Cerebrospinal fluid (CSF) vs Nasal discharge – Differences

Watery discharge from the nose can occur in cases of CSF rhinorrhoea and allergic rhinitis (also in other causes of increased mucus secretion in nose). It is important to differentiate between them so that appropriate treatment can be given.

  • History
    • CSF rhinorrhoea – head injury, surgical procedures, intracranial tumours
    • Allergic rhinitis – sneezing, head cold, itching, lacrimation
  • When the discharge occurs
    • CSF rhinorrhoea – when straining or bending forward
    • Allergic rhinitis – no relation to straining or bending forward, continuous flow
  • Whether discharge can be sniffed back
    • CSF rhinorrhoea – cannot be sniffed back
    • Allergic rhinitis – can be sniffed back
  • Character of discharge
    • CSF rhinorrhoea – clear, thin, watery
    • Allergic rhinitis – slimy (mucus), watery (tears)
  • Taste
    • CSF rhinorrhoea – sweet
    • Allergic rhinitis – salty
  • Glucose levels
    • CSF rhinorrhoea – more than 30mg/dl. Should be compared to the levels in CSF obtained after lumbar puncture as glucose levels decrease in intracranial infections)
    • Allergic rhinitis – less than 10mg/dl
  • Specific test – Beta 2 transferrin
    • CSF rhinorrhoea – invariably present
    • Allergic rhinitis – absent
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