Encephalitis

Question 1

What is encephalitis?

Answer 1

Inflammation of brain parenchyma assoc w neurological dysfunction, such as altered state of consciousness, seizures, personality changes, CN palsies, speech problems, motor and sensory deficits.

Serious, complex and potentially fatal
Non-infectious and infectious causes

Question 2

Epidemiology of encephalitis?

Answer 2

Affects extremes of ages (under 1, over 65)

Question 3

Aetiology of encephalitis?

Answer 3

Aetiological agent only identified approx 50%

Bacterial, viral (most common), parasitic, fungal

Question 4

Viral causes of encephalitis?

Answer 4

• Herpes (HSV1, HSV2); most common
• Adenovirus
• Enterovirus
• Parechovirus

Question 5

Bacterial causes of encephalitis?

Answer 5

• Neisseria meningitidis
• TB
• Syphilis
• Listeria
• Lyme disease (bact), typhoid fever, etc

Question 6

Diagnostic criteria for encephalitis?

Answer 6

Major criterion needed:
- Altered mental state lasting 24h+ w no alternative cause identified

Minor criteria (2- possible encephalitis, 3- probable/ confirmed):
- Fever over 38C within 72h before or after presentation
- Generalised or partial seizures not fully explained
- New onset of focal neurological findings
- Cerebrospinal fluid WBC count over 5/mm3
- Neuroimaging abnormality of brain parenchyma
- EEG consistent with encephalitis

Question 7

Risk factors for encephalitis? (4)

Answer 7

• Insect bites
• Foreign travel
• Intravenous drug use (IVDU)
• Immunosuppression

Question 8

Signs and symptoms of encephalitis?

Answer 8

• Headache and fever
• Viral prodrome
• Raised ICP
• Meningism
• Level of consciousness (LOC) altered
• Altered GCS and mental state

Question 9

What are some symptoms of raised ICP?

Answer 9

Headache, blurred vision, feeling less alert, vomiting, changes in behaviour, weakness or problems w walking or speaking, sleepiness

Question 10

Ix: Investigations for encephalitis inclu?

Answer 10

Bloods, LP, EEG, brain CT/ MRI

Also: CXR routine for febrile work-up. Could detect cause, ie: TB, sarcoidosis

Question 11

Ix: What investigations and findings are there for bloods in encephalitis?

Answer 11

• High lymphocyes (FBC)
• Low sodium (SIADH) (Serum electrolytes)
• Blood cultures
• ESR/ CRP
• Viral serology

Question 12

Ix: What findings are there for LP in encephalitis?

Answer 12

• High lymphocytes
• Normal/ low glucose
• Viral PCR

Question 13

Initial management for encephalitis?

Answer 13

• ABCDE
• Acyclovir (give to all w suspected encephalitis and then give appropriate antiviral or AB according to underlying aetiology)

Question 14

Potential complications of encephalitis?

Answer 14

• Death
• SIADH
• Neuro sequelae: damage to the CNS resulting in cognitive, sensory, or motor deficits. May also manifest as emotional instability and seizures (most severe cases).