Objectives:
Chronic pharyngeal dysphagia is a life threatening disorder following brain injury. Repeated occurrences of aspiration pneumonia result in expensive hospital stays and reduced survival. The purpose of this investigation is to compare two novel training methods: 1) training to initiate swallowing while pressing a switch; 2) training to initiate swallowing while pressing a switch with coincident peripheral vibrotactile stimulation.
Some preliminary studies will be conducted in healthy volunteers to determine the feasibility of using near infrared spectroscopy (fNIRS) for measuring change in brain activation for swallowing before and after treatment and to determine the physiological effects of direct current stimulation on brain activation for swallowing, during sensory stimulation and at rest.
Patients will be randomly assigned to one of two training groups and the results of 12 training sessions will be contrasted using blinded assessment. The hypothesis being tested is that training methods involving simultaneous peripheral-sensory stimulation will reduce the risk of aspiration or penetration during swallowing in patients with chronic pharyngeal dysphagia post brain injury.
Two additional questions address the neural mechanisms involved in the training effects. To determine whether changes occur in cortical control of the hyo-laryngeal musculature involved in swallowing, patients will also be studied before and after training using transcranial magnetic stimulation to assess muscle responses to cortical stimulation. Finally, to determine if training effects are related to changes in cortical neuroplasticity, we will use near infrared spectroscopy to measure functional change in brain activation in M1, for swallowing to determine if cortical control is enhanced in the different training groups.
Study Population:
Healthy volunteers and patients with chronic pharyngeal dysphagia following brain injury will be studied.
Design:
Healthy control subjects will be assessed first in three studies:
1. A study comparing the effects of air puff versus vibrotactile stimulation on inducing swallowing
2. A study of the transcranial magnetic stimulation to elicit responses from pharyngeal and submental muscles
3. A study using near infrared spectroscopy to examine brain activation responses to sensory stimulation, brain laterality for swallowing and the effects of transcranial direct current stimulation (tDCS) on brain responses to sensory stimulation and brain activation for swallowing.
Patients with chronic pharyngeal dysphagia following brain injury will participate in a clinical trial evaluating swallowing motor retraining with and without sensory stimulation. This study will be a randomized, blinded Phase 2 clinical trial in which patients will be assigned to two training conditions: training with sham sensory stimulation and training with vibrotactile sensory stimulation.
A non-invasive, external vibrotactile stimulator on the throat will provide external sensory stimulation. Pre-training testing, training sessions, and post-training testing will be provided in up to 20 visits for each subject.
Outcome Measures:
The primary outcome variables will be measures of swallowing function before and after training and at 3 and 6 months post training. These will include the NIH Swallowing Safety Scale scored from masked videofluoroscopy recordings and the Water Test, a non-invasive assessment of swallowing. Both will be scored by speech pathologists blinded to patient training group identity or condition before or after training.
To assess the relationship of improvements in training with changes in neuronal function, transcranial magnetic stimulation with surface electromyography recordings will be used to assess changes in corticobulbar conduction following training.
To assess whether functional activation within the brain (particularly in the region of M1) is related to improvement in swallowing following each type of training, near infrared spectroscopy NIRS will be used to examine blood oxygenation level dependent changes in brain function for swallowing following training. All outcome measures will be scored without knowledge of training group or condition (pre vs. post training or training group).
