chronic cough

Introduction

Cough lasting >3 weeks (>8 weeks) without an obvious cause.

Etiology

• allergic rhinitis*, postnasal drip (most common cause)
• bronchospasm, asthma*
• gastroesophageal reflux*
• COPD
• postinfectious cough (generally viral infection or Mycoplasma)
• pharmaceutical agents:
  • ACE inhibitors (20% of patients given ACE inhibitor)
  • beta-blockers
• connective tissue diseases
  • temporal arteritis
  • rheumatoid bronchiolitis
  • Sjogren's syndrome
• infectious: Bordetella pertussis (whooping cough)
• eosinophilic bronchitis
• habit cough
• unlikely etiologies
  • obstructive sleep apnea
  • tonsillar enlargement & recurrent tonsillitis
  • external ear disease mediated through auricular branch of the vagus nerve
  • parenchymal lung disease not visible on chest X-ray
    • pulmonary fibrosis
    • bronchiectasis
    • sarcoidosis
  • tracheobronchial disease
    • tracheobronchomalacia
    • chronic bronchitis
    • tracheopathia osteochondroplastica
  • foreign body inhalation (may be radiolucent)
  • Whipple's disease (rare)

* 3 most common causes (90%); 99% in non-smokers with normal chest X-ray, not taking an ACE inhibitor

Epidemiology

• 12% of general population
• more common in women than men
• most common in 5th & 6th decade of life

Pathology

• cough reflex hyperresponsiveness

Clinical manifestations

• cough & other symptoms associated with etiology
  • cough with exercise or colde exposure suggests cough-variant asthma
• presence of other symptoms (edema, arthralgias, myalgias, night sweats, diarrhea, headache) suggest a systemic etiology
• can persist for years

Laboratory

• sputum eosinophils to rule out eosinophilic bronchitis
  • after spirometry & failed treatment for asthma

Diagnostic procedures

• ear, nose & throat examination
• spirometry if obstructive lung disease (asthma, COPD) suspected or failure of intranasal glucocorticoids
  • even if GERD more likely diagnosis (GRS11)
• Bernstein test or ambulatory esophageal pH testing
  • trial of proton pump ihibitor indicated prior to testing
• methacholine inhalation challenge to exclude asthma
• bronchoscopy in the absence of chest X-ray abnormalities is of low diagnostic yield with exceptions
  • case of Christmas tree needle inhalation in child apparent only with laryngoscopy
  • eosinophils on bronchial wash for non-asthmatic eosinophilic bronchitis

Radiology

• chest X-ray, especially for smokers
• high-resolution CT of thorax for refractory cases

Complications

• physical, social, & psychological effects

Management

• empiric therapy recommended prior to extensive workup
  • gabapentin may be useful
• for postnasal drip
  • antihistamines
  • decongestants
  • glucocorticoid nasal spay, flunisolide, fluticasone ...
• post-infection not caused by postnasal drip: ipratropium nasal spray
• for cough variant asthma & post viral infection, treat as asthma
• for GERD, use proton pump inhibitor for at least 8-12 weeks
  • acid suppression with proton-pump inhibitors not effective in treating chronic cough due to GERD
• for non-asthmatic eosinophilic bronchitis, treat empirically with inhaled glucocorticoid
• referral for diagnostic testing only after failure of empiric therapy
• idiopathic chronic cough
  • antitussive: dextromethorphan
  • topical anesthetic: benzonatate
  • low-dose morphine
  • gabapentin or pregabalin
  • multimodal speech therapy (treatment of choice)

More general terms

• cough
• chronic respiratory tract disease

More specific terms

• habit cough; somatic cough syndrome; psychogenic cough; cough tic