Encephalitis

Question 1

What is encephalitis?

Answer 1

histological diagnosis characterised by inflammation of the encephalon (or brain parenchyma)

Question 2

How many cases of encephalitis occur in England each year?

Answer 2

2500

Question 3

What is the age distribution of encephalitis?

Answer 3

bimodal: highest incidence in those <1 year and >65 years

Question 4

What are 8 clinical features of encephalitis?

Answer 4

1. Altered mental status
2. Fever
3. Headache
4. Psychiatric symptoms
5. Flu-like prodromal illness
6. Early seizures
7. Vomiting
8. Focal features e.g. aphasia

Question 5

Is there a link between peripheral lesions (e.g. cold sores) and the presene of HSV encephalitis?

Answer 5

no

Question 6

What is the commonest cause of encephalitis and in what proportion of patients is this?

Answer 6

Herpes simplex 1 (95%)

Question 7

What are 7 viral cause sof encephalitis?

Answer 7

1. Herpes simplex virus type 1
2. Herpes simplex virus type 2
3. Cytomegalovirus
4. Epstein Bar virus
5. Varicella Zoster virus
6. HIV
7. Arboviruses (including West Nile virus)

Question 8

What are 4 bacterial pathogens that can cause encephalitis?

Answer 8

1. Meningitis-causing bacteria e.g. meningococcus, pneumococcus
2. Lyme disease
3. Mycoplasma
4. Severe Falciparum malaria

Question 9

What is another type of encephalitis cause in addition to viral and bacterial?

Answer 9

autoimmune encephalitis including NMDA-receptor antibody associated encephalitis

Question 10

How does encephalopathy differ from encephalitis?

Answer 10

encephaopathy refers to generalised disease of the brain not attributable to inflammation (e.g. hypoglycaemia, hepatic, DKA, drug-induced, uraemic, SLE, hypoxic, beriberi)

Question 11

When should encephalitis be suspected?

Answer 11

any patient with sudden onset behavioural change, new seizures and unexplained acute headache with meningism

Question 12

What are 5 investigations to perform in suspected encephalitis?

Answer 12

1. Blood tests: routine, blood cultures, viral PCR for HSV
2. CSF - send for viral PCR
3. Imaging: CT, MRI better
4. Malaria blood film
5. EEG

Question 13

What will CSF show in encephalitis?

Answer 13

lymphocytosis, elevated protein

Question 14

What additional test should be performed on CSF in suspected encephalitis?

Answer 14

viral PCR

Question 15

What is CT likely to show in encephalitis?

Answer 15

medial temporal and inferior frontal changes e.g. bilateral multifocal petechial haemorrhages

Question 16

What imaging modality is best in encephalitis?

Answer 16

MRI

Question 17

In what proportion of patients with encephalitis is the CT normal?

Answer 17

one third

Question 18

What is the typical EEG pattern in encephalitis?

Answer 18

lateralised periodic discharges at 2 Hz

Question 19

What is the treatment of encephalitis?

Answer 19

• broad spectrum antibiotics: 2g IV ceftriaxone BD
• 10mg/kg aciclovir IV TDS for 2 weeks

Question 20

What can supportive management of encephalitis involve?

Answer 20

prompt termination of seizure activity with anticonvulsants (such as phenytoin)

Question 21

What are 7 side effects of aciclovir?

Answer 21

1. generalised fatigue/malaise (common)
2. GI disturbance (common)
3. Photosensitivity and urticarial rash (common)
4. acute renal failure
5. haematological abnormalities
6. hepatitis
7. neurological reactions