Effect of Surface Electrical Stimulation on Movement of the Larynx

This study will examine whether surface electrical stimulation on the skin of the throat will: 1) move the larynx (voice box); 2) move the vocal folds in the larynx; and 3) cause less movement of the larynx when applied during swallowing. It is important that the larynx moves up and forward while swallowing so that food does not go into the airway. A device called VitalStim® (Registered Trademark), which provides electrical stimulation to the skin on the neck and under the chin, is widely used to treat people who have problems swallowing. This study will determine if VitalStim can move the voice box or the vocal folds in the larynx. This information is important for patients who have long-term problems raising or closing their larynxes when they swallow.

Healthy volunteers between 20 and 60 years of age may be eligible for this study. Candidates are screened with a medical history, physical examination, electrocardiogram, and nasoendoscopy. For the latter procedure, the inside of the subject's nose is sprayed with a decongestant, opening the nasal passages. A small flexible tube called a nasoendoscope is passed through the nose to the back of the throat. The scope allows observation of the larynx while the subject speaks, sings, whistles and makes prolonged vowel sounds.

Participants are familiarized with the VitalStim device before beginning the experimental procedures. The device consists of two sets of electrodes and a stimulation unit. The electrodes are placed on the neck and under the chin. Stimulation causes different sensations, according to the intensity level. They include "tingling/crawling," "vibrating" "warm/burning," and "grabbing." Subjects then undergo the following procedures:

• Nasoendoscopy with muscle stimulation: The inside of the nose is sprayed with a decongestant and the nasoendoscope is passed through one nostril to the back of the throat. Electrodes are placed on the throat area and under the chin. Stimulation is delivered 10 times at various places on the neck and under the chin while the subject sits quietly. This test shows if the vocal folds in the voice box move with surface electrical stimulation.
• Videofluoroscopy with muscle stimulation at rest and during swallowing: This is an x-ray study of the head and neck during swallowing and at rest to determine how stimulation affects the level of the voice box in the neck. Electrodes are placed under the chin and on the throat. The subject swallows 5 milliliters of barium, a contrast material that can be seen easily on x-ray. The x-ray machine is turned on for a few seconds at a time during each swallow of the barium and another 10 times while the subject is remaining still without swallowing.