Micro: Viral CNS Infections Flashcards Preview

MS2 Unit 3 > Micro: Viral CNS Infections > Flashcards

Flashcards in Micro: Viral CNS Infections Deck (36):
1

What are the ways in which viruses can access the CNS?

1. Olfactory route
2. Neuronal
3. Hematogenous

2

Meningitis definition

Inflammation of the lining of the brain. Aseptic meningitis is NOT caused by bacteria

3

Encephalitis defitinition

Inflammation of the brain tissues

4

Meningoencephalitis definition

Widespread infection of the meninges and brain

5

Cause of aseptic meningitis

Viruses, fungi, TB, infections near the CNS
- 80% enteroviruses, 10% HSV 1 and 2, 10% arboviruses

6

Symptoms of aseptic meningitis

Mental status is normal, this can distinguish from encephalitis
- Headache, fever, chills, stiff neck, malaise, sore throut, N/V, abd pain, rash, myalgias, photophobia

7

Diagnosis of aseptic meningitis

Elevated WBC count in spinal fluid, no bacteria
Virus may be detected in CSF

8

Treatment of aseptic meningitis

Supportive care
Drugs exist for herpesvirus, fungal, and mycobacteria infections

9

Prognosis of aseptic meningitis

Usually benign, resolves in 2 weeks.
Rare complication: encephalitis

10

Brudzinski's sign

Indicative of meningitis
- Neck is so stiff that the knees flex when the neck is flexed

11

Encephalitis incidence

Rare, ~20,000 cases/year, mainly infants/elderly

12

Causes of encephalitis

Exposure to virus --> influx in immune cells in brain --> cerebral edema destroys neurons --> intracerebral hemorrhage (distinguishing feature from meningitis)

13

Symptoms of encephalitis

Altered mental status, fever, headache, vomiting, photophobia, stiff neck, confusion, sleepiness, irritability, stumbling
Urgent: unresponsiveness, coma, seizures, muscle weakness, paralysis, memory loss, flat affect, withdrawal, poor judgment

14

Diagnosis of encephalitis

Spinal tap indicates inflammation in CSF, may be blood or virus. PCR is gold standard.
- EEG for seizures
- Brain MRI or CT may show foci of inflammation or hemorrhage

15

Treatment of encephalitis

Supportive care and symptom relief
Antivirals for herpes, antiseizures, anti-inflammatories, sedatives

16

Prognosis of encephalitis

Ranges from benign with full recovery to severe, fatal

17

Pathogenesis of viral CNS disease

1. Death of neurons -- cytolytic viruses can directly kill tissues
2. Host factors: age - infants/elderly. Immune status, genetics, activity
3. Acute disseminated encephalomyselitis (ADEM) - postinfectious encephalitis follows viral infection by 1-2 weeks. Associated w/ measles, mumps, VZV, influenza, parainfluenza viruses. Autoimmune.

18

Herpesviruses

HSV2 >> HSV1
- also VZV, CMV, EMV in immunocompromised
- in weak host, CNS infections progress to severe encephalitis
- treat HSV and VZV aggressively with acyclovir

19

HSV1 encephalitis prevalence

The most common cause of sporadic viral encephalitis (10-20% of all cases)

20

HSV1 encephalitis routes of infection

Primary HSV1 in oropharynx --> trigem --> CNS

Recurrent HSV1 --> trigem --> CNS

Reactivation "in situ" HSV1 --> CNS

21

HSV1 encephalitis symptoms

altered mental status, focal cranial nerve deficits, hemiparesis, slurred speech, stumbling, seizures, fever

22

HSV1 encephalitis Dx

Gold standard: PCR of CSF for HSV and other viruses
MRI shows predominantly unilateral temporal lobe abnormalities

23

Pathogenesis of rabies

- Transmitted by saliva via bite from rabid animal or by aerosols in caves populated by infected bats
- Replicates in muscle at bite site
- Incubation weeks-months
- Infects peripheral nerves, travels to brain
- Replication in brain causes hydrophobia, seizures, hallucinations, paralysis, coma, death
- Spreads to salivary glands from where it is transmitted
- Postexposure immunization can prevent disease due to long incubation period

24

Picornaviruses transmission

enteroviruses are fecal-oral

25

Picornavirus risk factors

Poliovirus --> young kids asymptomatic/mild disease, older kids + adults asymptomatic to paralytic.
Coxsackievirus and enterovirus--> neonates

26

Distribution of picornaviruses

- Ubiquitous, poliovirus nearly eradicated
- Enteroviruses more common in SUMMER

27

Vaccines or antivirals for picornaviruses

Poliovirus: live oral or inactivated polio vaccine
- No vaccines/antivirals for other enteroviruses, rhinoviruses

28

Picornavirus dissemination

Replication in oropharynx and intestine --> lymph node --> blood --> skin, muscle, brain, meninges

29

Togavirus examples

VEE, EEE, WEE, Chikungunya, Rubella

30

Togavirus dissemination

Skin --> blood --> macrophages + spleen, lymphnodes --> brain

31

Flaviviruses that cause encephalitis

Japanese encephalitis, West Nile, St. Louis encephalitis, Russian spring-summer encephalitis, Powassan virus

32

Flavivirus dissemination

Mucosal surface --> lymph node --> primary viremia in blood --> vascular endothelium, macrophage, liver, spleen, lymph node --> secondary viremia causing encephalitis, yellow fever hepatitis, hemorrhagic fever

33

Flavivirus transmission

Mosquitos, ticks

34

Flavivirus distribution

Determined by habitat of vector: Aedes mosquito is urban, Culex is forest and urban
More common in SUMMER

35

Flavivirus vaccines/antivirals

- Live attenuated vaccine for yellow fever and Japanese encephalitis
- No antivirals

36

West Nile meningoencephalitis

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