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Study aims to change standard of care for laryngeal paralysis

Feb. 14, 2019, 9:58 AM

David Zealear, Ph.D., works in the Department of Otolaryngology’s Laryngeal Biology Laboratory in Medical Center North. (photo by Mandy Whitley)

by Kelsey Herbers

Vanderbilt University Medical Center’s David Zealear, PhD, has received a $3.6 million grant from the National Institutes of Health (NIH) for a clinical trial to study the effectiveness of bilateral laryngeal pacing in treating patients with a bilaterally paralyzed larynx.

Over the next five years, 36 patients with a paralysis of both of their vocal folds will be randomized to one of two treatments: an implantable pulse generator (IPG) that electrically stimulates the muscles responsible for opening the vocal folds to restore the patient’s ability to breathe, or a repeated botulinum toxin (Botox) injection that will block regenerated nerves from unpredictably closing the vocal folds.

Often a life-threatening condition, bilateral paralysis of the larynx, which occurs due to damage to the nerves, prevents patients from opening their airway. Common causes for the condition include nerve injury due to neck or chest surgery involving the thyroid gland, esophagus, trachea or cervical spine.

While a tracheotomy — a surgical incision in the neck into the trachea to allow airflow — is an option for emergent intervention to restore adequate breathing, the most widely accepted treatment for chronic paralysis is a laryngeal cordotomy.

“Physicians make a laser lesion through the vocal fold so the patient can breathe through the mouth, which eliminates the need for a tracheotomy,” said Zealear, professor of Otolaryngology and principal investigator for the study. “But the problem is that you damage this beautiful, vibrating structure for speech and impair the voice. You also increase the possibility for aspiration during swallowing, which is a significant medical concern.”

While patients who receive a cordotomy don’t fully lose their ability to communicate, their voices become breathy and the artistic parts of their speech are affected. Patients who receive the procedure also struggle to breathe during exertion, reducing the possibility of maintaining an active lifestyle.

Recognizing the drawbacks of a cordotomy, surgeons at the Vanderbilt Voice Center also use botulinum toxin injections into the larynx to allow a wider space between the paralyzed vocal folds. While the temporary nature of the injections represents a significant improvement over a cordotomy, the injections only moderately improve ventilation and negatively affect voice and swallowing function. Patients must also regularly return to the clinic for repeated injections to prevent the vocal folds from closing.

Bilateral electrical stimulation of the muscles responsible for opening the vocal folds will allow the muscles to contract as they normally do, restoring a patient’s ability to breathe — including during physical activity — while also leaving their voice and swallowing function intact. The pacemaker device is implanted below the clavicle in the upper chest with its primary wires placed in pockets underneath the abductor muscles, which control the opening of the vocal folds.

Zealear, who first tested electrical stimulation of the larynx on patients with paralysis in only one vocal fold in 1996, says the results are remarkable.

“To have a patient for whom the expected outcome is simply to be able to ventilate and walk around rise to the level of engaging in strenuous activity is incredible,” said Zealear. “They’ll have a much more active lifestyle.”

The first patient to receive the treatment for bilateral laryngeal paralysis at VUMC was implanted in 2015 and has shown promising success over the last three years.

Zealear and his team, which includes James Netterville, MD, Gaelyn Garrett, MD, Maria Ellen Powell, PhD, Yike Li, MD, PhD, and Kate Von Wahlde, MJ, look forward to continuing their success rate through further recruitment.

“Vanderbilt is the nation’s leader in this type of translational research for vocal fold paralysis,” said Roland Eavey, MD, Guy M. Maness Professor and chair of Otolaryngology and director of the Vanderbilt Bill Wilkerson Center. “Dr. Zealear and our clinicians — Drs. Garrett and Netterville — have made a huge stride in the right direction, and we are excited to proceed in this trial to assist these deserving patients.”

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