CNS Infections - Viral Flashcards
HSV-1 -What infections?
Where does it act/attack?
What drug for treatment?
- Keratoconjunctivitis (dedritic ulcers), Encephalitis (temporal lobe)
- Trigeminal ganglia
- Acyclovir!
- Eye-Trifluridine
HSV-2 (herpes genitalis) - What infections?
Where does it act/attack?
What drug for treatment?
- Aseptic meningitis, myelitis, neonatal herpes-meningitis, cerivial carcinogenesis
- Sacral ganglia
- Acyclovir!
VZV (chicken pox, zoster-shingles) - What infections?
Where does it act/attack?
What drug for treatment?
- Meningoencephalitis, Keratitis
- Trigeminal and dorsal root ganglia
- Acyclovir, Varicella Vaccine
EBV (infectious mononucleosis) -What infections?
Where does it act/attack?
What drug for treatment?
- Meningeoencephalitis
- B lymphocytes
- Self limited
CMV (cytomegalovirus) - What infections?
Where does it act/attack?
What drug for treatment?
- Encephalitis, Chorioretinitis, Alzheimer’s Disease!
- Mononuclear cells
- Ganciclovir
What are the main causes of encephalitis?
- Alphaherpesviruses (HSV & VZV)
- Postinfectious immune responses (Measles, mumps, ruebella, VZV, influenza)
- Tuberculosis
- Autoimmune disorders
- Enteroviruses (poliovirus, coxackie A and B, Echoviru, Enterovirus 71, Parechovirus –> all except 71 cause fever and all are spread via fecal-to-oral route)
- Other minor/rare causes
a. Arborviruses (WNV, Powassan virus, La Crosse Virus, etc.)
b. Other herpesviruses (immunocompromised)
c. JC virus (immunocompromised)
d. Respiratory viruses
e. Rabies
What viruses are common in the summer?
Enteroviruses
What are the polyomaviruses?
JC and BK viruses
Describe JC and BK viruses?
Small viruses with circular dsDNA genomes of around 5,000 bases.
They do early & late gene expression:
-Early: T (transformation) proteins. Large and small.
-Large T = cell growth promotion and transformation
-Small T = viral DNA replication
-Late = capsid (3) proteins
How are polymaviruses spread and how do they infect others?
- Virus is probably acquired through the resp. or oral route
- Infects tonsils & lymphocytes
- Spreads by viremia to the kidneys in early life
- Virus is ubiquitous and infections are typically asymptomatic (almost everyone has this)
- Establishes persistent and latent infection in organs like kidneys and lungs
What happens with JC virus in immunocompromised people?
JC virus is reactivated and can spread to the brain. Here JC virus causes PML, a “slow virus” disease [ex: similar to subacute sclerosing pan encephalitis (SSPE) of measles]
What happens when someone is immunosuppressed and infected with JC virus?
Reactivated virus can:
- BK virus multiplies in urinary tract and causes viruria and possible hemorrhagic cystitis
- JC virus viremia goes to the CNS and causes possible PML
What happens in PML (progressive multifocal leukoencephalopathy)?
JC virus partially transforms astrocytes and kills oligodendrocytes. This causes lesion characteristic of JC viral infection as well as sites of demyelination.
–Demyelinated PML lesions (only in white matter) also contain unusual large astrocytes and oligodendroglial cells with very large nuclei –> look kind of like cancer
How can you diagnose JC Virus in the lab?
- In situ immunofluorescence, DNA probe analysis, and PCR analysis of CSF, urine or biopsy material
- –Urine cytologic tests can reveal the presence of JC or BK virus infection by revealing the existence of enlarged cell with dense, basophilic intranuclear inclusions resembling those induced by CMV
- -Usually NOT cultured - too difficult to isolate
What is used to treat JC virus?
Cidofovir (used to treat polyomavirus infections)
How do you define encephalitis?
- Evidence of encephalopathy (altered level of consciousness persisting for more than 24 hours)
- AND at least two of the following:
a. Fever or history of fever
b. Seizures/focal neurological deficits
c. CSF pleocytosis
d. Electroencephalogram characteristics consistant with encephalitis
e. Neuroimaging abnormalities consistent with encephalitis
What is the timing and incidence of viral encephalitis?
Can happen year-round in any age group. Overall incidence of viral encephalitis is higher in children.
What should you think about in diagnosis viral encephalitis?
- Vaccination history (MMR)
- Immune system function (EBV, HCMV, HHV-6, JC virus)
- Time of year
- Later summer/early fall (Enteroviruses)
- Mosquito or tick bites (WNV & other arboviruses, RMSF)
- Winter (adenoviruses, influnza virus) - Postinfectious (Measles, Mumps, Rubella, VZV, and Influenza)
- Animal bite (Rabies)
What are common physical exam findings with viral encephalitis?
- Low grade fever (under 102F)
- Pulse rate, respiratory rate, and blood pressure typically normal
- Signs of confusion/focal neurological deficitis
- –Weakness on one side of the body
What are laboratory findings with viral encephalitis?
ALL LABS NORMAL!!
- Hematocrit should be normal
- WBC should be normal (if taken from blood stream)
- –Differential (cells) should be normal
- Blood gases should be normal
- Serum chemistries should be normal
What does a head MRI show for viral encephalitis?
- Can show irregular areas of hemorrhagic necrosis
- –Temporal lobe for HSV, etc.
What does lumbar puncture/CSF show for viral encephalitis?
-Can show CSF pleocytosis (WBCs > 5 ul - primarily lymphocytes), RBCs present/high, normal glucose concentration, elevated protein concentration
How can you do a definitive diagnosis of viral encephalitis?
- Isolate virus from the CSF or brain (grow virus in tissue culture cells)
- Serology of antibodies against virus
- PCR detection of viral genome
What’s the diagnosis?
- Change in behavior
- Fever & headache (2 days)
- left-sided weakness
- temporal lobe (irregular area of hemorrhagic necrosis)
HSV - viral encephalitis
