September 17, 1999

New device helps restore function to paralyzed larynx

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VUMC researchers are testing a novel implantable pulse generator like the one illustrated above to help patients with paralyzed vocal folds breathe on their own.

New device helps restore function to paralyzed larynx

by Barb Cramer

Doctors at Vanderbilt University Medical Center have developed a new implantable device that helps patients with paralyzed vocal folds breathe on their own.

The new device for bilateral paralysis of the larynx is an Implantable Pulse Generator (IPG) that allows a patient to speak and breathe normally. The device was recently implanted — for the first time ever in the United States — in a Missouri woman.

"We are excited about the possibilities with this electrical pacing device," said David L. Zealear, Ph.D., associate professor of Otolaryngology and director of research in the department. "The idea is to restore the opening function of the larynx to allow inhaling and exhaling necessary to normal breathing. We are able to restore that function,"

With the device, Zealear says, an electrode is inserted next to the opening muscle of the larynx sandwiched between the cricoid cartilage and the muscle.

"It involves electrical stimulation of the critical laryngeal muscle that has been paralyzed. The stimulation is done at the precise moment that the patient inhales, allowing the patient to take a breath," Zealear said.

The lead wire from the electrode is then brought subcutaneously through a tunnel to an incision below the clavicle. A pocket is made at that incision site and the stimulator is placed in that pocket. It can be re-programmed through the skin by using a microprocessor, Zealear said.

"When the stimulus is discontinued, the muscles passively relax back to their midline position to allow normal voice production and airway protection."

Zealear says about 6,000 patients are stricken with bilateral laryngeal paralysis each year in the United States. The condition is created primarily when the two nerves that serve the larynx become paralyzed due to neck surgery.

"Both the opening and closing functions are lost on both sides. The patient can not breathe and is in a life-threatening situation. For acute paralysis, the patient must have an emergency tracheotomy," Zealear said.

In case of chronic bilateral paralysis, conventional treatments focus on permanently opening the airway through surgical resection, leaving the patient with no chance of ever speaking normally again.

The first patient to be implanted with the IPG is Helen Burns, a 65-year-old Gallatin, Mo., housewife. (A second patient has now been fitted with an IPG device, but still has a tracheotomy in place.)

Burns developed bilateral paralysis of the larynx after a second goiter surgery four years ago. A tracheotomy was put in so she could breathe.

The IPG device was implanted 16 months ago and doctors have been watching her progress. After repeated tests, including pulmonary function tests and tread mill tests (to measure breathing capacity) and endoscopic tests (to view the stimulated movement of the vocal folds), Burns tracheotomy tube was removed 18 months ago.

"She has done really well," Zealear said. "We find that her ventilation with the IPG is working just as well as when she used her tracheotomy tube."

And Burns is pleased with the device.

"It's wonderful to be able to breathe and to not have a trach. It's brought back my life and has helped me so much. I can do almost anything now," Burns said.

The IPG puts out 12 stimulations per minute, which fits the average inhalation schedule of Burns.

"She is able to entrain her breathing with the stimulated breaths of the IPG subconsciously. She doesn't think about it. She just automatically does it," Zealear said.

Should the device fail for some reason, Zealear says Burns has sufficient ventilation to sustain life until she can get to a hospital for an emergency tracheotomy. The batteries that run the device are expected to last five years.

Burns has also been injected with botox (botulinum toxin, a man-made poison) treatment to relax the tone of her larynx muscles, which had become constricted. The botox treatment allows Burns to exhale, completing the breathing cycle.

The botox injection also allows increased air flow during voice production and has actually improved the quality of her voice, according to Cheryl Rainey, Ph.D. assistant professor of Otolaryngology and speech pathologist.

"The lack of airflow through her restricted airway made her voice sound very strained and tight. Botox reduced the tension in the vocal folds and restored her normal voice. This is an important finding since conventional surgical treatments for bilateral paralysis usually sacrifice voice production to create a larger airway," Rainey said.

Dr. Mark S. Courey, assistant professor of Otolaryngology, and Dr. James L. Netterville, associate professor of Otolaryngology, assisted in the investigation. Zealear developed the idea of using electrical stimulation of a muscle to restore function while a graduate student, and pursued the idea more vigorously with a National Institutes of Health Grant in 1990.