Neurosurgery notes/Trauma/Primary head Injury/CSF leak

CSF leak

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Primary head Injury

Numbers

  • CSF leaks occur in approximately 2% of patients

Aetiology

  • Fractures involving
    • Frontal or ethmoidal sinuses
    • Petrous temporal bone

Investigations

Beta-2 transferin (ß2Tr)

  • General
    • A Tau protein
    • Molecule produced by neuraminidase activity within the brain.
    • Current gold standard test for confirming CSF leaks in patients with posttraumatic rhinorrhoea.
  • Numbers
    • Sensitivity (99%)
    • High Specificity (97%)
  • Location
    • Found in
      • CSF
        • Mainly
      • Not in nasal secretions.
      • Aqueous humour
      • Perilymph
      • Blood of patients with alcohol related chronic liver disease
  • Technique
    • A clotted blood sample and a sterile container containing the collected nasal or aural fluid are transported to a centralised laboratory for testing.
    • Takes 24 to 48 h to perform the assay and because of the qualitative nature of the test,
      • Expertise is needed to interpret the result.

Beta-trace protein (ßTP)

  • General
    • Second most common protein in the CSF after albumin,
    • Produced mainly by the epithelial cells lining the leptomeninges and by the choroid plexus.
  • Numbers
    • Accuracy: 95.7-97.4%
    • A negative predictive value of 97.1%
    • A positive predictive value of 100%
  • Function
    • Important for the maturation and maintenance of the central nervous system.
  • Location
    • Found in other bodily fluids,
      • Because its concentration in CSF is 32-35 times more than in plasma (14.6±4.6 mg/L in CSF and 0.46±0.13 mg/L in moderate variations of plasma ßTP (eg due to kidney injury) will not significantly affect results, and no control serum sample is need for the interpretation of the assay.
  • Advantages
    • Quantitative,
    • Less expensive than ß2Tr,
    • Takes under 15 mins to process.
  • Cons
    • Not suitable in patients with
      • Bacterial meningitis
      • Severely reduced glomerular filtration rates
    • When ßTP levels are in the range of 1.31 and 1.69mg/L because nasal secretions are known to contain similar levels of ßTP making ßTP in these ranges not diagnostic.

Management

  • Surgery
    • Aimed at reducing the symptoms and risk of infection in cases with persistent CSF leaks or fistulae.
    • Lumbar drainage
      • To relieve CSF pressure
      • Used for
        • Spontaneous repair
        • Surgical repairs
        • Facilitating a route to administer intrathecal fluorescein for diagnostic purposes
      • Risk of pneumocephalus and risk of intracranial infection
  • Antibiotic prophylaxis
    • No
  • Pneumovax
    • Types
      • Pneumococcal conjugate vaccine (PCV13)
      • Pneumococcal polysaccharide vaccine (PPSV23)
    • If sinuses are involved

Outcome

  • Majority of CSF leaks are self- limiting and resolve spontaneously within days
  • Infection rates between
    • 7% and 30% for TBI patients with CSF leaks, with each day of leakage increasing the risk of ascending intracranial infection