Treating Chronic Refractory Cough with Superior Laryngeal Nerve Block
The treatment is simple and effective for many patients, but more research is needed to determine the exit-strategy from repetitive injections.
Coughing is one of the more common complaints that brings a patient to the doctor. Chronic refractory cough is a cough that persists for more than two months, the onset is sometimes associated with upper respiratory infection and coughing fits can be set off by environmental exposures. This usually results in the patient pursuing multidisciplinary evaluation, including pulmonology, gastroenterology and allergy specialists. At Cleveland Clinic, pulmonary and otolaryngology tend to be the final common pathways for patients, and superior laryngeal nerve block (SLN) may be an option for patients when medical management and cough suppression therapy do not provide patients the relief they seek.
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“We try to take a fresh look when patients come see us,” explains Paul C. Bryson, MD, MBA, the director of the Cleveland Clinic Voice Center and Section Head of Laryngology in Cleveland Clinic’s Head & Neck Institute. “Sometimes we make sure they’re not on any medications that cause a chronic cough, and we reevaluate their workup. Neuromodulators — gabapentin, amitriptyline and tramadol —can be used in an off-label way to control chronic cough. So for patients that don’t tolerate or respond to any of those medicines, the nerve block is something that we started to perform over the past few years to try to help our most non-responsive patients.”
The treatment involves just a small injection where the superior laryngeal nerve lies between the thyroid cartilage and the hyoid bone. The injections involve triamcinolone with or without lidocaine. Dr. Bryson notes that when he started performing the procedure, he used both medications; however, some of his patients would experience numbness for several hours following the uncomfortable injection, so he uses almost exclusively steroids now.
Regarding the procedure, says Dr. Bryson, “I will find the thyrohyoid space and the superior laryngeal nerve region. I use my thumb and forefinger to feel those two structures. The injection is not very painful for patients. Patients will typically feel some pressure, and they might feel some pressure that radiates to the ear. This sensation usually dissipates over about an hour or less. The procedure itself takes less than 10 minutes.”
While the SLN block itself is fairly simple, Dr. Bryson notes that there is a lack of understanding and consensus about the process for weaning the patient off serial injections. The nerve block lasts for only a short amount of time before the efficacy begins to decline. “The available research suggests about one to three months.”
After three months following the patient’s injection, Dr. Bryson may bring the patient in for another round of treatment as long as the injections remain efficacious. Since it’s a steroid, the patient’s response is tracked, and Dr. Bryson says they have seen a few patients that get frequent injections who experience some skin fragility and bruising. If the patient starts to develop those symptoms, he may delay injecting to see if the symptoms subside.
Dr. Bryson, Michael Benninger MD and Candace Hrelec, MD, presented their experience at the 2021 Fall Voice Conference. Over the past few years, they have treated 87 patients with SLN blockade and have seen a positive response rate. “Out of this group of 87 patients, we had 78.8% who reported some improvement and 18 had no improvement. On average, people reported about a 57% improvement in their baseline cough,” says Dr. Bryson. “We have to see how well sustained it is, but I suspect it’s a real number of people that get benefit from it. I would like to be able to provide better data on de-escalation of treatment, because that would imply that perhaps we have allowed an opportunity for a “reset” the cough reflux, but we do not have the data for that conclusion at this time.”