Using botox to treat vocal cord paralysis
in patients with MS
By Marc Iskowitz
DOCTORS FROM THE UNIVERSITY of Michigan Medical Center in Ann Arbor have extended the use of botulinum toxin (Botox) to a new area of vocal cord dysfunction. Eugene Rontal, MD, and Michael Rontal, MD, found that Botox can be used to restore complete mobility of the vocal cords and improve voice in a patient with vocal cord paralysis associated with multiple sclerosis (MS) (Journal of Voice, in press).
These results were seen after just one injection, reported Dr. Eugene Rontal, clinical professor of otolaryngology at the University of Michigan Medical School. Repeated shots were not necessary.
"It appears to work fairly well," he said, but "it's new and needs to be corroborated."
The two investigators remobilized the vocal cord using a technique they developed called "laryngeal rebalancing," in which Botox is selectively injected into certain intrinsic laryngeal muscles to "splint" the arytenoid, allowing the cartilage to heal in the proper position. This approach is an "extension of the use of Botox into other areas of vocal cord disease," Dr. Rontal said.
The two researchers pioneered the use of Botox to reposition the arytenoid cartilage in cases of acute anteromedial arytenoid dislocation (The Laryngoscope, Vol. 109).
The new application of Botox became possible after other researchers made strides in the treatment of vocal fold paralysis, including the ability to accurately examine the larynx with electromyography (EMG) and to electively paralyze some laryngeal muscles and leave others intact.
Dr. Rontal pointed out that the recent case study was an unusual one. He had never before seen a patient with MS and vocal fold paralysis.
MS is a patchy demyelinization of nerves in the brain and spinal cord that affects the cranial nerves. It is associated with aphonia, dysarthria and diplophonia.
The patient, 43, presented with MS and a breathy voice, which she had for more than four years.
The researchers diagnosed her vocal fold paralysis using a combination of electromyographic readings, computed tomography (CT) scanning, and clinical findings.
The EMG recordings showed evidence of some voluntary electrical activity in the muscles of the membranous vocal fold on the immobile side and evidence of recruitment indicating innervation. The CT scan revealed anteromedial displacement of the arytenoid cartilage.
Clinical findings pointed to an anteromedial displaced arytenoid with a bowed and foreshortened vocal cord. Arytenoid dislocation may stem from either a fixed cord due to joint involvement or from a paralyzed cord secondary to nerve disruption. Treatment differs for each etiology.
At first Dr. Rontal thought the patient had a fixed cord, but the vocal cords did not respond to treatment for this problem.
"That's when I believed this may be a paralysis rather than a fixation," he said.
He could not make a definitive diagnosis because the EMG was inconclusive. These tracings can be hard to interpret since a paralyzed cord can have voluntary motor units.
"A paralyzed vocal cord does not have the same electrical activity as one fixed because of scarring or dislocation," Dr. Rontal said. "Initially, the electrical activity led us to believe it was a subluxated arytenoid when it was probably synkinesis or mild regeneration of the nerve fiber--not enough to make the vocal cord move, but enough to show some electrical activity."
Although a paralyzed vocal cord is fixed from nerve disruption, it can demonstrate involuntary motor activity 75 percent of the time, according to Dr. Rontal. Synkinesis occurs when the recurrent laryngeal nerve, in its attempt to restore itself, sends sprouts of neural tissue into the voice box. However, the neural tissue does not go to the right muscle, resulting in spastic vocal cord action.
Reinnervation often occurs in both sets of laryngeal muscles, the adductors and abductors. If the abductors--the muscles that tend to pull the vocal cord away from the midline--are weakened with Botox, the adductor fibers may pull the vocal cord back to the midline of the airway and restore a good voice.
By taking advantage of existing reinnervation in the cord and utilizing functioning muscles from the opposite side of the displacement, the researchers remobilized the patient's vocal cord.
They derived a procedure to weaken or unbalance the distractive forces of the intrinsic laryngeal musculature with Botox. After making a diagnosis, they examined the larynx while the patient was under general anesthesia. They pushed the arytenoid in a posterolateral direction to a position on top of the cricoid cartilage and then injected the Botox, using a dose similar to that used for individual muscle group injection in the treatment of spasmodic dysphonia.
The injection consisted of two and a half units each into the thyroarytenoid muscle and lateral cricoarytenoid muscle on the affected side.
The Botox had its desired effect, weakening the adductor muscles and allowing the abductors to function unopposed. In this way the rebalancing technique enabled the arytenoid cartilage to reposition itself correctly on the cricoid.
In cases of arytenoid subluxation, there is evidence of a flaccid vocal fold, and the arytenoid usually is tilted forward (The Larynx and Its Diseases, Philadelphia: Saunders and Co., 1937).
"The cricoarytenoid joint is kind of flimsy," Dr. Rontal observed. However, once returned to its normal position, the cricoid joint will stay in position and heal until the patient has a normal voice.
Follow-up, completed at weekly intervals, revealed some motion in the cord one week after surgery. A month after the procedure, the patient's voice quality completely returned to normal as confirmed by objective speech analysis, including voice spectrography and perturbation analysis.
There were no complications related to the procedure, and just one injection was needed to restore total vocal cord mobility.
"She's been fine for two years now," Dr. Rontal observed.
Since treating this patient, he has had success with the laryngeal rebalancing technique in patients with vocal fold paralysis stemming from metastatic chest cancer and lesions of the recurrent laryngeal nerve, with idiopathic vocal cord paralysis, and with a recurrent laryngeal nerve traumatized from an accident or surgery.
Botox should be used selectively and only when patients have a fixed cord, when there is electromyographic evidence of paralysis or fixation, and when the clinical appearance indicates a displaced arytenoid and fixed vocal cord.
The arytenoid displacement becomes apparent when the arytenoid is anteromedially displaced and the cord is paralyzed.
Dr. Rontal urged speech-language pathologists who notice these symptoms to contact an otolaryngologist to corroborate the diagnosis. After surgery he frequently consults with speech-language pathologists to help patients improve their vocal range further through exercises.
For more information, contact Eugene Rontal, MD, at the University of Michigan Medical School, 28500 Orchard Lake Rd., Ste. 200, Farmington Hills, MI 48334; (248) 737-4030.
Marc Iskowitz is associate editor of ADVANCE.