Viral meningitis and encephalitis Flashcards
What is meningitis?
Inflammation of meninges
What is encephalitis?
Inflammation of brain tissue
What is meningoencephalitis?
I nflammation of meninges and brain tissue
What is aseptic meningitis?
Clinical picture of meningitis observed (i.e. increased lymphocytes, increased protein, normal/reduced glucose)
BUT negative bacterial culture
What is the main cause of aseptic meningitis?
Viruses mainly but also..
- listeria
- TB
- Syphilis (can not be grown in culture)
What group of people is viral meningitis most common in?
Children/neonates
What are the main viruses that cause viral meningitis?
1/3 cases = unknown Enteroviruses e,g echovirus, coxsackie - herpes viruses - HSV, EBV, VZV, cytomegalovirus - Mumps virus - HIV
- Measles
- Influenza/parainfluenza
Which herpes simplex virus is more associated with meningitis?
HSV II
What is the pathogenies of viral meningitis (i.e. how does it occur?)
Colonisation of mucosal surfaces
invasion of epithelial cells
Replication in cells
Dissemination and invasion in CNS - blood/nerves
What are the clinical features of viral meningitis?
- Very similar to bacterial!
- Fever
- -/+ rash (unusual)
- ‘Meningism’ i.e. headache, neck stiffness, photophobia
- Sometimes viral prodrome i.e. evidence of previous viral infection
What to look out for in infant viral meningitis?
Meningeal signs might be absent
- Nuchal rigidity (neck stiffness)
- Bulging anterior fontanelle (increasing intracranial pressure)
what is the Kernigs sign?
With hips and knee flexed at 90 degrees, cannot extend knee due to pain/stiffness in hamstrings
What is the Brudzinski’s sign?
Flexing the neck (pain) will cause the hips and knees to flex
What is nuchal rigidity?
Resistance to flexion of neck
What investigations should you perform?
Blood - FBC, U&E, CRP, clotting
CT scan (maybe)
Lumbar puncture
- Microscopy
- Glucose (CSF:Plasma)
- Protein
- PCRWhat is pleocytosis?
White blood cells in CSF
What are the CSF features with viral meningitis?
- Lymphocytes in CSF approx 500 (polymorphs i..e neutrophils maybe in first 24hrs)
- Normal/reduced glucose (CSF:Plasma ratio; usually 50-66%)
- Increased protein (0.5-1.0; normal - 0.2-0.4)
What is the treatment for viral meningitis?
Start appropriate IV antibiotics (risk of bacterial meningitis e.g. cefotoxime)
No evidence for use of antivirals (e.g. aciclovir) for viral meningitis - supportive therapy
Which HSV, HSVI or II, is more commonly associated with meningitis?
HSVII (genital warts and meningitis) - meningitis can follow genital lesions
HSVI (cold sores and viral ENCEPHALITIS)
What are the main cause of viral encephalitis?
Herpes simplex virus I and II (90% are HSV I)
VZV, CMV, EBV Measles Mumps Enterovirus (inc polio) HIV
Other causes - acute disseminated encephalomyopathy (ADEM)
What are the clinical features of viral encephalitis?
Altered mental state (bizarre/abnormal behaviour) (Not in meningitis)
Fever
Headache
Meningism (may be absent)
+/- focal neurological symptoms
e.g. seizures**, weakness, dysphagia/asphasgia, CN palsy, ataxia
What investigations should be performed for viral encephalitis?
- Blood tests
- CT BEFORE LP
- MRI - see changes typical of HSV
- Lumbar puncture - microscopy, protein, glucose, viral PCR
What is the treatment for viral encephalitis?
Focused on HSV encephalitis
Aciclovir
What is acute disseminated encephalomyelopathy? (ADEM)
Immune mediated CNS demyelination following viral illness or vaccination
CSF findings are same as viral meningitis
