Encephalitis

Question 1

Encephalitis is

Answer 1

inflammation of the brain parenchyma.

It is mainly caused by viruses

other organisms include:

• some bacteria
• Mycoplasma
• Rickettsia
• Histoplasma

Suspect it when a viral prodrome is followed by;

• irrational behaviour
• altered conscious state
• possibly cranial nerve lesions.

Question 2

Clinical features

Answer 2

These can vary from mild to severe.

Constitutional:

• fever (not inevitable)
• malaise
• myalgia

Meningeal features:

• headache
• photophobia
• neck stiffness

Cerebral dysfunction:

• altered consciousness
• confusion
• drowsiness
• personality changes
• seizures

Focal neurological deficit

Question 3

Causes (viral organisms)

Answer 3

• Herpes simplex type 1 or 2, enteroviruses
• mump
• CMV
• EBV
• HIV
• measles
• influenza
• rabies
• arboviruses, e.g. Japanese B, West Nile, Murray Valley encephalitis, Ross River

Consider in the differential diagnosis;

• cerebral malaria
• Toxoplasma gondii in immunosuppressed esp. HIV

Question 4

Investigations

Answer 4

Lumbar puncture: CSF (usually aseptic meningitis)

CSF PCR for viral studies, esp. HSV, Toxoplasma gondii

CT scan—often shows cerebral oedema

Gadolinium enhanced MRI

EEG-characteristic waves

Question 5

Treatment

Answer 5

rganise hospitalisation where treatment will be supportive.

Suspected herpes simplex encephalitis should be treated with IV aciclovir immediately.

Question 6

Autoimmune encephalitis

Answer 6

Usually in young people:

• prodrome of fever and headache
• then days or weeks of psychiatric behavioural problems.

Diagnosis: antibodies (anti-NDMA).

Refer to consultant for specific immunotherapy.