THE CASE
A 60-year-old man with a past medical history of gastroesophageal reflux disease (GERD) and dyslipidemia presented to his family physician for evaluation of chronic cough. Five years prior, the patient had developed a high fever and respiratory symptoms, including a cough, and was believed to have had severe otitis media. He was treated with multiple courses of antibiotics and corticosteroids for persistent otitis media. Although the condition eventually resolved, his cough continued.
The persistent cough prompted the patient to consult a succession of specialists. First, he saw a gastroenterologist; following an esophagogastroduodenoscopy, he was prescribed pantoprazole. Despite the proton-pump inhibitor (PPI) therapy, the cough remained. Next, he had multiple visits with an otolaryngologist but that yielded no specific diagnosis for the cough. He also saw an allergist-immunologist, who identified a ragweed allergy, gave him a diagnosis of cough-variant asthma, and prescribed antihistamines and mometasone furoate and formoterol fumarate dihydrate. Neither was helpful.
After 5 years of frustration, the patient complained to his family physician that he still had a cough and “a tickle” in his throat that was worsened by speaking and drinking cold beverages. He denied fever, shortness of breath, nausea, vomiting, or any other associated symptoms.
THE DIAGNOSIS
The failed treatment attempts with antihistamines, corticosteroids, bronchodilators, and PPI therapy excluded multiple etiologies for the cough. The throat discomfort and feeling of a “tickle” prompted us to consider a nerve-related disorder on the differential. The diagnosis of laryngeal sensory neuropathy (LSN) was considered.
DISCUSSION
LSN is a relatively uncommon cause of chronic refractory cough that can also manifest with throat discomfort, dysphagia, and dysphonia.1 It is thought to result from some type of insult to the recurrent laryngeal nerve or superior laryngeal nerve via viral infections, metabolic changes, or mechanical trauma, leading to a change in the firing threshold.2 The hypothesis of nerve damage is supported by the increased incidence of LSN in patients with goiters and those with type 2 diabetes.3,4 When there is a decrease in the laryngeal sensory threshold, dysfunctional laryngeal behavior results, leading to symptoms such as persistent cough and throat clearing.
Diagnosis. LSN is often diagnosed clinically, after GERD, allergies, asthma, angiotensin-converting enzyme inhibitor intake, and psychogenic disorders have been ruled out.1 Our patient had a prior diagnosis or investigation of nearly all of these conditions. Other clues pointing to an LSN diagnosis include a cough lasting 8 weeks or more, recurrent sensory disturbances (such as a tickle) of instantaneous onset before each cough episode, triggers that can include talking or a change in air temperature, daily coughing episodes numbering in the 10s to 100s, and a nonproductive cough.5,6
Beyond clinical clues, laryngeal electromyography, which evaluates the neuromuscular system in the larynx by recording action potentials generated in the laryngeal muscles during contraction, can be used for diagnosis.4 Videostroboscopy, which allows for an enlarged and slow motion view of the vocal cords, can also be used.
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