Encephalitis

Question 1

Define encephalitits

Answer 1

inflammation of the brain parenchyma

Question 2

Explain the aetiology/risk factors of encephalitis

Answer 2

• Most commonly due to VIRAL INFECTION

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

• Non-Viral (RARE)
○ Syphilis
○ Staphylococcus aureus

• In immunocompromised patients
○ CMV
○ Toxoplasmosis
○ Listeria

• Autoimmune or Paraneoplastic
○ Associated with certain antibodies (e.g. anti-NMDA, anti-VGKC)

Question 3

Summarise the epidemiology of encephalitis

Answer 3

• UK incidence: 7.4/100,000

affects the very young and very old

Question 4

Recognise the presenting symptoms of encephalitis

Answer 4

• In most cases, encephalitis is self-limiting and mild
• 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)
• Obtain a detailed TRAVEL HISTORY

Question 5

Recognise the signs of encephalitis on physical examination

Answer 5

• Reduce consciousness
• Deteriorating GCS
• Seizures
• Pyrexia

• Signs of Meningism (meninges inflammation):
○ Neck stiffness
○ Photophobia
○ KERNIG’s test positive

Signs of raised ICP:
○ Cushing’s Response: hypertension + bradycardia + irregular breathing
○ Papilloedema

• Focal neurological signs - ataxia, clumsiness
- perhaps abnormal reflexes
• MMSE may reveal cognitive/psychiatric disturbance

Question 6

Identify appropriate investigations for encephalitis

Answer 6

• Bloods
○ FBC - high lymphocytes (indicates viral cause)
○ U&Es - SIADH may occur as a result of encephalitis
○ Glucose
○ Viral serology
○ ABG

• MRI/CT
○ Exclude mass lesion
○ HSV causes oedema of the temporal lobe on MRI

• Lumbar Puncture
○ High lymphocytes
○ High monocytes
○ High protein
○ Glucose is usually normal

-Viral PCR
• EEG - may show epileptiform activity
• Brain biopsy (rarely needed)

Question 7

What causes the most sever type of encephalitis?

Answer 7

Herpes simplex virus

Question 8

What is parenchyma?

What is brain parenchyma?

Answer 8

Parenchyma is the bulk of any tissue.

Brain parenchyma is brain tissue, which is mainly composed of neurones and glial cells.