An 82 year old woman presents with fever, seizures and a history of anorexia, diarrhoea and vomiting.

List three (3) clinical features which would indicate the need for a brain CT scan prior to lumbar puncture in this patient?

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College Answer

1. New onset seizures
2. Immunocompromised state
3. Moderate to severe impaired level of consciousness
4. Focal neurological signs (signs suspicious of a space occupying lesion)

Discussion

The question is really asking, "what are the features of increased intracranial pressure in the presence of a space-occupying lesion?"

  • Hypertension and bradycardia
  • Focal neurological signs
  • Decreased level of consciousness
  • No previous history of epilepsy
  • Predisposition to infection (eg. immunocompromised state)
  • Papilloedema
  • History of stroke or intracranial space-occupying lesion

Clinical features of increased intracranial pressure, specifically referring to patients with meningitis, are discussed elsewehere. The References section below contains a single article on this topic, well worth reading. The most important feature of it - Tabel 2 - is reproduced below to simplify revision.

Who Should Undergo a Head CT prior to LP?

Immunocompromised host

  • HIV or AIDS
  • On immunosuppressant drugs, including steroids
  • Post transplant (any sort of transplant)
  • Post-splenectomy patients, particularly when under-immunised.

History of focal CNS disease

  • Known tumour
  • Known stroke
  • Known focal infection

New onset of seizures

  • Within 1 week of presentation

Ongoing or recent seizures

  • Prolonged seizures
  • Within 30 minutes of the last seizure

(Seizures in general seem to cause an increase in intracranial pressure, in the absence of a space-occupying lesion, and with a deceptively normal head CT.)

Papilloedema

  • Normal venous pulsations suggest a normal ICP

Decreased level of consciousness

  • Irrespective of focal neurology (or the desire to do an LP) this finding alone would probably make the head CT mandatory.

Focal neurological signs

  • Dilated unreactive pupil
  • Cranial nerve signs
  • Unilateral weakness
  • Partial seziures
 

References

References

 

Tunkel, Allan R., et al. "Practice guidelines for the management of bacterial meningitis." Clinical infectious diseases 39.9 (2004): 1267-1284.