UCSF researchers have developed a first-of-its-kind technique to objectively evaluate laryngopharyngeal sensation. This could be transformative for patients suffering from laryngopharyngeal disorders, as it makes it possible to assess for deficits in sensation and determine the safety of swallowing.
Promising for patient safety
“This kind of test has never been done before,” said UCSF’s Clark A. Rosen, MD, chief of the Division of Laryngology and co-director of the UCSF Voice and Swallowing Center. “We’re hoping to unlock some unknown mechanisms of disorders of the larynx to determine if they are sensory related. The test has the potential to be a monitoring device for safety of swallowing. Sensory deficits are a problem for people who are trying to swallow because if you can’t feel something in your throat and it goes down the wrong way, you can aspirate and die.”
Proof-of-concept and validation testing
This novel clinical test assesses quantitative sensory function of laryngopharyngeal structures using an aesthesiometer known as Cheung-Bearelly monofilaments, named in part for UCSF otologist-neurotologist Steven Cheung, MD, who developed the test and conducted the initial study with other researchers. Cheung and the team compared patients who had been treated with radiation therapy with a healthy control group. To measure the participants’ oral tactile sensory thresholds, the researchers tested four locations – the anterior tongue, buccal mucosa, posterior tongue and soft palate – using different sizes of Cheung-Bearelly monofilaments. The researchers found the group treated with radiation therapy required higher force to detect the stimuli at all four locations.
Since the initial study, UCSF researchers have performed validation testing of the technique and established a normal range for all age groups.
In one study, Rosen, Cheung and other researchers tested healthy adults using 6-0, 5-0 and 4-0 Cheung-Bearelly monofilaments on the aryepiglottic fold, lateral pyriform sinus and medial pyriform sinus. The outcomes measured were the laryngeal adductor reflex (LAR) and the patient-reported rating of perceptual strength.
Rates of triggered LAR increased monotonically as tactile force increased. The aryepiglottic fold and medial pyriform sinus were the most responsive and the lateral pyriform sinus the least. No statistically significant differences were found between men and women. The research suggests that LAR response profiles to low- and high-force stimuli may be used as screening tools to diagnose laryngopharyngeal hypersensitivity conditions like cough and globus sensation and hyposensitivity conditions such as dysphagia.
In another study, healthy adults were tested for LAR response using 5-0 and 4-0 Cheung-Bearelly monofilaments on the aryepiglottic fold and medial pyriform sinus. The UCSF team found that a positive LAR response to 5-0 or 4-0 monofilament stimulation could be expected in over 90% of asymptomatic adults. A negative LAR response to 4-0 monofilament stimulation identified patients at risk for laryngopharyngeal hyposensitivity.
In a recent paper, UCSF researchers described their work studying LAR response latency profiles in healthy adults from tactile stimulation of the aryepiglottic folds and medial pyriform sinuses using 4-0 and 5-0 Cheung-Bearelly monofilaments. The team’s goal was to assess LAR integrity beyond simply determining the presence or absence of a triggered reflex. They found the combined mean value of LAR latency was 176.6 milliseconds without significant difference between the locations or forces. The researchers noted that variations in LAR response latency between stimulation forces or laryngopharyngeal subsites may help to identify mechanisms of upper aerodigestive tract disorders.
Applications and clinical trials
This novel test has the potential to evaluate if a physical sensory abnormality contributes to a number of laryngopharyngeal conditions. The UCSF Voice and Swallowing Center began a clinical trial in May of 2021 using the technique to evaluate laryngopharyngeal sensation in patients with adductor spasmodic dysphonia.
“For the first time ever, we have the ability to measure sensation in swallowing-disordered patients,” Rosen said. “We hope this will guide our recommendations on who can safely eat and who cannot, for example. It also has the potential to be a monitoring device for head and neck cancer patients going through radiation treatments. This is prime for a whole new area of investigation, and we have multiple phases to our research agenda.”
To learn more
UCSF Voice and Swallowing Center
Phone: (415) 885-7700 | Fax: (415) 885-7800