The Mystery Chronic Cough (a.k.a. habit cough, tic cough, psychogenic cough, irritable larynx syndrome)
There are patients with a mysterious chronic dry cough (longer than 6 months) that seems to defy all explanation and resist all the usual standard treatments. Some of these patients have coughed for more than ten years resulting in frustration not only in terms of treatment, but diagnosis. Often, patients are told their cough is due to reflux, allergy, asthma, infection, aspiration, virus, etc and undergo numerous exams and studies including pulmonary function tests, chest x-rays, reflux studies, barium swallows, upper endoscopy, CT scans, MRI scans, etc. Even all medications known to cause a cough as a side effect (ie, statins, ACE Inhibitors and Angiotensin Receptor Blockers) are removed to no avail. More often than not, all these medical studies come back normal. Furthermore, proposed treatments with antibiotics, proton pump inhibitors, allergy medications, cough suppressants, steroid inhalers, etc are not successful. Surgery may even be performed which also fails to improve the cough. Eventually, some are even told it's all in their head (psychogenic cough, habit cough, tic cough, etc) or idiopathic.
A typical patient with the chronic cough is described as follows:
- Started during or after recovering from a viral laryngitis and/or upper respiratory infection
- Dry cough
- Cough occurs due to no perceivable reason...perhaps only a tickle
- Cough may occur several times an hour to even as often as several times a minute. Must be distinguished from whooping cough (severe attacks of a choking cough that lasts 1-2 minutes often with near vomiting and appearance of suffocation. Watch Mayo Clinic video).
- Cough does not seem to get better with time (months or even years)
- All diagnostic studies performed come back normal
- Endoscopy of the throat and voicebox is normal (this exam will be performed on the first visit to ensure that there is no anatomic reason for the cough). Such anatomic factors that may trigger a cough include an elongated uvula as well as large tonsils (Link #1 • Link #2 • Link #3 • Link #4)
If this description sounds like you, you may have chronic cough due to laryngeal sensory neuropathy (aka, sensory neuropathic cough, vagal neuropathy, etc). What does this mean? Essentially, this means that the nerve that provides sensation to the voicebox and is responsible for triggering the cough reflex has been injured, usually by a virus. When this happens, the nerve's level of sensitivity before it triggers the cough reflex becomes markedly reduced; in other words, it becomes hyper-sensitive. This situation is akin to the elevated sensitivity of the skin producing pain even with the lightest touch after healing from a bad burn, even if the skin appears completely normal. Other related forms of such sensory neuropathy include diabetic neuropathy, post-herpetic neuralgia, phantom limb pain, etc.
Normally, the nerve recovers its normal level of sensitivity and the cough resolves. However, in some patients, the nerve does not recover and a persistent chronic cough results. In this scenario, the best medications are those that "calm" the nerve down. Such medications include amitriptyline (elavil), nortriptyline (pamelor, aventyl), tramadol (Ultram), desipramine, pregabalin (lyrica), or gabapentin (neurontin). Read NYT article.
If you are well-versed in medications, you will realize that these are the same medications used to treat various peripheral neuropathies listed in the prior paragraph. Please note that for a given patient, one medication may work better than the other which may not work at all. Trial and error is unfortunately necessary. Also, these medications will NOT help a cough due to an active infection (cold, flu, pneumonia, bronchitis, etc). See references below in how these meds should be taken.
With careful guidance with these medications, the cough signficantly improves and even completely resolves. The medications are taken for 3 to 6+ months after which it is slowly tapered down. Of note, in certain rare situations, vocal cord dysfunction, globus pharyngeus, and chronic throat-clearing are related disorders treated in a similar manner (once reflux and other medical disorders are ruled-out or thoroughly managed).
Patients need to keep in mind that it is not unusual that a patient may have SEVERAL factors of cough as well, all of which need to be treated in order to resolve a persistent cough. For example, reflux and allergies may be present as well as laryngeal sensory neuropathy. Because this disorder results in a hypersensitized larynx, problems with reflux and allergies which ordinarily would not cause a cough in normal patients, will now cause a persistent cough. In other words, though allergy testing may reveal only mild allergies and 24 hour pH impedance study may show reflux episodes within normal range, these "mild" problems now need to be treated aggressively along with the neuropathy. The lack of treatment for each and every known cause of cough (even if mild) is the most common reason why treatment of laryngeal sensory neuropathy fails with neuropathic medication. To reiterate... laryngeal sensory neuropathy is a hypersensitized larynx. In this hypersensitized state, even a little bit of reflux or allergies will trigger a cough which normally would not. Each and every one of these conditions need to be treated. Read more about this scenario here.
Finally, it is becoming recognized that voice therapy (under guidance from a qualified speech language pathologist or SLP) is beneficial for patients with neurogenic chronic cough. Through self-awareness exercises and therapy, patients are often able to decrease laryngeal sensory hyper-responsiveness leading to cough decrease. The SLP therapy program has several components that include behavior modification, cough suppression behaviour, and vocal hygiene training. This treatment should be differentiated from voluntary cough suppression which does not appear to be helpful. For more info, see references below. You can read about one behavior modificaton program that can be tried at home here.
In extremely rare situations, botox injections into the vocal cords may help should the medications be found ineffective. In other rare situations, a superior laryngeal nerve block using a percutanous injection of a local anesthetic mixed with a steroid has also been helpful to decrease nerve sensitivity overall. Watch a video to see how a superior laryngeal nerve block is performed.
Of note... If it is a child with a chronic cough, there is a VERY rare disorder called PANDAS (Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus) where strep infections can trigger motor tics including chronic cough (or throat clearing) seemingly overnight. If there is concern for this particular disorder, an evaluation with a pediatric neurologist may be warranted. Here is a link to a girl who sneezed constantly due to this disorder. Here is a New York Times article.
If you are a musician playing a wind or brass instrument... your chronic cough could be due to your instrument! Germs have been found inside such instruments that can get inhaled into your lungs causing a pneumonitis resulting in chronic cough. Read more about this here.
Finally, in extraordinarily rare situations, the cough is due to brainstem vascular nerve compression of the vagus nerve root... a type of syndrome known as VANCOUVER Syndrome (Vagus Associated Neurogenic Cough Occurring Due to Unilateral Vascular Encroachment of Its Root). You can read a case report here.
These records are
- Bordetella serum titres
- SELSAP Study (Surface Evoked Laryngeal Sensory Action Potential)
- GI Workup
- Esophagoscopy (Evaluate for esophageal pathology. In rare cases, mucosal ulcers have been found hypothesized to irritate the recurrent laryngeal nerve, found alongside the esophagus, resulting in cough). Watch video.
- Barium swallow (Evaluate for esophageal motility problems as well as Zenker's diverticulum). Watch video on this test.
- 24-Hour Multichannel Intraluminal Impedance (MII) and pH monitoring with manometry (Evaluate for acid as well as non-acid reflux). Watch video on how this is performed. Please note that BRAVO and other types of pH studies are NOT good enough.
- Response after maximum reflux medication treatment
- A rapid spit test (PepTest or PepsinCheck) can be performed to determine if reflux is present as well.
- Allergy Workup
- CT Sinus scan (Evaluate for subclinical chronic sinusitis)
- Allergy testing (Evaluate for allergies). If positive, allergy injection response report
- Pulmonary Workup
- Pulmonary function test with methacholine challenge (Evaluate for reactive airway disease)
- FeNO (Fraction of Exhaled Nitric Oxide) (Another measure for reactive airway disease)
- Bronchoscopy with lavage cultures (Evaluate for subclinical pulmonary infections/masses/reactive airway disease)
- CT Chest scan (Evaluate for lung masses too small to be seen on Chest X-ray)
- Response to asthma medications
- Treatment of chronic neurogenic cough with in-office superior laryngeal nerve block. Laryngoscope. 2018 Apr 18. doi: 10.1002/lary.27201. [Epub ahead of print]. Link
- Treatment of Neurogenic Cough with Tramadol: A Pilot Study. Otolaryngol Head Neck Surg. 2017 Jul;157(1):77-79. doi: 10.1177/0194599817703949. Epub 2017 May 2. Link
- Long-term follow-up of amitriptyline treatment for idiopathic cough. Laryngoscope. 2016 May 25. doi: 10.1002/lary.25978. [Epub ahead of print] Link
- Amitriptyline for symptomatic treatment of idiopathic chronic laryngeal irritability. Ann Otol Rhinol Laryngol. 2013 Jan;122(1):20-4. Link
- Use of specific neuromodulators in the treatment of chronic, idiopathic cough: a systematic review. Otolaryngol Head Neck Surg. 2013 Mar;148(3):374-82. doi: 10.1177/0194599812471817. Epub 2013 Jan 8. Link
- Gabapentin for refractory chronic cough: a randomised, double-blind, placebo-controlled trial. The Lancet. Aug 28, 2012. doi:10.1016/S0140-6736(12)60776-4. Link
- Management of Recurrent Laryngeal Sensory Neuropathic Symptoms. Norris BK, Schweinfurth JM. Ann Otol Rhinol Laryngol. 2010; 119:188-191. Link
- Chronic cough as a sign of laryngeal sensory neuropathy: diagnosis and treatment. Lee B, Woo P. Ann Otol Rhinol Laryngol. 2005 Apr;114(4):253-7. Link
- Gabapentin in the Treatment of Intractable Idiopathic Chronic Cough. Mintz S, Lee JK. Am J Med. 2006; 119(5):e13-15. Link
- Laryngeal Neuropathy as a Cause of Chronic Intractable Cough. Mishriki YY. Am J Med. 2006; 119(5):e5. Link
- Sensory neuropathic cough: a common and treatable cause of chronic cough. Bastian RW, Vaidya AM, Delsupehe KG. Otolaryngol Head Neck Surg. 2006 Jul;135(1):17-21. Link
- Effectiveness of amitriptyline versus cough suppressants in the treatment of chronic cough resulting from postviral vagal neuropathy. 2006. Jeyakumar A, Brickman TM, Haben M. Laryngoscope 116(12):2108-2112. Link
- The irritable larynx syndrome. Morrison M, Rammage L, Emami AJ. Journal of Voice. 1999;13:447-55. Link
- Vagal neuropathy after upper respiratory infection: a viral etiology? Amin MR, Kaufman JA. American Journal of Otolaryngology, 2001;22(4):251-256. Link
- Cough and paradoxical vocal fold motion. Altman KW, Simpson CB, Amin MR. Otolaryngology-Head & Neck Surgery. 2002;127(6):501-11. Link
- Botulinum Toxin A: A novel adjunct treatment for debilitating habit cough in children. Sipp JA, Haver KE, Masek BJ, Hartnick CJ. ENT Journal 2007;86(9):570-572. Link
- Use of botulinum toxin type A for chronic cough: a neuropathic model. Archives of Otolaryngology-Head & Neck Surgery. 2010;136(5):447-452. Link
- A new treatment option for laryngeal sensory neuropathy. Halum SL, Sycamore DL, McRae BR. Laryngoscope. 2009. Link
- Postviral vagal neuropathy. Rees CJ, Henderson AH, Belafsky PC. Annals Otol Laryngol Rhinol. 118(4):247-52, 2009. Link
- Cough reflex sensitivity improves with speech language pathology management of refractory chronic cough. Cough (London, England), 6, 5. http://doi.org/10.1186/1745-9974-6-5. Link
- Efficacy of speech pathology management for chronic cough: a randomised placebo controlled trial of treatment efficacy. Thorax. 2006; 61(12): 1065–1069. Link
- Chronic Cough : A tutorial for speech-language pathologists. Journal of medical speech-language pathology, Vol. 15, no.3, 2007, pp. 189-206
- Speech pathology for chronic cough: a new approach. Pulm Pharmacol Ther. 2009 Apr;22(2):159-62. doi: 10.1016/j.pupt.2008.11.005. Epub 2008 Nov 21. Link
- Review series: chronic cough: behaviour modification therapies for chronic cough. Chron Respir Dis. 2007;4(2):89-97. Link
- Chronic cough and laryngeal dysfunction improve with specific treatment of cough and paradoxical vocal fold movement. Cough. 2009 Mar 17;5:4. doi: 10.1186/1745-9974-5-4. Link
- The role of voice therapy in the management of paradoxical vocal fold motion, chronic cough, and laryngospasm. Otolaryngol Clin North Am. 2010 Feb;43(1):73-83, viii-ix. doi: 10.1016/j.otc.2009.11.004. Link
- The Relationship Between Chronic Cough and Paradoxical Vocal Fold Movement: A Review of the Literature. Journal of Voice 20: 3, 466-480 (2006) Link
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