Encephalitis

Question 1

Define encephalitis

Answer 1

Infection and inflammation of the brain parenchyma. Broad term with various causative agents.

Question 2

What is the epidemiology and risk factors for encephalitis?

Answer 2

• Around 2500 cases in England per year
• Extremes of age - particularly HSV-1 which is usually more severe
• Immunocompromisation

Question 3

What causes encephalitis the most?

Answer 3

Viruses

Question 4

Which virus causes encephalitis in 95% of cases?

Answer 4

HSV-1

Question 5

What are other viruses that cause encephalitis?

Answer 5

VZV, EBV, CMV, HIV, measles, mumps, arboviruses (West Nile)

Question 6

What is a non-viral cause of encephalitis?

Answer 6

Toxoplasmosis (close contact with cats, parasitic infection)

Question 7

Describe the pathophysiology of encephalitis

Answer 7

• An intracranial infection provokes an inflammatory response causing inflammation of the cortex, white matter, basal ganglia and brain stem depending on the causative organism
• This results in neurological signs and systemic signs of infection
• The frontal and temporal lobes are mostly affected

Question 8

What are the symptoms of encephalitis?

Answer 8

Classic triad of:
- Fever
- Headache
- Encephalopathy/altered mental status/focal neurological signs (Insidious onset, can also be abrupt)

Question 9

Describe other symptoms that may be present

Answer 9

• Features of a viral infection to begin with - fever, malaise, nausea, headaches
• Behavioural change - common early sign
• Decreased consciousness, confusion
• Focal neuro signs - cranial nerve palsies, hemiparesis, cerebellar ataxia, dysphagia, dysarthria
• Seizures
• Signs of raised ICP may lead to coma

Question 10

What is a sign that shows the temporal lobe is affected?

Answer 10

Aphasia

Question 11

What might it suggest if the symptoms are like in meningism?

Answer 11

Meningo-encephalitis

Question 12

What are some differential diagnosis for encephalitis?

Answer 12

Anything that causes behavioural change
eg.
- DKA
- Hypoglycaemia
- Stroke
etc

Question 13

What do you do for investigations for encephalitis?

Answer 13

• MRI head
• Lumbar puncture
• EEG (electroencephalogram)

Question 14

What is seen on MRI for encephalitis?

Answer 14

• Shows swelling and inflammation (HSV typically affects temporal lobes), may show signs of raised ICP
• Unilateral usually temporal encephalitis

Question 15

What is seen on EEG for encephalitis?

Answer 15

• May indicate encephalitis (periodic sharp followed by slow waves)
• Non specific firing of 2H2 periodically

Question 16

What is seen on lumbar puncture for encephalitis?

Answer 16

• Shows elevated lymphocytes
• normal glucose
• typically a raised protein

Question 17

What is the treatment of encephalitis?

Answer 17

• Suspected encephalitis - empirically start IV Acyclovir until results
• HSV or VZV - Immediate IV Acyclovir (Ganciclovir can be used in VZV)

Question 18

What is the treatment of encephalitis in immunocompromised patients?

Answer 18

use combination antiviral therapy

Question 19

What would you use to treat seizures in encephalitis?

Answer 19

anticonvulsants e.g., Primidone