the oropharynx, cortical pathophysiology, and α-synuclein pathology in peripheral nerves. While deep brain stimulation (DBS) is an established intervention for motor symptom management in PD, its effects on swallowing function remain poorly understood and controversial. This narrative review aims to critically evaluate the current evidence on the effects of DBS on OD in PD and to outline potential future research directions, grounded in current understanding of OD pathophysiology and DBS mechanisms.

A narrative review of clinical studies examining the effects of DBS on swallowing function in people with PD was conducted. Studies were identified through database searching of MEDLINE, Embase and Cochrane Library, from inception of the databases until May 2025. Inclusion criteria encompassed clinical studies and case reports investigating DBS effects on swallowing outcomes in people with PD, with no language restrictions applied. Data regarding study design, DBS intervention and stimulation parameters, swallow-related outcomes and assessment methods were extracted and compiled systematically.

A total of 24 clinical studies, including prospective and retrospective observational studies and case reports, were included in this review. Evidence regarding DBS effects remains inconsistent. Subthalamic DBS shows the greatest variability: some studies report improvements in aspiration frequency or pharyngeal timing, while others describe no change or even long-term deterioration in swallowing safety. Pallidal DBS appears to neither improve nor deteriorate swallowing function, however, evidence is limited to four mainly retrospective studies with small sample sizes. Evidence on combined or alternative targets remains sparse and heterogeneous. Patient-reported swallowing outcomes are often more favorable than instrumental measures.

DBS may influence swallowing in PD, but outcomes likely depend on OD phenotypes, stimulation targets and parameters. Future research should recruit adequately powered cohorts, apply standardized instrumental assessments including detailed OD phenotyping, systematically explore stimulation parameters, distinguish short- from long-term effects, and integrate OD outcomes into DBS programming.