Viral Encephalitis- Aucoin Flashcards
What are the viral infections of the CNS?
- aseptic meningitis
- viral encephalitis
- paralysis
- AIDS dementia
- rabies
- prions
CNS infections occur within the (blank) or (blank), they may be associated with significant morbidity and mortality.
Who is this especially dangerous in?
cranium or spinal cord.
infants and immunocompromised patients
Most patients with CNS infections present with the clinical features of …?
fever, headache, altered mental status, or focal neurologic deficits (speech, sight issues, paralysis)
The clinical presentation of a CNS infection may be (blank, blank or blank) depending on the virulence of the infecting agent and the (blank) of the infection.
acute, subacute, or chronic
location
Numerous (blank) etiologies may account for syndromes that mimic CNS infections
noninfectious
Viruses colonize mucosal surfaces and then the host posseses numerous barriers to prevent (blank)
viral entry
If one has previous contact with a virus, the mucosa of the GI and respiratory tracts may be coated with (blank)
secretory IgA
What does IgA do?
neutralizes the virus and prevents attachment and subsequent cell penetration
what do viruses have to do to get to the CNS?
escape host defense mechanisms, replicate and disseminate
The steps of infection of most neurotropic viruses is….
1) non neuronal sites (initially at portal of entry)
2) establish viremia
3) cross BBB to invade the CNS
What is the most common route that viruses get into the body? What do viruses have to overcome in the mucosal surfaces to become dangerous?
respiratory> GI
-mucus, cilia, IgA
In the GI tract, what kind of viruses can survive in there?
naked capsid viruses
(blank) initially multiply in the peritonsillar lymphatics, peyers patches, lamina propria of the intestine, and vascular endotheial cells
Enteroviruses
(blank) may mediate virus penetration from the gut lumen to lymphoid cells
M cells
After viremia, viral particles are normally cleared by (blank)
phagocytic cells
SOme viruses are sneaky and can avoid been cleared by host cells by doing what?
associating with certain cells such as growing and being transported with phagocytic cells
What types of viruses grow and are transported in phagocytic cells?
measles, mumps, herpes
What are the different mechanisms in which CNS invasion by viruses occurs?
- direct invasion across cerebral capillary endothelial cells
- infection of glia
- transport via infected immune cells (monocytes) b/w cerebral capillary and endothelial cells
- olfactory or peripheral nerves
What do glial cells do?
- surround neurons and hold them in place
- supply nutrients and oxygen to neurons
- insulate one neuron from another
- destroy pathogens and remove dead neurons
Some viruses such as HIV, use a “trojan horse” method of entry into the BBB. explain this.
they enter monocytes and during normal turnover of perivascular macrophages or as a result of the production of pro-inflammatory mediators compromising the barrier, monocytes with the infecting virus will pass through the BBB
SOme viruses, like HTLV bind to (blank) such as glucose transport type 1 (GLUT 1), allowing for the infection of endothelial cells and release of pro-inflammatory mediators which will make the BBB leaky.
endothelial receptors
Viral CNS entry also occurs through (blank). HSV1 travels like this. What facilitates this?
peripheral neurons nectin 1 (expressed axons)
How does HSV1 replicate and infect?
it utilizes retrograde transport up the axon into the dendrite and then replicates in the nucleus. It will then utilize anterograde transport to cause a flare up
Rabies virus and HSV-1 are released at a synapse and use a (blank) pathway to infect neighboring neurons.
retrograde trans-synaptic
Measles virus dissemination between neurons is thought to occur through (blank) between neighboring cells.
microfusions
dendrite and axon kiss for a second and pass virus
In the case of HSV-1, anterograde transport (from cell body to axon) can lead to infection of neighboring cells when the virus exits via (blank) before reaching the axon termini. During HSV-1 reactivation, the virus uses the anterograde system (dashed black arrow) to reach axon termini and reinfect epithelial cells by binding to (blank) or herpesvirus entry mediator (HVEM) receptors.
axonal varicosities
nectin 1
(blank) are contractile cells that wrap around the endothelial cells of capillaries and venules throughout the body.
What do they do?
Pericytes
-regulate capillary blood flow, clearance and phagocytosis of cellular debris and permeability of BBB
Viruses in the CNS (in order to spread) must induce (blank) changes
cellular
Viral entry into the (blank) space leads to dispersion of virus within the CSF in contact with meningeal cells. If this happens where can the infection spread?
subarachnoid
-glia and neurons
Once viral infection of the CNS occurs, (blank) cells usually accumulate
inflammatory
The initial inflammatory response appears immunologically specific and consists of a population of (Blank) sensitized by the virus
lymphocytes
(blank) may respond to a virus-specific protein that diffuses or is transported to the luminal surface of the endothelium
monocytes
When viruses pass through endothelial cells, this will release (blank)
cytokines-> IFNy and IL-6
After development of a CSF inflammatory response, alterations in the (Blank) will permit the traversal into CSF of (blank) including (blank)
BBB
serum proteins
Ig
Intracerebral accumulation of Ig is reflected by what?
increase in CSF-to-serum ratio of specific Ig that persists for several weeks after infection
Which immune response is more important to get rid of viruses?
T-cell responses
What may develop in patients with depressed cell-mediated immunity?
Chronic viral infections
Failure of an immune response to develop results in the virus escaping (blank)
immune surveillance
If you see a hemorrhage in the temporal lobe, then what is the virus that caused it?
herpes simplex virus
(Blank) is the inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges
meningitis
How is meningitis identified?
pleocytosis -> abnormal number of WBC in CSF
The common etiologic agents of acute meningitis are (blank). But bacteria can too, what are some causes of bacterial meningitis?
viruses
-strep pneumoniae, N meningitis, listeria monocytogenes
Acute meningitis is clinically defined as a syndrome characterized by the onset of meningeal symptoms over the course of (blank)
hours to up to several days
T or F
pygoenic bacteria are NOT the cause of aseptic meningitis
T
What is aseptic meningitis (viral)?
when the cause of meningitis is not apparent after initial eval and routine stains and cultures of CSF
Most aseptic viral meningitis are caused by (blank) and are (more/less) severe than bacterial meningitis
enterovirus
less
How do you treat aseptic viral meningitis? What tis the season for aseptic viral meningitis?
-no specific-> symptoms just usually resolve.
Summer
A (small/large) percentage of people with enterovirus infections develop meningitis
small
What are the 3 most common causes of aseptic meningitis?
- nonpolio enteroviruses (coxsackie, echovirus)
- mumps virus
- herpesvirus
What are some less common causes of aseptic meningitis?
- arboviruses
- lymphocytic choriomeningitis virus (LCMV)
- HIV
- adenovirus
- influenza virus
- measles virus
Viral meningitis occurs mostly in…?
children under 5 (can happen from changing a diaper or using a toilet and not properly washing hands afterwards)
Meningitis infection is characterized by what 3 major symptoms?
sudden onset of fever
headache
stiff neck
What are other symptoms of viral meningitis?
- nausea
- vomiting
- photophobia (sensitivity to light)
- altered mental status
The symptoms of viral meningitis usually last how many days?
7-10 days
people with normal immune systems usually recover completely
If meningitis is suspected, what do you get?
blood or CSF fluid samples
(blank) are the leading recognizable cause of aeptic meningitis, accounting for 85% to 95% of all cases in which a pathogen is identified.
Enteroviruses
Why does warm weather facilitate the spread of enterovirus?
-wearing sparse clothing may facilitate the fecal-oral spread of these viruses
Enteroviruses have been recovered from (blank); and disease has been reported after swimming in (blank) water
wastewater and sewage
sewage-contaminated seawater
In the US, the (blank) most commonly occuring enteroviral serotypes account for most all of the isolates
14
What were the predominant enteroviruses associated with viral meningitis?
- echoviruses 30,11,9,6 and 7
- coxsackieviruses B2 and A9
- echoviruses 18 and 16
- coxsackieviruses B1 and B3
- enterovirus 71
- coxsackievirus B4
- echovirus 25
What kind of virus is the coxsackie virus?
Who typically gets it?
How does it typically get transmitted?
picornaviridae-> enterovirus
- young people (naive immune system)
- fecal-oral and respiratory aerosals
What is this:
herpangina (ulcers in the oropharynx, fever, sore throat)
-AKA hand foot mouth disease due ulcer formation
Group A coxsackie virus
What is this:
- pleuodynia (fever and severe pleuritic-type chest pain)
- myocarditis (fever, chest pain, and signs of CHF)
Group B coxsackie virus
Both Coxsackie A and B can cause what?
How do you diagnose it?
How do you treat it?
aesptic meningitis and mild paralysis
- PCR of enteroviral RNA in spinal fluid
- no treatment
What kind of virus is an echovirus?
- how many serotypes?
- How is it transmitted?
picornaviridae-> enterovirus
30 serotypes
fecal-oral route and pool water
What does echovirus cause?
How do you diagnose and treat?
- leading cause (along with coxsackie virus) of aseptic (viral) meningitis
- upper respiratory infection, febrile illness, infantile diarrhea, and hemorrhagic conjunctivitis
- hand foot and mouth disease
-PCR, you dont treat it (no vaccine, no therapy)
Stiff neck, photophobia, and a campground pool should trigger you to think about what viruses?
Coxsackievirus and Echovirus
In an unimmunized population, (blank) is one of the most common causes of aseptic meningitis and encephalitis
mumps
Meningitis is estimated to occur in (Blank) percent of mumps patients
10-30%
CNS disease caused by mumps virus can occur in patients without evidence of (blank)
parotitis
(blank) is the most common neurologic manifestation of ithe mumps virus and is usually benign and is a self-limited process.
Meningitis
What age and gender is most often affected with mumps?
- males (2 to 5 times more likely than females)
- ages 5-9
What does the mumps virus cause?
When does it occur?
How is it transmitted?
How many serotypes does it have?
swelling of the parotid gland
- childhood
- respiratory droplets
- one
The mumps virus infects the upper respiratory tract and spreads via blood to…..?
How do you diagnose the mumps?
parotid glands, testes, ovaries, pancreas and some cases, meninges
-clinically (testing is available though)
Is the incidence of mumps high in the US?
How do you prevent mumps?
low
immunization with live, attenuated vaccine
What kind of virus is Lymphocytic choriomeningitis (LCM)?
How is transmitted?
What is a common reservoir for LCM?
What is the distrubtion and fatality of LCM?
- arenavirus
- aerosal inhalation, ingestion of contaminated food
- hamster or house mice
- worldwide distribution w/ low case fatality rate (<1%)
What are the infections of the arenaviridae like?
What are the symptoms?
Whats the treatment?
How do you test for it?
most are asymptomatic
-influenza like symptoms, fever, headache, myalgia, malaise
OR
-Aseptic meningitis, fever, headache, and stiff neck in minority of patients
-No treatment or vaccine
-sero testing for IgM or IgG
If you have lab evidence of neurologic dysfunction and inflammation of brain parenchyma, what do you have?
encephalitis
(blank) of cases of encephalitis have unknown etiology
half
Of cases of encephalitis with identified etiologies, (blank) accounted for almost 2/3rds
viruses
What is the defined criteria for encephalitis?
Altered consciouness for 24 hours or more and at least one of the following characteristics: -fever -seizures -focal neurologic findings -CSF pleocytosis or -EEG or neuroimaging findings
6 members of the herpesvirus family cause well-described neurologic disease…. what are they?
- HSV1
- HSV2
- VZV (varicella-zoster)
- EBV (ebstein-barr)
- Cytomegalovirus (CMV)
- Human Herpes virus 6 (HHV-6)
When (blank) infect the CNS, the clinical presentation is non-specific and often confounding.
herpesviruses
The clinical urgency of herpes encephalitis is often underscored by progressive (blank, blank or even blank) and prompt diagnosis and tx rely heavily on (blank)
neurologic deficits
seizures
death
neuroimaging
How can HSV1 cause encephalitis?
through retrograde transmision following HSV-1 reactivation
Where does HSV lie dormant?
in the ganglion of the trigeminal cranial nerve