Encephalitis

Question 1

What is the definition of encephalitis?

Answer 1

Inflammation of the brain parenchyma

Question 2

What is the aietiology or risk factors involved with encephalitis?

Answer 2

• Most commonly due to VIRAL INFECTION

- Causes are viral, non-viral (RARE), immunocompromised and autoimmune/ paraneoplastic (due to cancer)

Question 3

What are the viral causes of encephalitis?

Answer 3

• Herpes Simplex Virus - MOST COMMON in the UK
• VZV
• Mumps
• Adenovirus
• Coxsackie
• EBV
• HIV
• Japanese encephalitis

Question 4

What are the non-viral causes of encephalitis?

Answer 4

• Syphilis

- Staphylococcus aureus

Question 5

What causes encephalitis in immunocompromised patients?

Answer 5

• CMV
• Toxoplasmosis
• Listeria

Question 6

What are the autoimmune / paraneoplastic causes of encephalitis?

Answer 6

Associated with certain antibodies (e.g. anti-NMDA, anti-VGKC)

Question 7

Epidemiology of encephalitis

Answer 7

UK incidence: 7.4/100,000

Question 8

What are the symptoms of encephalitis

Answer 8

Subacute onset (hours to days) 
Headache  
Fever  
Vomiting 
Neck stiffness  
Photophobia  
Behavioural changes  
Drowsiness  
Confusion  
History of seizures 
Focal neurological symptoms (e.g. dysphagia, hemiplegia) 

• In most cases, encephalitis is self-limiting and mild
• Important to obtain detailed travel history

Question 9

What are the signs of encephalitis upon physical examination

Answer 9

• Reduce consciousness
• Deteriorating GCS
• Seizures
• Pyrexia
• Signs of Meningism: (Neck stiffness, photophobia and Kernig’s test positive - Flex leg at knee hip and knee and complains of pain)
• Signs of raised ICP (Cushing’s Response: hypertension + bradycardia + irregular breathing and papilloedema)
• Focal neurological signs
• MMSE may show cognitive/ psychiatric disturbance

Question 10

What are the appropriate investigations for encephalitis?

Answer 10

• Bloods (FBC - high lymphocytes (indicates viral cause), U&Es - SIADH may occur as a result of encephalitis, Glucose, Viral serology and an ABG)
• MRI/CT (Important to exclude mass lesion and HSV can cause oedema of the temporal lobe on MRI)
• Lumbar puncture (High lymphocytes, High monocytes, High protein, Glucose is usually normal
  and a viral PCR is required)
• EEG - may show epileptiform activity
• Brain biopsy (rarely needed)