Viral Encephalitis

Question 1

Define

1. Encephalitis
2. Myelitis
3. Meningitis

Answer 1

1. inflammation of parenchyma
2. inflammation of white matter
3. inflammation of meninges

Question 2

Steps required for Neuronal Virus Infection (4)

Answer 2

1. Enter the neuron at the axon, sensory terminal, or cell body, depending on the site of infection
2. Transport the virus particle or subviral particle to the neuronal cell body where virus replication occurs (usually via microtubules)
3. Replicate the virus genome
4. Assemble virus particles that egress from the infected neuron in a directional manner

Question 3

Modes of CNS entry for viruses

Answer 3

1. olfactory nerve
2. hematogenous via lungs
3. endometrium or interstitial space
4. intestinal tract –> blood
5. bug bite –> blood

Question 4

Herpes

1. Geography
2. Age affected
3. Season
4. What does it infect/cause?

Answer 4

1. all
2. all
3. all
4. Focal CNS

Question 5

Herpes

1. What diseases can HSV cause?
2. What is a unique method of entry to CNS?
3. How serious is it?
4. What brings viruses from peripheral sites to CNS?

Answer 5

1. encephalittis, keratitis, mucocuteanous disease
2. olfactory neurons
3. Can be severe/fatal is untreated
4. retrograde transport

Question 6

Herpes Simplex

1. What does it usually do in neurons?
2. What 2 things can it do rarely?

Answer 6

1. usually latent
2. can be transported to epithelia –> lesions
3. can be transported to CNS –> lethal encephalitis

Question 7

Herpes Simplex Encephalitis

1. What can be given?
2. How effective is it?
3. What does peripheral blood show during CNS infections?
4. What about CSF?

Answer 7

1. acyclovir
2. not very effective
3. may not show any signs of inflammation
4. often does, shows low glucose, high protein, neutrophils, RBCs, high proteins

Question 8

Enterovirus

1. Geography
2. Age affected
3. Season
4. What does it infect/cause?

Answer 8

1. All
2. Children
3. Summer
4. Paralysis

Question 9

Enterovirus

1. Pathogenesis (4)
2. How many develop paralysis?

Answer 9

1. virus ingested
2. virus infects gut lymphoid tissue
3. virus goes to regional lymph nodes –> blood –> through BBB –> spinal cord;
4. virus excreted in feces
5. <1%

Question 10

Arbovirus

1. Geography
2. Age affected
3. Season
4. What does it infect/cause?

Answer 10

1. Tropics
2. Elderly (also immunocompromised)
3. Summer
4. Meningitis

Question 11

West Nile Virus

1. Type
2. What % of infectiouns cause recognizable disease?
3. Symptoms
4. Reservoir
5. Vector

Answer 11

1. Arbovirus
2. <1%
3. fever, headache, stiff neck, disorientation, muscle weakness, paralysis (meningitis-like symptoms)
4. Birds
5. mosquitoes

Question 12

Measles

1. Geography
2. Age affected
3. Season
4. What does it infect/cause?
5. Why is it vaccinated?

Answer 12

1. All
2. Children
3. All
4. SSPE
5. Has serious/deadly sequelae

Question 13

Measles: Acute Postinfectious encephalitis

1. Characteristic features
2. Etiology

Answer 13

1. no detectable virus; appears a short time after rash, perivascular inflammatory changes and demyelination
2. postulated: autoimmune rxn against brain tissue

Question 14

Measles: Acute Progressive infectious encephalitis

1. Characteristic features
2. Etiology

Answer 14

1. presence of complete virus; cytolytic replication in brain tissue; inflammation
2. nonrestricted virus replication due to absence of normal cell-bound immunity (rare)

Question 15

Measles: Subacute Sclerosing Pan-Encephalitis

1. Characteristic features
2. Etiology

Answer 15

1. Develops many years after acute disease, presence of viral inclusion bodies in brain cells, inflammation, general destruction of brain tissue
2. progressive dissemination of a defective virus infection in the presence of a normal immune response; no production of infectious extracellular particles (rare)

Question 16

Rabies

1. Geography
2. Age affected
3. Season
4. What does it infect/cause?

Answer 16

1. All
2. All
3. All
4. Caused by animal bites

Question 17

Rabies

1. general shape
2. What is on the membrane?
3. How dangerous is it?
4. What are reservoirs?

Answer 17

1. bullet
2. G proteins (glycoproteins)
3. uniformly fatal
4. raccoon, skunk, bat

Question 18

Rabies Pathogenesis (8)

Answer 18

1. inocculated via bite
2. replicates in muscle
3. virion enters peripheral nervous system
4. passive ascent via sensory fibers
5. replication in dorsal ganglion
6. rapid ascent in spinal cord
7. infection of spinal cord, brainstem, cerebellum, and other brain structures
8. descending infection via nervous system to eye, salivary glands, skin, and other organs; virus found in tears/saliva

Question 19

Rabies

1. What prophylaxis is given? (2)
2. When is it symptomatic?
3. symptoms

Answer 19

1. wound site is cleanred;
2. passive immunity (Abs) given at wound site; can prevent infection if you stop it in the muscle
3. when virus is in CNS
4. fever, anorexia, N/V, hyperventilation, hypoxia, aphasia, pituitary dysfunction, hypoventilation, apnea, hypotension, cardiac arrythmia, cardiac arrest, coma, pneumothorax, intravascular thrombosis, secondary infections

Question 20

Prions

1. Geography
2. Age affected
3. Season
4. Etiology

Answer 20

1. All
2. All
3. All
4. Proteinaceous, non-viral etiology

Question 21

Infectious Prion Encephalopathies (4)

Answer 21

Kuru
Creutzfeld-Jakob Disease (using infected instruments in neurosurgery)
Gerstmann-Straussler-Scheinker (GSS disease)
Fatal familial insomnia

Question 22

Kuru Disease

1. How is it transmitted?
2. What is seen on histo?

Answer 22

1. canibalism of infected brain tissue

2. plaques in cerebellum, but not inflammation, no classical infectious material

Question 23

How do Prions differ from viruses?

Answer 23

1. lack nucleic acid & defined morphology;
2. can’t be disinfected by formaldehyde, proteases, heat, ionizing and UV radiation
3. has a long incubation period
4. lacks immune response, cytopathologic effect, interferon production, inflammatory response

Question 24

Prions

1. What do they do to neurons?
2. Symptoms

Answer 24

1. cause vacuolation of neurons (spongiform), amyloid-like plaques, gliosis
2. muscle control, shivering, tremors

Question 25

Prion Plaques: what happens?

Answer 25

1. prion may cause correctly changed protein to refold into altered state 2. altered proteins form aggregates 3. aggregates accumulate in neurons