CNS infections

Question 1

What are the most common viral infections?

Answer 1

Coxsackie and Echo Virus which are from the Enterovirus family

Question 2

What are the most common bacterial infections

Answer 2

H. Influenza, Streptococcus pneumoniae and neisseria meningitidis

Question 3

What are the normal CSF values

Answer 3

pressure = 150 mmH20, appearance = clear, WBC < 5 x 10^6, RBC = negative, Gram stain = negative, protein 60% of blood (>2.5mmol/L)

Question 4

What happens to these values upon infection

Answer 4

In viral 100s of lymphocytes /L and a slightly elevated protein count, In bacterial gram stain is positive, the pressure will be raised and appearance is cloudy, glusoce is also decrsased, there is alos 1000’s of neutrophils

Question 5

Typical clinical Symptoms in adults

Answer 5

• Fever
• Vomiting
• Nausea
• Headache
• Stiff neck
• Altered mental state
• Photophobia
• Seizures

Question 6

Pathophysiology of meningitis

Answer 6

Bacteria in nasoopharynx
1. Colonisation
2. Invasion into blood stream
3. Survival and multiplication
4. Crossing BBB
5. Invasion of meninges
6. Increased permeability of BBB
7. Increased ICP
8. Release of cytokines/inflammation
9. Neural damage
Therefore damage is mediated by immune response

Question 7

Most common form of neisseria meningitidis in Aus vs the Rest of the World

Answer 7

B and C in Aus while A in the rest of the world

Question 8

Typical infection profile

Answer 8

Children in developing countries

Question 9

How do you treat Meningitis

Answer 9

First - life support, then fluids then Antibiotics and then steriods

Question 10

What Antibiotics to treat meningitis

Answer 10

3rd generation cephlasporins (IV), penicillin and gentamicin

Question 11

What else is given if there is encephalitis

Answer 11

Aciclovir for the HSV that almost always causes encephalitis

Question 12

What is Neuroinvasive and Neurovirulence

Answer 12

Neuroinvasive: capable of infecting the central nervous sytem
Neurovirulent: capable of causing disease within the nervous system

Question 13

What is Reye’s Syndrome

Answer 13

Postinfective immmune disorder post influenza or Chickenpox in children, linked with aspirin use

Question 14

What other conditions are associated with infective encephalopathy

Answer 14

Chronic demyelinating disease, AIDS, Guillain-Barre Syndrome and POst-infective disorders

Question 15

List three ways that Virions can enter the CNS

Answer 15

Blood through the BBB
Retrograde transport through the PNS to the CNS
Through the olfactory bulb

Question 16

How does a virus cause inflammation?

Answer 16

Can kill neuron, leads to inflammation within brain. Now peripheral cells can cross the BBB and cause further inflammation. Leads to symptoms such as dementia, epilepsy, paralysis, deafness and blindness.

Question 17

Describe rabiesvirus

Answer 17

Is a -ve sense RNA virus with an envelope, mopves to the CNS via retrograde transport through PNS nerves and has high invassiveness and virulence in nerves

Question 18

Describe vaccination against rabies

Answer 18

Can be given post-infection as takes 12-0 days to reach the CNS, will bud from pre-synaptic junction to cross synapse and in doing so must bud. Can inject antibodies against the glycoproteins that are on the surface of PM in the budding process

Question 19

Why can’t Tcells attack neurons to remove virus

Answer 19

Don’t have MHC I

Question 20

How does Rabies propogate

Answer 20

Through Saliva

Question 21

Desribe the Pathogenesis of Herpes Virus

Answer 21

Will infect and can either move to lymph nodes and induce primary disease. 85% of virus will not induce diseasse and will be unapparent. the remain 15% can migrate to sensory ganglia in the face. Then they will migrate to the face and induce primary disease. Both pathways can lead to increased virus in the blood and promote invasion into the CNS through the BBB. Also virus can migrate up the PNS to the CNS. Once in the CNS can induce encephalopathy which has a very high mortality rate

Question 22

describe VZV

Answer 22

infection, lymph nodes, primary vireamia, liver + spleen for further replicatation, and then secondary vireamia. Can then migrate to skin to induce itch. SOme can then migrate to the dorsal route ganglia. If they become latent then they can induce shingles in dermatomes later in life

Question 23

Polio?

Answer 23

Will not always invade neurons, yet when it does it will be devestating. Will migrate to the anterior horn and kill motor neurons leading to paralysis. Is a +ve strand RNA virus with no envelope and is transmited through the FO route. Will replicate in the lymph nodes/tonsils and pass down the GIT tract before crossing the GIT and inducing vireamia. Then can infect motor neurons

Question 24

Enteroviruses?

Answer 24

Coxsackie A and B, Echovirus and EV71. Replicate in lymph nodes and can cause menigitis