Viral CNS infxn Flashcards
Viral Meningitis
Usually mild and self-resolving
Bacterial Meningitis
Life threatening
Predictors of bacterial etiology regarding meningitis?
- Low CSF glucose
- High CSF protein
- High CSF white count
- High CSF neutrophil count
The presence of any one of these predicts bacterial etiology with 99% certainty
Viral meningitis appearance
- Pts don’t appear extremely ill, are NOT ENCEPHALOPATHIC
- fever and malaise
- headache
- neck stiffness
- low back pain
Usually lasts 10-14 days
Recurrent viral meningitis can result from persistent or latent infections (HSV)
Most common cause of Viral Meningitis?
Enteroviruses….80%
What are some of the enteroviruses that cause viral meningitis?
echo, coxsackie, enterovirus 71
10% of viral meningitis caused by
Mumps
How are enteroviruses spread
oral/fecal route
HSV-2 generally causes
genital herpes
Can also be a cause of RECURRENT aseptic meningitis
Mollerat cells in the CSF?
HSV-2
HIV and VZV cause?
recurrent meningitis
30% of viral encephalitis caused by
Arboviruses (arthropod born viruses) such as St. Louis, West Nile, La Crosse
Transmitted by mosquitos and ticks
Predominantly affects the children or the elderly
25% of viral encephalitis caused by
Enteroviruses (echo, coxsackie, entero 71)
25% of viral encephalitis caused by
Herpes Simplex 1
What is important to recognize about HSV-1
It is a deadly cause of encephalitis if not treated promptly with acyclovir
Clinical course of viral encephalitis
fever headache lethargy URI Confusion then.... seizures, coma, death in some cases
If you see Fever, headache, lethargy and a prodromal URTI…think encephalitis
- Looks exactly like bacterial meningitis so you MUST treat it empirically before you really even know what the diagnosis is
What is the prognosis associated with mosquito born viruses?
poor
What is the characteristic site of damage in HSV encephalitis?
Temporal lobe….MRI shows necrosis in temporal lobe
Diagnosis of HSV1?
PCR is definitive but false negatives occur
Mortality without tx for HSV1
70%
Flaviviruses
St. Louis and West Nile
Flavivirus morphology
Small, enveloped, +RNA viruses
Flavivirus replication cycle
1) Enters by receptor mediated endocytosis
2) + strand genome is translated into single polyprotein, that polyprotein is cleaved.
3) virions bud into intracellular organelles and are transported via the eocytotic pathway and released
All members of the flavivirus genus are transmitted how>
through insect vectors….They are the most important group of arboviruses
Flaviviruses that cause disease in the US
- St. Louis, West Nile, Dengue fever, Yellow Fever
SWDY
Disease course of flavivirus
Virus replicates at the site of inoculation.
Initial infection = primary viremia (mild fever, chills, aches)
Usually cleared by reticuloendothelial system (spleen, liver, etc..)
Continued replication can give rise to a secondary viremia which can invade CNS. Generally would only occur in children, elderly, or immunocompromised
SLE ( St. Louis Encephalitis) syndromes and symptoms slide
SLE found in north, central, and south america
- Onset characterized by flu-like symtpms, most do not progress. If secondary viremia occurs, it can lead to acute or subacute neurological signs and symptoms associated with CNS disease.