Encephalitis

Suspect encephalitis whenever odd behavior, reduced consciousness, focal neurology, or seizures occur after an infectious prodrome (fever, rash, lymphadenopathy, cold sores, conjunctivitis, or meningeal signs). It is often wise to treat (see below) before the exact cause is known—usually viral, and often never identified.

If no prodrome is present, consider encephalopathy (e.g., hypoglycemia, hepatic encephalopathy, diabetic ketoacidosis, drugs, hypoxia, uremia, SLE, Wernicke's encephalopathy ( give vit B1 if in doubt ) ).

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Investigations:

1. Blood tests:

   • Blood cultures
   • Serum for viral PCR (also throat swab and midstream urine)
   • Toxoplasma IgM titre
   • Malaria film

2. Imaging:

   • Contrast-enhanced CT: Check for focal bilateral temporal lobe involvement (suggestive of HSV encephalitis) or meningeal enhancement (suggesting meningoencephalitis). Do before lumbar puncture (LP).
   • MRI is an alternative if allergic to contrast.

3. Lumbar Puncture (LP):

   • Increased CSF protein, lymphocytes, and decreased glucose (classic signs). Send CSF for viral PCR (including HSV).

4. EEG:

   • Urgent EEG showing diffuse abnormalities may help confirm encephalitis but won’t identify the cause.

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Management:

• Empirical Treatment:
  • Aciclovir (10 mg/kg every 8 hours IV over 1 hour) should be started within 30 minutes of arrival for suspected HSV encephalitis (14 days of treatment, extend to 21 days if immunosuppressed).
  • Specific therapies are available for CMV (combination therapy with ganciclovir and foscarnet as first line therapy) and toxoplasmosis (pyrimethamine + sulfadiazine + folic acid).
• Supportive Therapy:
  • Manage in ICU if required.
• Symptomatic Treatment:
  • Anticonvulsants (e.g., phenytoin) for seizures. (see Status epilepticus article)
• Prognosis:
  • Untreated viral encephalitis has a mortality rate of ~70%.

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