Viral menigitis and encephalitis Flashcards
What is meningitis?
Inflammation of the meninges.
What is encephalitis?
Inflammation of the brain.
What is meningo-encephalitis?
Inflammation of the brain and meninges.
What is ‘aseptic’ meningitis?
Clinical picture of meningitis
White cell count >5x10^6/L (5/mm3) in cerebrospinal fluid (CSF)
Negative bacterial culture of the CSF
What are the possible causes of ‘aseptic’ meningitis?
- Partially treated bacterial meningitis
- Listeria
- TB
- Syphilis
- Malignancy
- Autoimmune conditions
- Drugs
What is the epidemiology of viral meningitis?
Common, especially in children/neonates
- Incidence 5-15 cases per 100,000
- around 3400 hospital cases in UK 2009-10
2 peaks of hospital admission:
- Neonates
- around age 5
What is the most common genera of viruses to cause viral meningitis?
Enteroviruses
- Echoviruses
- Coxsackie viruses
- Parecho viruses
- Enteroviruses 70 and 71
- Poliovirus
Which herpes viruses can cause meningitis?
Herpes Simplex Virus 2
- HSV 2»_space; HSV 1
Varicella Zoster Virus (VZV)
Cytomegalovirus (CMV)
Epstein Barr Virus (EBV)
HHV6, HHV7
In what percentage of viral meningitis cases is the aetiology unknown?
35%
What is the pathogenesis of infective meningitis?
Colonisation of mucosal surfaces
Invasion of epithelial surface
Replication in cells
Dissemination and CNS invasion
- Via cerebral microvascular endothelial cells
- Via choroid plexus epithelium
- Spread along the olfactory nerve
What causes the symptoms of meningitis?
Symptoms mainly due to inflammatory response in the CNS.
What is the clinical presentation of meningitis?
Fever
‘Meningism’
- Headache
- Neck stiffness
- Photophobia
Sometimes ‘viral’ prodrome (e.g. lethargy, myalgias, arthralgias, sore throat, D&V, rash)
What is the clinical presentation in neonates?
In neonates/infants meningeal signs may be absent
- Look for nuchal rigidity (neck stiffness) and bulging anterior fontanelle
What is Kernig’s sign?
With hip and knee flexed to 90 degrees, the knee cannot be extended due to pain/stiffness in the hamstrings
What is Brudzinski’s sign?
Flexing the neck causes the hips and knees to flex
What is nuchal rigidity?
Resistance to flexion of the neck
Under what circumstances should a CT be performed before an LP?
If raised intracranial pressure is suspected.
What are you looking for in the CSF?
Microscopy, Culture, Sensitivity (MC&S)
Protein
Glucose (must check blood glucose at same time)
Viral PCR: enteroviruses, HSV, VZV
What are the differences in CSF findings between viral and bacterial meningitis?
Opening pressure much higher in bacterial meningitis
WBC count
- high in bacterial
- viral = normal
- 80%PMN in bacterial
- 50%L & 20%PMN in viral
Protein
- much higher in bacterial
- viral = normal
Glucose
- lower in bacterial
- viral = normal - low
What treatment is given for meningitis?
Start appropriate IV antibiotics (e.g. cefotaxime) if any risk of bacterial meningitis
No evidence to support use of any specific treatment in viral meningitis (though some treat HSV and VZV with aciclovir)
Mainly supportive therapy (e.g. analgesia and antipyretics)
Generally good prognosis (but growing evidence of long term symptoms in some people, e.g. headaches, cognitive dysfunction)
NOTIFIABLE - inform local public health dept
What percentage of mumps cases develop meningitis?
10-30%
What is the relevance of HIV to meningitis diagnosis?
Meningitis can occur as part of primary infection
Associated features (= like glandular fever)
- Fever
- Lymphadenopathy
- Pharyngitis
- Rash
- Self-limiting symptoms
Important diagnosis not to miss
What is the most common cause of viral encephalitis?
HSV 1 in 90% of cases
What is the clinical presentation of viral encephalitis?
Major features:
- Altered mental state (confusion/bizarre behaviour -> coma)
- Fever
- Headache
- Meningism (may be absent)
+/- Focal neurology:
- Seizures
- Cranial nerve palsy
- Weakness
- Ataxia
- Dysphasia/aphasia
