Encephalitis

Question 1

What is encephalitis?

Answer 1

Inflammation of the brain parencyma.
Can be:
- Infective: usually viral from haematogenous spread to the CNS. May also be bacterial, fungal or TB.

• non-infective e.g. autoimmune (NMDA-R, VGKC)

Question 2

How does encephalitis present?

Answer 2

1. personality change
2. headaches
3. seizures
4. reduced consciousness
5. visual disturbance
6. confusion
7. Fevers

Question 3

Which viruses cause encephalitis?

Answer 3

1. HSV-1 (most common)
2. Enterovirus
3. VZV
4. EBV
5. CMV
6. Rabies

Question 4

How would you diagnose encephalitis?

Answer 4

1. History and examination
2. Serology: CSF (PCR, cultures, gram stain and cell count, protein, glucose, cytology, autoantibodies), blood, sputum, FBC, clotting, LFTs, U&Es, TFTs, toxicology, B12 and folate, pregnancy test, HIV.
3. Radiology: CXR, CT head, MRI brain.
4. Others: EEG

Question 5

What are the differential diagnoses for encephalitis?

Answer 5

1. Infection - meningitis, HIV, cerebral abscess, sepsis
2. Vascular - infarction, haemorrhage, PRES
3. Malignancy - lymphoma, metastases.
4. Inflammation - vasculitis, autoimmune
5. Metabolic dysfunction - thyroid disease, steroids, low sodium, uraemia, hepatic encephalopathy.
6. Psychiatric disorders
7. Toxicology/overdose
8. NEAD

Question 6

How is infective encephalitis treated?

Answer 6

Typically aciclovir (10mg/kg TDS) for viral particularly HSV +/- cephalosporin (3rd gen) cover for bacterial.

Question 7

What is the prognosis of HSV encephalitis?

Answer 7

Treated HSV encephalitis has a mortality of around 10%. Untreated around 80%.
Complication rates are high in those who survive and can result in variable level of disability.

Question 8

How would your treatment differ in someone who is immunocompromised?

Answer 8

Assess for HIV infection and low threshold for covering CNS fungal infection.

Question 9

Describe the CSF findings in viral, bacterial, fungal and TB meningitis.

Answer 9

Viral: Clear colourless fluid, normal glucose, low protein, lymphocytosis,

Bacterial: turbid yellow/colourless fluid, low glucose, high protein, neutrophilia

Fungal: Turbid fluid, low glucose, high protein, fibrin web, lymphocytes

TB: Turbid fluid, low glucose, high protein, lymphocytes