Encephalitis

Question 1

Define Encephalitis

Answer 1

Inflammation of the Brain parenchyma

Question 2

List the causes of Encephalitis

Answer 2

Most commonly due to Viral infection

• Viral Causes: HSV (most common in UK), VZV, Mumps, Adenovirus, Coxsackie, EBV, HIV, Japanese encephalitis
• Non-viral: (Rare) Syphilis, Staphylococcus
• In immunocompromised patients: CMV, toxoplasmosis, listeria
• Autoimmune or paraneoplastic: associated with certain antibodies (e.g. anti-NMDA, anti-VGJC)

Question 3

What is the epidemiology of encephalitis?

Answer 3

UK incidence = 7.4/100,000

Question 4

What are the presenting symptoms of encephalitis?

Answer 4

• In most cases encephalitis is self-limiting and mild
• Subacute onset (hours - days)
• Headache
• Fever
• Vomiting
• Neck stiffness
• Photophobia
• Behavioural changes
• Drowsiness
• Confusion
• History of seizures
• Focal neurological symptoms (e.g. dysphagia, hemiplegia)
• Obtain a detailed travel history

Question 5

What are the signs of Encephalitis?

Answer 5

• Reduced consciousness
• Deteriorating GCS
• Seizures
• Pyrexia
• Signs of Meningism: Neck sitffness, photophobia, Kernig’s test positive
• Signs of raised ICP: Cushing’s response = hypertension + bradycardia + irregular breathing, Papilloedema
• Focal neurological signs
• MMSE may reveal cognitive/psychiatric disturbance

Question 6

What are the appropriate investigations for Encephalitis?

Answer 6

Bloods:
- FBC - high lymphocytes indicates viral disease
- U&Es SIADH may occur as a result
- Glucos
- Viral serology
- ABG
MRI/CT:
-  Exclude mass lesion
- HSV causes oedema in the temporal lobe on MRI
Lumbar Puncture:
- High lymphocytes
- High monocytes
- High protein
- Glucose is usually normal
- Viral PCR
Brain Biopsy (rarely needed