Neurosurgery notes/Infection/Cranial infection/Parasites/Protozoa/Amoebic infection

Amoebic infection

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Protozoa

Primary amoebic meningoencephalitis (PAM)

General

  • The only amoeba known to cause CNS infection in humans

Numbers

  • Rare (only 95 cases in the U.S. as of 2002, and ≈ 200 cases worldwide as of 2004).

Naegleria fowleri

  • The amoeba lives in fresh water and soil
  • PAM usually occurs within 5 days of exposure, usually from .
  • Diving in warm freshwater (Pond/Lakes) → Invading nasal olfactory mucosa. → Cribriform plate → CNS
    • Causes basilar haemorrhagic meningitis that may be rapidly fatal

Pathology

  • Diffuse encephalitis with haemorrhagic necrosis and purulent meningitis involving brain and spinal cord.
  • Destruction of the olfactory bulb and tract
  • Frontal and temporal lobe haemorrhage
notion image

Clinical presentation

  • Cerebral edema → increased ICP → herniation → Fatal in ≈ 95% of cases, usually within 1 week.

Evaluation

  • CSF: cloudy and often hemorrhagic, ⬆️ leukocytes, ⬆️ protein, normal or ⬇️ glucose, Gram stain negative (no bacteria or fungi), wet prep → motile trophozoites (may be confused with WBCs).

Treatment

  • Medical
    • Amphotericin B
      • Drug of choice
      • (Lipid preparations (Abelcet®) achieve higher MICs (minimal inhibitory concentrations) than other amphotericin preparations.
    • Miconazole
      • May be synergistic with amphotericin B.
  • Surgical intervention
    • Ventriculostomy with CSF drainage may be indicated when findings are suggestive of increased ICP.
    • In one survivor, surgical drainage of a brain abscess was performed in addition to treatment with a 6-week course of amphotericin B, rifampicin, and chloramphenicol (withdrawn from U.S. market).

Acanthamoeba

  • From contact lenses
  • Enters corneal stroma (treatment may require a corneal transplant),
  • Meningoencephalitis.

Entamoeba histolytica

  • Meningoencephalitis.