Your department performs – among other interventions - laryngeal reinnervation surgery. How does this technique work?
Müller: The cause of a paresis is a disturbed nerve function, which interrupts the nerve impulses to the laryngeal muscles that move the vocal folds. The reinnervation approach uses an alternative nerve from the vicinity of the larynx, one that otherwise serves other small muscles in the throat and whose loss is tolerable. We move it toward the larynx, ensuring the nerve increases stimulation in the muscles. This gives the denervated muscle fibers more volume and tension again. While this does not move the vocal cords, it still provides the necessary tension to support good and clear vibrations on the opposite side to produce sound – similar to a stringed instrument.
Another more complex procedure is selective laryngeal reinnervation. Here, various nerves are repositioned to the larynx. They open the vocal folds in a synchronized breathing movement and close again when sound is produced. This process partially restores the normal mobility of the larynx. However, these surgeries are very complex and take between six to eight hours. They are not a good option for patients with comorbidities and have so far only been performed in a few centers around the world for bilateral paralysis, not for unilateral vocal cord paralysis.
You are involved in studies that test a laryngeal pacemaker system for treatment of bilateral vocal fold paralysis. How does this device work?
Müller: The approach resembles the workings of a heart pacemaker: the application of electrical stimulation is designed to open both vocal folds in patients, allowing better breathing. You must remember that even though nerves damaged in bilateral vocal fold paralysis usually grow back together, their function is lost because the proper connection to the target muscle remains disrupted. While the brain controls both the opening and closing of the larynx, the contraction of the muscles is no longer coordinated. However, since there is still a neuromuscular connection, the laryngeal pacemaker system aims to stimulate the target muscle directly behind the site of the nerve injury. This triggers the vocal folds to open.
The idea of laryngeal pacing has been around since the late 1970s. We collaborated with the Austrian company Med-El Elektromedizinische Geräte GmbH to expand on the concept and use selective neural stimulation to activate the target muscle. In a first study between 2012 and 2014, we successfully tested the laryngeal pacemaker system on seven patients in Gera, Würzburg, and Innsbruck. After some further enhancements, centers in Germany and Austria will launch additional studies this spring. We aim to show that the stimulation can improve the opening of the vocal folds and reduce or even eliminate the symptoms of patients. What makes the technology we plan to test in studies so innovative is that this does not require open surgery on the larynx as this is a minimally invasive method where we introduce the electrodes directly into the target muscle for stimulation. This prevents any subsequent damage to the larynx.
Which patients are good candidates for this treatment?
Müller: We identify patients in pre-examination procedures. This allows us to determine whether the patient has a sufficient neuromuscular junction that responds to an electrical impulse and opens the vocal folds.
What is the timeline for these studies?
Müller: The studies will take about one to two years and are subsequently analyzed. Depending on the results, the goal is to get medical device approval for the pacemaker, both in Europe and around the world. It is meant to be a new treatment option for bilateral vocal cord paralysis.
