Chronic Cough

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Please note that the following is a general guideline/ discussion only. For a full assessment, exclusion of any other underlying cause for your symptoms and an individualised treatment approach, you will need to be seen by a qualified specialist.

Definition
Cough is a conserved physiological reflex designed to protect the airway from violation by inhaled or aspirated material. 

Chronic cough: Cough more than 8 weeks can be difficult to treat 

Prevalence 

Cough is the most common presenting symptom to ambulatory medical practice visits in the US, 
Chronic cough is estimated between 10-30 % of adults 

Aetiology

Historically Reported
Gastric Reflux, Asthma and post Nasal drip has been documented as a cause around 90%
All the above are highly prevalent disorders hence may have an incidental association


Current Theories

A Silent Laryngeal Reflux: 

The likely Hypothesis are
1) micro aspiration of acid
2) inflammation due to acid sensitising the vagus nerve
3) Oesophageal pressure receptor stimulation: Volume reflux (whether acid or non-acid) may result in abnormal oesophageal contractions possibly providing a cough stimulus. Therefore even non acid reflux may still cause cough.



B Post Nasal Drip
There is no strong evidence that post nasal drip causes cough
However there is some evidence to suggest that treating post nasal drip may improve cough. This association is more noticeable if there is evidence of sinusitis with bacterial biofilms. Currently it appears reasonable to treat those who have a post nasal drip medically. Surgery Should be reserved to patients who have an additional indication due to chronic sino-nasal symptoms, not responding to medical treatment (not cough alone).


Vagal Neuropathy
Various irritants and stimulants of the vagus nerve may lead to sensitisation of the larynx. Some likely causes are silent laryngeal reflux, a viral infection and allergy. Once the vagus nerve is sensitised cough may easily be precipitated by minimum stimuli such as cold air. 

Treatment of the initiating event will not improve symptoms. Instead neuromodulating medications such as baclofen, amitriptyline, gabapentin and pregabalin. Use of these are limited by side effects hence reserved to those who do not respond to other treatments. There is evidence that speech therapy may help, especially if there is paradoxical vocal cord movement noted during ENT-endoscopy. 




Management.

Look at Possible Medications
Medications such as ACE inhibitors should be stopped.

Treat Pulmonary Causes
Exclude a possible pulmonary cause such as asthma, Bronchitis. 
CXR, Spirometry or further investigations should be done.
Response should be Monitored

Mindful of Other Causes
Being mindful of disorders affecting swallowing, chronic laryngeal infection, systemic inflammatory conditions such as Wegner's or sarcoidosis. Relevant work up should be done if any suggestion of any sinister cause.




Assessment of Post Nasal Drip, Larygo-pharynx and Voice
After Exclusion of the above work up for post nasal drip, silent laryngeal reflux.

Trans-nasal endoscopy: This will give a view of the nasal space and the post nasal space and the laryngo-pharynx. This is done by all ENT surgeons in the clinic.

Transnasal oesophagoscopy: Gives a full length view of the oesophagus, done by a limited number of laryngologists.

After assessment,Maximum Medical treatment of possible silent laryngeal reflux and post nasal drip.

Non responders: Need complete endoscopy with PH monitoring and Manometry. This is to review the degree of acid as well as non acid reflux. Preferably done by a general surgeon, who has the capability of surgical treatment.




Surgery
Those who have evidence of a post nasal drip, with other significant, recalcitrant sino-nasal symptoms will benefit from surgery

Those who have severe reflux may benefit from Nissen Fundoplication