Viruses affecting the CNS

Question 1

What is a neurotropic virus

Answer 1

capable of replicating in nerve cells

Question 2

What is a neuroinvasive virus?

Answer 2

capable of entering or infection the CNS

Question 3

What is a neurovirulent virus?

Answer 3

a virus capable of causing disease anywhere within the nervous system

Question 4

What viruses enter the CNS via the olfactory bulb?

Answer 4

coronavirus, herpes simplex virus)

Question 5

What viruses enter the CNS via the blood stream

Answer 5

poliovirus, mumps virus, measles virus, coxsackievirus; also HIV in monocytes

Question 6

Where do viruses affecting the nervous system replicate?

Answer 6

Cell body (uses host machinery -> site of protein synthesis)

Question 7

Why aren’t viruses travelling in nerve axons removed by the immune system?

Answer 7

nerve cells do not have class 1 molecules -> Tc cells cannot attack

Question 8

What viruses travel via axon fibres of the PNS to the CNS?

Answer 8

Rabies virus, yellow fever virus, HSV1&2

Question 9

What is sub-acute sclerosis panencephalitis?

Answer 9

late sequalae to measles infection -> causes chronic demyelination and dementia

Question 10

What is Reye’s syndrome? what is it associated with

Answer 10

occurs post infection with influenzaV or chickenpox in children, resulting in cerebral oedema -> associated with aspirin use for initial fever

Question 11

What is Guillane-Barre syndrome?

Answer 11

acute inflam demyelinating disease following infection with EBV, CMV, HIV. Results in partial/total paralysis that recovers

Question 12

What is postinfectious encephalomyelitis? how does it occur?

Answer 12

occurs a few days post measles/chickenpox, rubella or mumps. No virus but inflammation and demyelination -> possibly autoimmune

Question 13

What are the most common causes of viral encephalitis?

Answer 13

HSV1&2, rabiesvirus, arboviruses, enteroviruses

Question 14

what is encephalitis

Answer 14

inflam of brain

Question 15

Rabies virus has high neuro what?

Answer 15

neuroinvasiveness and neurovirulence

Question 16

How does the rabies virus cause nervous cell damage?

Answer 16

does not hide from immune system, replication causes rabies glycoproteins to be displaced on cell surface -> B cells come and kill

Question 17

Describe rabies pathogenesis - how it is contracted and symptoms it causes

Answer 17

rabid raccoon/dog bites a human transferring rabis virus from the saliva to the muscle, replicates and gets to a peripheral nerve which it uses to travel to the CNS (takes time). Causes aggression and thirst but also muscle spasm and terror on attempt to drink water (virus doesn’t want to be diluted out of saliva)

Question 18

Alpha herpesviruses (HSV1, 2, VZV) have night neuro what but low neuro what?

Answer 18

high neurovirulence
low neuroinvasiveness
-> causes disease in the nervous system but less likely in the CNS

Question 19

Describe how HSV can cause encephalitis

Answer 19

RARE. if virus enter the blood it can replicate in the liver and spleen then get into the brain and spinal cord to cause severe encephalitis

Question 20

Which virus does not have to grow in nerve cells?

Answer 20

poliovirus

Question 21

What is the pathogenesis of poliovirus?

Answer 21

enterovirus (ingested) replicates in regional lymph nodes then gets into the blood (free virus) enters the spinal cord and replicates in motor neuron cells - cytocidal virus -> paralysis (commonly of lower limbs)

Question 22

Which viruses commonly cause meningitis in summer/autumn months?

Answer 22

Enteroviruses