Encephalitis

Question 1

What is encephalitis?

Answer 1

Infection/inflammation of the brain parenchyma

Question 2

What are the types/causes of encephalitis?

Answer 2

Viral encephalitis

• Most common
• Usually Herpes simplex (HSV) ​
  
  • other than in neonates - nearly always HSV type 1
• Others - VSV, arbovirus (overseas travel?)

Autoimmune encephalitis

• Anti-VGKC
• Anti-NMDA receptor
• Paraneoplastic limbic encephalitis

Other less common causes/types are:

• Malignancy - Metastatic, paraneoplastic^
• Metabolic
• Post seizure
• Migraine

Question 3

How does viral encephalitis present?

Answer 3

Flu-like prodrome (4-10 days)

Progressive headache associated with fever:

• ± meningism
• Progressive cerebral dysfunction
• Seizures
• Focal symptoms/signs

Question 4

Risk factors for viral encephalitis?

Answer 4

Overseas travel

• Arbovirus is caught from mosquitoes, ticks etc so thats a risk factor

Question 5

How would you differentiate Bacterial meningitis from viral encephalitis?

Answer 5

Viral encephalitis has a slower onset (4-10 days of flu symptoms) and has more prominent cerebral dysfunction (confusion, memory problems etc)

Bacterial meningitis may also have petechial rash if meningococcal

Question 6

What symptoms/signs are specific to Anti-VGKC (Voltage Gated Potassium Channel)?

Answer 6

Frequent seizures

Amnesia (cant retain new memories)

Altered mental state

Question 7

What signs/symptoms are specific to Anti-NMDA receptor encephalitis?

Answer 7

Flue like prodrome

Prominent psychiatric features

Altered mental state and seizures

Progressing to a movement disorder and coma

Question 8

How is encephalitis investigated?

Answer 8

Bloods

• cultures, FBC, U&Es, clotting, septic screen

CT brain ± MRI

• MRI will show areas of inflammation, swelling + any coning

Lumbar puncture

• elevated lymphocytic levels CSF
• If viral encephalitis - PCR analysis
  
  • Lab diagnosis by PCR of CSF for viral DNA

​EEG

Question 9

How is Viral encephalitis treated?

Answer 9

Suspected HSV & VSV encephalitis:

• treat immediately with IV aciclovir - even before investigation results are available

If seizures - treat with anticonvulsants

If coning - decompressive craniectomy

Question 10

Risk factors for Paraneoplastic limbic encephalitis (PLE)

Answer 10

H/o Cancer - especially Lung & testicular cancer