CNS Infections - Viral Meningitis and Encephalitis (26) Flashcards
Meningitis
Inflammation of meninges
Encephalitis
Inflammation of the brain
Meningo-encephalitis
Inflammation of brain and meninges
Aseptic meningitis WBC
Above 5X10^6/L in CSF (negative bacterial culture)
Common causes of aseptic meningitis
Viruses, partially treated bacterial meningitis, Listeria, TB, syphilis, malignancy, autoimmune conditions, drugs
Virion
Basic infectious particle of virus
Virus structure
Nucleic acid (DNA/RNA), capsid, lipid envelope (derived from host cell membrane), some contain other proteins/enzymes
What is a capsid?
Protein coat, made up of capsomeres (subunits)
Epidemiology of viral meningitis
Common neonates and under 5,
5-15 cases per 100,000
Aetiology of viral meningitis
- Enteroviruses (echoviruses, coxsackie, parch, enteroviruses 70 and 71, polio)
- Herpes virus (HSV 2), VZV, CMV, EBV, HHV6, HHV7
- Arboviruses
- Mumps
- HIV
- Adenovirus
- Measles
- Influenza
- Parainfluenza type 3
- Lymphocytic choriomeningitis virus (LCMV)
What’s the lead cause of viral meningitis?
Enteroviruses
What are common causes of viral meningitis?
Enterovirus, HSV 2, VZV, Mumps, HIV
What percentage of viral meningitis cause unknown?
35%
Pathogenesis of viral meningitis
Colonisation of mucosal surfaces, invasion of epithelial surface, replication in cells, dissemination and CNS invasion
How does viral meningitis dissemination into CNS?
Via cerebral microvascular endothelial cells, via choroid plexus epithelium, spread along olfactory nerve
What are symptoms in VM mainly due to?
Inflammatory response in CNS
Clinical presentation of viral meningitis
Fever, Meningism (headache, neck stiffness, photophobia), lethargy, myalgia, arthralgia, sore throat, rash, diarrhoea and vomiting
Children clinical presentation of viral meningitis
Neonates/infants meningeal signs absent, nuchal rigidity/neck stiffness and bulging anterior fontanelle
Kernig’s sign
Hip and knee flexed to 90 degrees, knee cannot be extended due to pain/stiffness in hamstrings
Brudzinski’s sign
Flexing the neck causes hip and knees to flex