What is posterior nares syndrome?

What is Posterior Nasal Drip Syndrome?

Posterior nasal drip syndrome, now preferably termed Upper Airway Cough Syndrome (UACS), is the drainage of secretions from the nose or paranasal sinuses into the pharynx, representing the most common cause of chronic cough in adults. 1, 2

Clinical Definition and Terminology

• The term "post nasal drip" has been replaced by "Upper Airway Cough Syndrome (UACS)" in current medical literature to more accurately reflect the condition's pathophysiology 1, 2
• UACS encompasses drainage from various rhinosinus conditions including allergic rhinitis, nonallergic rhinitis (vasomotor rhinitis), chronic sinusitis, and postinfectious states 1, 2

Cardinal Symptoms and Clinical Presentation

• The hallmark symptoms include sensation of drainage in the throat, frequent throat clearing, nasal discharge (anterior or posterior), and chronic cough 1, 2
• Physical examination may reveal cobblestone appearance of the oropharyngeal mucosa, which is a characteristic finding 2
• Approximately 20% of patients have "silent" UACS with no obvious postnasal drip symptoms yet still respond to treatment directed at the upper airway 1, 2

Underlying Etiologies

Allergic Rhinitis

• Characterized by seasonal or perennial symptoms with positive skin testing to specific allergens 1
• Associated symptoms include sneezing, watery rhinorrhea, nasal itching, and itchy watery eyes 1

Nonallergic Rhinitis (Vasomotor Rhinitis)

• Presents with excessive watery secretions triggered by odors, temperature changes, humidity changes, or eating (gustatory rhinitis) 1, 3
• Diagnosis is one of exclusion with negative allergy testing and no evidence of infection or structural abnormalities 1, 3

Nonallergic Rhinitis with Eosinophilia Syndrome (NARES)

• Characterized by perennial rhinitis symptoms with nasal eosinophilia (>20% eosinophils in nasal secretions) but negative allergy testing 1, 4, 5
• More frequent in females and may be associated with hyposmia and propensity toward nasal polyp development 4, 5
• May represent a precursor to aspirin-exacerbated respiratory disease 4

Chronic Rhinosinusitis

• Defined by presence of two or more symptoms (nasal blockage/obstruction, nasal discharge, facial pain/pressure, or reduced sense of smell) persisting ≥12 weeks 1
• May cause productive or nonproductive cough and can be "clinically silent" without typical acute sinusitis findings 1

Postinfectious UACS

• Develops following upper respiratory tract infection with persistent symptoms 1
• Typically responds to first-generation antihistamine/decongestant combinations 1, 2

Diagnostic Approach

• The diagnosis of UACS is primarily clinical and confirmed by successful response to treatment directed at the upper airway, not by symptoms or physical findings alone 1, 2
• Symptoms and clinical findings have low specificity (37-73% sensitivity) and are not reliable discriminators for establishing UACS as the cause of cough 2, 6
• Allergy testing (skin testing or in vitro testing) is required to distinguish allergic from nonallergic causes 1, 3
• Nasal endoscopy allows better visualization of posterior nasal cavity, nasopharynx, and sinus drainage pathways compared to anterior rhinoscopy 1
• CT imaging is not essential for UACS diagnosis but should be considered if chronic sinusitis is suspected and symptoms persist despite appropriate medical treatment 1, 6, 7

Treatment Principles

• First-generation antihistamine/decongestant combinations are the most effective first-line treatment for UACS, with older-generation antihistamines being superior to newer non-sedating antihistamines due to their anticholinergic properties 2
• Specific effective combinations include dexbrompheniramine maleate plus sustained-release pseudoephedrine sulfate, or azatadine maleate plus sustained-release pseudoephedrine sulfate 2
• Most patients experience improvement within days to 2 weeks of initiating therapy 2
• For allergic rhinitis-related UACS, intranasal corticosteroids (fluticasone 100-200 mcg daily) should be added for a 1-month trial 2
• Ipratropium bromide nasal spray is an alternative for patients who cannot tolerate or have contraindications to antihistamine/decongestant combinations 2

Critical Clinical Pitfalls

• Failure to consider "silent" UACS (without obvious postnasal drip symptoms) can lead to missed diagnoses in up to 20% of cases 1, 2
• Newer-generation antihistamines are ineffective for non-allergic causes of UACS and should not be used as first-line therapy 2
• UACS frequently coexists with other causes of chronic cough (asthma, gastroesophageal reflux disease), requiring sequential evaluation if symptoms persist despite adequate upper airway treatment for 2 weeks 2
• Decongestants can worsen hypertension, cause tachycardia, insomnia, and increased intraocular pressure in glaucoma patients, requiring careful monitoring 2