L38 Viral infections of CNS

Question 1

For acute meningitis, what are the causative viruses? (4)

Answer 1

1. Enterovirus
2. HSV-2
3. VZV
4. Parechovirus

Question 2

For acute encephalitis, what are the causative viruses? (5)

What are the type of encephalitis they cause respectively?

Answer 2

A. HSV-1, HSV-2,HHV6
- Focal encephalitis

B: Rabies, Japanese encephalitis virus
- Pan-encephalitis

Question 3

For acute myelitis (spinal cord), what are the causative viruses? (2)

Answer 3

1. Poliovirus

2. Enterovirus RV71, usually hand food mouth disease

Question 4

For acute tropical spastic paraparesis, what is the causative organism?

Answer 4

HTLV-1

• progressive demyelination of long motor neurone tracts in spinal cord

Question 5

What are the routes of CNS entry of virus?

Answer 5

1. Hematogenous
   - infected macrophages/lymphocytes as “Trojan horse”, e.g. JEV
2. Reactivation: from latency, e.g. herpesvirus
3. Neural: via peripheral nerve, e.g. rabies

Question 6

What is the definition of acute viral encephalitis?

Answer 6

Inflammation of the brain parenchyma

Question 7

Which has a more insidious symptoms? Meningitis or encephalitis?

Answer 7

encephalitis

Question 8

What is the most common cause for a viral encephalitis?
- sporadic, no seasonality

a) in neonates
b) in children and adults?

Answer 8

Herpes virus simplex

a) primary infection of HSV-2
b) reactivation of HSV-1

Question 9

Patient presents with low grade fever, confusion, seizures and dysphagia and has progressed to meningoencephalitis.

What are the investigations along the time line of 2 weeks?

Answer 9

1. D-0 Check neurological signs and symptoms
2. CSF for HSV PCR
3. D-7 MRI/CT scan /EEG
4. D-14 Intrathecal HSV antibody

Question 10

What is the most important thing to see in CSF in a patient with suspected encephalitis?

Answer 10

HSV PCR

since

• HSV Ab >10 days to develop
• Antigen detection and viral culture is insensitive (too few cells are present)

Question 11

What is the treatment for herpes simplex encephalitis?

What are the side effects of overdose of that drug? (2)

Answer 11

Acyclovir IV 10-15 mg/kg Q8h empirically until PCR result is available, for at least 3 weeks when confirmed

OD side effects (esp. in elderly)

1. Encephalopathy
2. Nephropathy: ensure adequate hydration

Question 12

Rabies virus is neurotrophic. List some the animal sources?

Answer 12

1. Dogs
2. Raccoons
3. Bats
   etc.

Question 13

Clinical features of rabies encephalitis?

o _________ period: depending on the site of wound bite; 2w – 3m, up to years
o Prodromal stage: _________, ___________ around the wound site
o Acute neurologic syndromes

Answer 13

Incubation;

fever, paraesthesia

Question 14

Name 2 acute neurological syndromes of rabies encephalitis.

Answer 14

1. Encephalitic: hydrophobia (fear of water due to throat muscle spasm during swallowing), photophobia, delirium
2. Paralytic: flaccid paralysis (fun fact: some are misdiagnosed as GBS)

Question 15

Rabies encephalitis is fatal. T/F?

Answer 15

True!

Coma > death due to cardio-respiratory arrest.

Question 16

Prevention of rabies encephalitis? (3)

Answer 16

1. Pre-exposure prophylaxis: inactivated rabies vaccine
2. Post-exposure prophylaxis: vaccine + rabies hyperimmune globulin (HRIG)
3. Veterinary measure: inactivated rabies vaccine to dogs/ cats

Question 17

What is hyperimmune globulin for post-exposure prophylaxis of rabies encephalitis?

Answer 17

Prepared from plasma of donors with high titre of antibody against an organism

Question 18

Name the acute viral myelitis you know.
What is the pathogenic pathway?
Presentation?

Answer 18

Poliomyelitis. (caused by poliovirus 1-3)

• direct infection of the anterior horn cells of the spinal cord
• fever, flaccid paralysis

Question 19

What is the vaccine given for poliovirus infection?

Answer 19

• inactivated vaccine

- oral live vaccine too

Question 20

Post-exposure syndrome of a viral infection:

• Immune-mediated disease as a result of infection/exposure to virus
• culprit virus may not be neurotrophic and virus cannot be isolated from CSF/brain tissue

Give 3 examples.

Answer 20

1. Post-infectious encephalomyelitis
2. Guillain-Barre syndrome
3. Reye’s syndrome

Question 21

_________________ occur during convalescent phase of certain viral infections or vaccination:
• Measles, mumps, rubella
• VZV
• Influenza

Answer 21

Post-infectious encephalomyelitis

Question 22

Post-infectious encephalomyelitis:

• ___________ caused : exposure to foreign Ag that closely resemble host proteins on tissues of brain & spinal cord > ____________
• CNS affected: permanent neurological deficits

Answer 22

Autoimmune;

widespread demyelination

Question 23

In GBS, what is the characteristic feature?
- Cause?

• no specific treatment, but resolve spontaneously over weeks-months.

Answer 23

Ascending paralysis - PNS affected, associated with parasthesia

• Occur days-weeks after acute phase of viral/ bacterial infection/ post-vaccination (rare)

Question 24

Reye’s syndrome is a post-infectious encephalopathy.
Associated with?

What are the common presentations? (2)

Answer 24

• Following viral infection (e.g. influenza, chicken pox), associated with use of aspirin
• Cerebral oedema, fatty liver

Question 25

Chronic viral infection of the CNS is rare.

What is the disease that issue to persistent measles infection in CNS?

Answer 25

Subacute-sclerosing panencephalitis (SSPE) *Sketchy!!

• measles virus remains and replicate in brain > damage
• slow, progressive degeneration of the brain over 6-8 years

Question 26

Progressive multifocal leukoencephalopathy (PML)
is the reactivation of ____________ virus in brain.

This viral infection is common, but only in _____________ causing neurological diseases.

Answer 26

JC virus

- AIDS and immunocompromised

Question 27

Subacute spongioform encephalopathy is related to _________disease?

Answer 27

Creutzfeldt-Jakob disease (Mad cow disease)