Encephalitis

Question 1

eDefine encephalitis

Answer 1

Encephalitis is a severe, acute inflammation of the brain parenchyma

Question 2

Explain the aetiology/risk factors for echephalitis

Answer 2

• Human Herpresviruses are the main cause of encephalitis, with HERPES SIMPLEX VIRUS 1 being the most common group of viruses identified.
• Arbovirus is the most common cause worldwide
• Viruses can reach the CNS via haematogenous spread but HSV specifically use retrograde axonal transport where they travel from the skin to a sensory ganglion and eventually to the CNS
• Other causes:
  
  • Autoimmune
  • Toxoplasmosis (in HIV)
  • TB
  • N. meningitidis (meningo-encephalitis)
  • Listeria, Lyme disease, Malaria

RISK FACTORS:

• Age <1 or > 65 (extremes of age)
• Immunodeficiency
• Post-infection (e.g. EBV)

Patient with previous measles infection:
* Sub-sclerosing pan encephalitis

Patient with HIV on monoclonals
* Progressive multifocal leukoencephalopathy

Question 3

Recognise the presenting symptoms of encephalitis

Answer 3

This is a SEVERE ACUTE INFECTION

• Fever
• Headache
• Rash
• CNS Manifestations:
  
  • Altered mental state/confusion
  • Focal neurological deficits
    
    • UMN signs,
    • hemiparesis,
    • hemanopia,
    • CN deficits
  • Amnesia (affects temporal lobes)
  • Personality changes
  • Seizures

Question 4

Recognise the signs of encephalitis on physical examination

Answer 4

• Fever
• Confusion
• Focal neurolougical deficits (neuro exam)

Question 5

Identify appropriate investigations for encephalitis and interpret the results

Answer 5

• LUMBAR PUNCTURE for CSF analysis:
  
  • Clear/cloudy
  • Elevated lymphocytes
  • Normal glucose
  • High/Normal proteins
  • High/normal RBC
• CSF PCR for HSV
• CT shows temporal lobe changes in HSV encephalitis
• FBC: Lymphocytosis