L11 – Infections of the Nervous System: Viral Infections Flashcards
3 pathogenesis pathways for viral CNS diseases?
1) Delayed/ acoompanying inflammatory reactions
2) Direct cytolytic infection and neruonal damage
3) Post-infectious syndromes and demyelination
Explain how viral CNS infection can cause demyelination.
virus replicates outside CNS»_space; cross-reacting immune response to myelin / dysregulation of immune response»_space; demyelination of CNS
Typical temporal features of viral CNS infection?
Biphasic illness
CNS symptoms follow 2-12 days after initial illness
Presentation may be acute, subacute, or chronic
Relate the terms given to infection of different parts of the CNS.
- Brain = encephalitis;
- Meninges = meningitis
- Spinal cord = myelitis;
- Peripheral nerves = neuritis / neuropathy
Many viral infections may involve more than one site e.g. meningo-encephalitis.
List 5 clinical symptoms and signs of viral CNS infection.
1) Meningeal irritation: Neck stiffness, Kernig’s and Brudzinski’s sign
2) Encephalopathic signs: Alternation of consciousness, fits and seizures
3) Increased ICP: headache, vomiting
4) Focal neurological signs: paralysis, aphonic
5) Systemic signs: fever, lethargy
Compare between pyogenic, viral and TB/ Fungal meningitis: appearance of CSF?
Pyogenic: Turbid
Viral: Clear/ sl. turbid
TB/ Fungal: Clear/ sl. turbid
Compare between pyogenic, viral and TB/ Fungal meningitis: Total cells and predominant WBC.
Pyogenic: >500, PMN
Viral: <500, lymphocytic
TB/ Fungal: <500, lymphocytic
Compare between pyogenic, viral and TB/ Fungal meningitis: Protein and glucose
Pyogenic: Very low glucose, Very high protein
Viral: Normal glucose, high protein
TB/ Fungal: low glucose, very high protein
Compare between pyogenic, viral and TB/ Fungal meningitis: Gram stain and acid-fast stain
Pyogenic: 65 to 95%
Viral: -ve
TB/ Fungal: -ve, TB acid-fast stain only
Viral isolation from CSF is good or poor for which type of CNS infections?
Good isolation: Viral meningitis
Poor isolation: viral encephalitis, Post-infectious encephalitis (doesnt penetrate BBB)
Isolation rate best, early in illness
PCR of CSF is used for Dx of which viral CNS infections.
–herpes simplex encephalitis.
–CMV encephalitis / myelitis.
–VZV encephalitis /meningitis/ myelitis.
–more sensitive than culture in diagnosis of enterovirus.
List all diagnostic tests used for viral CNS infections?
Throat swab (mumps, enteroviruses)
Stool sample (enterovirus)
PCR of CSF (HSV, CMV, VZV, enterovirus)
CSF serology
Brain biopsy
Blood serology
List all serological tests for dx of viral CNS infections?
- Rising Ab titre (paired sera): Flu A/B, VZV, HSV, entero, mycoplasma, (mumps, measles)
- IgM Ab (single sera): JEV, EBV, (CMV)
- Intra-thecal (in CSF) antibody synthesis (late presentation)
Why is serology for enterovirus not indicated in viral CNS infections?
problem of many serotypes and no common antigen
List common and less common viruses that cause viral meningitis
1) Common:
– Enteroviruses (ECHO, Coxsackie A/B).(summer months)
– H.simplex type 2 (genital herpes)
2) Less common:
– Mumps (immunisation has made less common)
– Lymphocytic choriomeningitis (LCM) (assn. with rodents)
– HIV seroconversion illness
Properties of enteroviruses: family, genetic material? Is their protective immunity the same?
Family Picornaviruses.
RNA viruses
Single +ve stranded,
non-enveloped
share a few common antigens, but protective immunity is type specific
List 7 clinically significant enteroviruses?
Polio Cox A Cox B ECHO EV 68, 70, 71
Hand foot and mouth disease is caused by which viruses?
Enterovirus: Cox A (A16), EV71
Which enteroviruses can cause asymptomatic infection?
All types
List some general symptoms caused by most enterovirus infections?
- Asymptomatic
- Fever, rash
- Flaccid paralysis **
- Meningitis
- Carditis
Conjunctivitis is caused by which enterovirus subtypes?
- Cox A (A24)
- EV70
Herpangina is caused by which enterovirus subtype? *small, blister-like ulcers on the roof of the mouth and in the back of the throat. *
Cox A