Effects of Transcutaneous Vagus Nerve Stimulation in Parkinson´s Disease

Universidade da Coruña46 enrolled

Overview

This study aims to determine whether electrical stimulation of the ear, when combined with physical and speech therapy, can improve symptoms in subjects diagnosed with Parkinson´s disease, by comparing two different application sites. Each subject will undergo an initial in-person screening and provide consent before participating in the study. The main questions to answer are: * Does transcutaneous electrical nerve stimulation (tVNS) in the ear paired with physical and speech therapy improve speech and voice-related problems, airway protection, salivation, and swallowing? * Does tVNS paired with physical and speech therapy improve tremor, walking speed, and balance in people with PD? * Does tVNS paired with physical and speech therapy improve heart rate and heart rate variability in people with PD? * Do its effects persist at 8 weeks? Participants will: Attend 12 rehabilitation sessions over 4 weeks (three per week). During each session, participants received either active or sham tVNS, accompanied by speech therapy (once per week), physical therapy (once per week), or conducted alone (once per week). Undergo speech, voice, swallowing, respiratory, gait, balance, tremor, heart rate variability, and cognitive testing, as well as questionnaires regarding the quality of life, before and after treatment. Return for a follow-up visit eight weeks after therapy to check how long the effects last.

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. Most people with PD will experience dysfunction of the autonomic nervous system (ANS), although the severity of this dysfunction can vary widely, affecting both physical and mental well-being. Symptoms are typically classified as motor or non-motor. Prominent motor symptoms of PD include bradykinesia, rigidity, tremor, and abnormalities in gait, balance, and posture. These symptoms are associated with falls and have a very negative impact on quality of life. In addition, impaired fine motor skills, combined with respiratory and other problems, significantly affect voice, speech, and swallowing, as well as other non-motor disorders, such as neuropsychiatric, sleep, sensory, and digestive disorders. This study is a double-blind, randomized, controlled trial designed to evaluate the efficacy of transcutaneous auricular vagus nerve stimulation on the motor and non-motor effects of Parkinson´s Disease (PD). Investigators will recruit up to 46 patients. The volunteers will be randomized by sex and the Hoehn and Yahr stage. Clinical information and, specifically, Unified Parkinson's Disease Rating Scale (UPDRS) -III (section III) will be assessed initially. The primary variable of the study will be voice variables, such as volume, jitter, and shimmer. The remaining dependent variables will be other voice and acustic measures; the presence and severity of dysphagia; the presence and severity of xerostomia and sialorrhea; swallowing efficiency, peak cough flow; the level of tremor; the severity of gait dysfunction; balance; cognitive ability regarding concentration and response inhibition; heart rate and heart rate variability; quality of life in PD; adverse effects; and the degree of effectiveness of blinding. Over the course of 4 weeks, participants will receive 30-minute stimulation sessions three times weekly, along with physiotherapy and speech therapy once per week. One group will be assigned to stimulation in the cymba concha (where the vagus nerve is placed) and the other (sham) in the earlobe. Data collection will occur at baseline (T0), post-intervention (T1- 4 weeks), and 8 weeks after finishing the intervention (T2), except for the intensity required to administer electrical stimulation and adverse effects, which will be studied during the whole intervention. Tolerance will be assessed on day 1 of stimulation and on day 12 (4 weeks). Statistical analyses will employ mixed-model approaches to evaluate changes in outcome measures over time and between interventions.

Interventions

Transcutaneous Electrical Nerve Stimulation (TENS) of Vagus NerveDEVICE

The tVNS will be performed at 200 microseconds, with frequencies ranging from 20 to 200 Hz (30 seconds/30 seconds) for 30 minutes, in the area innervated by the auricular branch of the vagus nerve (cymba concha and concha). The individually titrated intensity will be set above the sensory threshold (intense tingling sensation) but below the level of discomfort.

Conventional Physical therapyOTHER

Physical therapy delivered to both groups consists of exercises aimed at posture alignment and body coordination, static and dynamic balance improvement, and gait quality. It will be delivered once a week, during a session of electrical stimulation.

Conventional Speech TherapyOTHER

It will focus on the orofacial muscles, the acquisition of a diaphragmatic-abdominal breathing pattern that integrates breathing with vocal production, voice training with exercises that enhance vocal quality and prosody, articulation exercises to improve speech clarity, and swallowing training. It will be administered once a week, during one of the three electrical stimulation sessions.

Sham Transcutaneous Electrical Stimulation of Vagus NerveDEVICE

The sham- tVNS will be performed at 200 microseconds, with frequencies ranging from 20 to 200 Hz (30 seconds/30 seconds) for 30 minutes, with electrodes placed on the earlobe, which lacks vagus nerve innervation. The individually titrated intensity will be set above the sensory threshold (intense tingling sensation) but below the level of discomfort.

Eligibility

Sex: ALL

Medical Language ↔ Plain English

Inclusion Criteria: * Being a member of the Association or be interested in joining; * Idiopathic PD diagnosis, stages 2-3 according to the Hoehn \& Yahr scale; confirmed by neurologist * Ability to walk independently for at least 1 minute ant turn 180° without assistance; * Exhibiting symptoms of hypokinetic dysarthria; * On stable dopaminergic therapy for at least 1 month prior to the experiment Exclusion Criteria: * Any contraindication for taVNS (e.g., ear lesions, pacemakers, defibrillators, or other electronic devices) * Previous vagotomy or previous application of electrical stimulation to the ear or brain, or treatment with high-intensity focused ultrasound (HIFU) * Voice or speech disorders caused by other medical conditions * MoCA score below 21 * Psychotic symptoms or hallucinations; a diagnosis of psychiatric illness * Systolic blood pressure above 160 mm Hg, and diastolic blood pressure above 100 mm Hg * Inability to attend sessions; * Concomitant neurological, orthopaedic, cardiac, respiratory or active medical/oncological condition that would affect participation

Outcomes

Primary Outcomes

Voice intensity

The PRAAT software will be used to test the voice twice, when sustaining till 10 seconds the vowel "a" and when reading a text at their usual volume. The intensity (voice volume, measured in decibels) will be recorded.