Encephalitis

Question 1

Define encephalitis.

Answer 1

Encephalitis is defined as inflammation of the brain parenchyma associated with neurological dysfunction such as altered state of consciousness, seizures, personality changes, cranial nerve palsies, speech problems, and motor and sensory deficits.

Question 2

Explain the aetiology of encephalitis.

Answer 2

It is the result of direct inflammation of the brain tissue, as opposed to the inflammation of the meninges (meningitis), and can be the result of infectious or noninfectious causes. An aetiological agent is only identified in around 50% of cases.

Question 3

Explain the risk factors of encephalitis.

Answer 3

Age <1 or >65 years
Immunodeficiency
Post-infection
Blood/body fluid exposure
Organ transplantation
Animal or insect bites
Location
Season
Swimming or diving in warm freshwater or nasal/sinus irrigation

Question 4

Summarise the epidemiology of encephalitis.

Answer 4

Around 2500 cases of encephalitis occur in England each year. Globally, the incidence of encephalitis is around 7 per 100,000 population per year. There is no specific gender predominance, but frequently a bimodal age distribution is seen with highest incidence in those under one year and over 65 years.

Question 5

Recognise the presenting symptoms of encephalitis. Recognise the signs of encephalitis on physical examination.

Answer 5

Fever
Rash
Altered mental state
Focal neurological deficit
Meningismus
Cough
Gastrointestinal infection

Question 6

Identify appropriate investigations for encephalitis and interpret the results.

Answer 6

FBC
Peripheral blood smear
Serum electrolytes
LFTs
Blood cultures
Throat swab
Nasopharyngeal aspirate
Sputum culture
Chest radiography
CT brain
MRI brain
EEG
CSF analysis
CSF culture
CSF serology
CSF polymerase chain reaction (PCR)