Study Could Lead to Better Diagnosis and Treatment of Diseases Affecting the Larynx
In a first-of-its-kind study, Mount Sinai researchers have used sensory mapping to discover that the posterior part of the larynx (closest to the swallowing tract) is the main area of the voice box to protect the airway from potentially dangerous swallowed or inhaled substances. This novel finding can potentially help doctors better understand and manage diseases affecting the larynx and lead to new, targeted treatments. The results of this study have been published in the June online edition of The Laryngoscope.
"The human voice box ('larynx') is arguably one of the most life-sustaining organs in the body, yet there is still much we don't know about its basic functions. This study sheds light on a critical protective function of the larynx that we have not had definite proof of until now," explained author Catherine Sinclair, MD, FRACS, Assistant Professor of Otolaryngology at the Icahn School of Medicine at Mount Sinai. "Understanding this aspect of basic larynx physiology is essential to help us diagnose laryngeal disease, manage it appropriately, and create new therapies."
Dr. Sinclair, along with Sedat Ulkatan, MD, Director of Intraoperative Neurophysiology at Mount Sinai West, and Maria Tellez, MD, Neurophysiologist at Mount Sinai West, started this research to find out if different areas of the human larynx had different abilities to elicit a protective airway reflex termed the "laryngeal adductor reflex" (LAR), which is an involuntary protective response to stimuli in the larynx. This is important because many conditions affecting the larynx, including cancer, reflux, laryngomalacia ('soft larynx' in infancy), and laryngospasm (uncontrolled contraction of the larynx), likely impair or over activate our ability to elicit the LAR, which in turn can impair airway protection, putting patients at increased risk of aspiration and pneumonia.
Researchers analyzed 10 patients while under general anesthesia. All had normal laryngeal function. The team used a probe to deliver a low-intensity electric stimulus to different areas of the larynx and recorded whenever this stimulus was able to elicit the LAR and cause vocal cord contraction. They discovered that stimulation of the back part of the larynx produced vocal cord contraction in all patients. No other areas of the larynx produced consistent results. This proved that the back of the larynx is a highly sensitive area and the one to most easily elicit the LAR. Before this study, it was widely known that if patients had the back part of their voice box removed or affected by certain diseases, they had a more difficult time protecting their airway. The research showed at a physiological level why that is the case. Researchers also found that the vocal folds themselves do not elicit a reflex to low-intensity stimulations.
"This knowledge is essential to facilitate our accurate diagnosis and treatment of a variety of upper-airway diseases. These results will allow us to refine existing and develop new techniques for the diagnosis of diseases such as aspiration, dysphagia, and laryngospasm," said Dr. Sinclair. "The study results may also give us insight into unexplainable diseases including sudden infant death syndrome (SIDS). We hope to use the results of this study to develop new diagnostic tests for laryngeal diseases."
"This study will help to transform our current understanding of the protective function of the larynx, conceivably opening new exploration opportunities in various human respiratory disorders such as SIDS and patients with high risk of aspiration undergoing general anesthesia," said Dr. Ulkatan. "We will be able to explore new diagnostic tests and possibly some therapeutic neuromodulation due to the new groundbreaking physiologic principles uncovered in this research," added Dr. Tellez.