Viral meningitis/encephalitis Flashcards
What is encephalitis?
Inflammation of the brain parenchyma - grey and white matter
What is meningo-encephalitis?
Inflammation of the brain and meninges
Are encephalitis and meningitis easily distinguishable clinically?
No
What is meant by aseptic meningitis?
1) Clinical picture of meningitis
2) White cell count above normal in CSF (>5x10^6/L)
3) Negative bacterial culture of the CSF
What are the most common cause of aseptic meningitis?
Viruses
Other than viruses name 7 other causes of aseptic meningitis?
1) Partially treated bacterial meningitis
2) Listeria
3) TB
4) Syphilis
5) Malignancy
6) Autoimmune conditions
7) Drugs
What is a virion
basic infectious particle
What is the simple structure of a virus?
1) Nucleic acid - may be DNA or RNA and single or double stranded with multiple or just one strand - linear or circular
2) Capsid - protein coat made up of capsomeres (subunits)
Other than the simple virus structure what other 2 things can some viruses contain?
1) Some have a lipid envelope (derived from host cell membrane as they bud off)
2) Some contain other proteins / enzymes
Give 3 possible functions of the enzymes found in some viruses?
1) Replicating genetic material
2) Influencing transcription (by host material)
3) Protein modification
In which group is viral meningitis most common, what are the 2 peaks of hospital admission?
Neonates and children
Peaks in:
1) Neonates
2) Aged ~5years
What is the incidence of viral meningitis per 100,000?
5-15 cases per 100,000
What kind of viruses are the leading cause of viral meningitis, give 5 examples of that kind?
Enteroviruses
1) Echoviruses
2) Coxsackie virus
3) Parecho viruses
4) Enteroviruses 70 and 71
5) Poliovirus
Other than enteroviruses what other group of viruses commonly cause viral meningitis?
Herpes viruses
Give 5 examples of herpes viruses which commonly cause viral meningitis?
1) Herpes simplex virus 2
2) Varicella zoster virus
3) Cytomegalovirus
4) HHV6, HHV7
5) Epstein barr virus
Does HSV1 or 2 more commonly cause viral meningitis?
HSV2
What is the name of the Japanese encephalitis virus?
Arboviruses
Other than enteroviruses and herpes viruses which 7 other viruses cause viral meningitis?
1) Mumps Virus
2) HIV
3) Adenovirus
4) Measles
5) Influenza
6) Parainfluenza type 3
7) Lymphocytic choriomeningitis virus (LCMV)
In what percentage of cases of viral meningitis is the cause unknown?
35%
What are the symptoms mainly attributable to in viral meningitis?
Bodies reaction to the virus - the inflammatory response in the CNS
What are the 4 steps in the pathogenesis of viral meningitis?
1) Colonisation of mucosal surfaces
2) Invasion of epithelial surface
3) Replication in cells
4) Dissemination and CNS invasion
What are the 3 modes of CNS invasion for viral causes of meningitis?
1) Via cerebral microvascular endothelial cells
2) Via choroid plexus epithelium
3) Spread along the olfactory nerve
What 3 symptoms make up meningism?
1) Headache
2) Neck stiffness
3) Photophobia
What are the 3 main features of a clinical presentation of viral meningitis?
1) Fever
2) Meningism (headache, neck stiffness, photophobia)
3) Sometimes viral prodrome (lethargy, myalgia, arthralgias, sore throat, D&V, rash)
What 6 features can be seen in a viral prodrome?
1) Lethargy
2) Myalgia
3) Arthralgia
4) Sore throat
5) D&V
6) Rash
How may the clinical presentation of viral meningitis differ in neonates/infants?
1) Meningeal signs may be absent
2) Look for nuchal rigidity (neck stiffness)
3) May see a bulging anterior fontanelle (from raised ICP)
What is Kernig’s sign (found on examination for meningitis)?
With hip and knee flexed at 90 degrees, the knee cannot be extended due to pain/stiffness in the hamstrings
What is Brudzinski’s sign (found on examination for meningitis)?
Flexing the neck causes the hips and knees to flex
What is nuchal rigidity?
Resistance to flexion of the neck
What blood tests would be carried out when investigating meningitis? 6
1) FBC
2) U&E
3) CRP
4) Clotting (need to know OK if going to do a LP)
5) Blood culture
6) Blood glucose (to compare to CSF glucose)
Why would a CT head be carried out in investigating viral meningitis?
To look for evidence of raised ICP (important to know if going to do a LP - and is therefore indicated before an LP in certain circumstances) and alternative diagnosis
What is the first investigation which should be carried out ideally?
Lumbar puncture
For what 4 reasons would a lumbar puncture be carried out in suspected viral meningitis?
1) Microscopy, culture and sensitivity (MC&S)
2) Protein
3) Glucose (must check blood glucose at the same time)
4) Viral PCR: enteroviruses, HSV, VZV
Why must a blood glucose be done when analysing the CSF glucose?
CSF glucose alone is irrelevant - needs to be compared to plasma glucose, without knowing the plasma glucose the CSF glucose can therefore not be interpreted
What is pleocytosis?
White cells in a fluid (here refers to white cells in CSF)
What are the CSF findings in viral meningitis in terms of white cells, protein and glucose?
White cell count - pleocytosis
Lymphocytic, usually less than 500 (as opposed to neutrophilic which would be more predominant in bacterial meningitis)
May initially be a predominance of neutrophils (first 24 hours)
Protein (0.2-0.4 g/L) - normal or mildly elevated (0.5-1.0)
Glucose (ratio of CSF: plasma - normal is 50-66%) - in viral meningitis is normal or slightly low
What are the CSF findings in bacterial meningitis in terms of white cells, protein and glucose?
White cells - higher in bacterial (100-20,000)
>80% PMC (pleomorphic cells - neutrophils)
Protein raised
Glucose reduced
Other than CSF and blood cultures what 2 other microbiological investigations could be carried out in suspected viral meningitis, what viruses would they be looking for?
1) Throat swan and/or stool sample
- Enterovirus PCR
2) Serology
- Mumps, EBV/CMV, HIV, Other viruses as indicated eg. travel related
What is the treatment for viral meningitis - what treatment should be started straight away?
Start appropriate IV Abx (eg. cefotaxime) if any risk of bacterial meningitis
Mainly supportive therapy (eg. analgesia and anti-pyretics)
(Also a notifiable disease)
What anti-viral is sometimes used to treat viral meningitis, is there any research to support its use?
Aciclovir (in HSV and VZV) - but no evidence to support use of any specific treatment
What is the prognosis of viral meningitis?
Generally good - although growing evidence of long term symptoms in some people eg. headaches and cognitive dysfunction
What is the commonest cause of viral meningitis in the UK, what seasonal epidemics are seen?
Enteroviral meningitis
Classically late summer/autumn epidemics
In addition to the general presenting symptoms in meningitis what 5 other symptoms are common in enteroviral meningitis?
1) Fever
2) Vomiting
3) Anorexia
4) Rash
5) Upper respiratory tract infections
What is the treatment and prognosis for enteroviral meningitis?
No specific treatment
Full recovery is normal
What are the 2 forms of herpes simplex virus and what does each commonly cause?
1) HSV1 - causes cold sores and viral encephalitis
2) HSV2 - causes genital herpes and meningitis
What is the 2nd most common cause of viral meningitis?
HSV2
When does HSV2 viral meningitis commonly occur in relation to the primary infection with HSV2?
Can follow the primary infection (3-12/7 after genital lesions)
Or can occur during/between relapses
Is there any specific treatment for HSV2 viral meningitis?
Aciclovir is sometimes used but there is not evidence to suggest that its effective
What is Mollaret’s meningitis?
Recurrent aseptic meningitis
What is the cause of Mollaret’s meningitis?
Major causes is HSV2
What primary and secondary diseases does the varicella zoster virus cause?
Primary - chicken pox
Secondary - shingles
Is meningitis caused by VZV common?
Unusual but can occur during chicken pox, shingles or on its own or after vaccination
Is there any specific treatment for VZV meningitis?
Aciclovir sometimes used but no evidence that it is effective
What is the prognosis of VZV meningitis?
Complete recovery is normal
What percentage of cases of mumps lead to mumps meningitis?
10-30%
How long after parotitis do the CNS symptoms of mumps meningitis present?
5 days
In addition to the general symptoms of meningitis what 2 other symptoms are common in mumps meningitis?
1) Abdominal pain
2) Orchitis (inflammation of testicles)
Is there any treatment for mumps meningitis?
No specific treatment but an available vaccine
What is the prognosis of mumps meningitis?
Full recovery is normal
HIV is another cause of viral meningitis when in the course of infection does this tend to occur?
As part of the primary infection
What are the 4 associated features of HIV meningitis?
1) Fever
2) Lymphadenopathy
3) Pharyngitis
4) Rash
Is there any treatment for HIV meningitis?
No - the symptoms are self-limiting
What is the most common cause of viral encephalitis?
Herpes simplex virus 1 and 2
90% of cases are HSV1
Other than HSV what are the 11 other viral causes of viral encephalitis?
1) VZV
2) EBV
3) CMV
4) Measles
5) Mumps
6) Enteroviruses (including polio)
7) Arboviruses
8) Influenza
9) Rubella
10) HIV
11) Rabies
Other than viral causes what are the 5 other causes of encephalitis?
1) Bacteria (strep pneumonia, Neisseria meningitidis, TB)
2) Malignancy (paraneoplastic)
3) Autoimmune
4) Acute disseminated encephalomyopathy (ADEM)
5) Other immune-mediated
In what percentage of cases of encephalitis is the cause unknown?
37%
What are the 4 major features of the clinical presentation of encephalitis?
1) Altered mental state (confusion/bizarre behaviour - coma)
2) Fever
3) Headache
4) Meningism (may be absent)
Focal neurology may also be present in encephalitis, give 5 examples?
1) Seizures
2) Weakness
3) Dysphasia/aphasia
4) Cranial nerve palsy
5) Ataxia
What 5 investigations would be carried out in encephalitis?
1) Blood tests
2) CT - likely to be necessary before LP
3) MRI - may see changes typical of HSV encephalitis (temporal lobe affected)
4) Lumbar puncture
5) EEG
What blood tests would be important in investigating encephalitis? 6
1) FBC
2) U&E
3) CRP
4) Clotting
5) Blood cultures
6) Serology
What 4 investigations would be carried out on the CSF in encephalitis?
1) Microscopy
2) Culture and sensitivity
3) Protein/glucose
4) Viral PCR
What would an EEG show in 75% of cases of HSV encephalitis?
Abnormal temporal lobe activity
Do the CSF findings in viral encephalitis and viral meningitis differ?
No, they are the same
What is the treatment for viral encephalitis?
High dose IV acyclovir (10mg/kg tds) for 14-21 days
Start the treatment on clinical suspicion, don’t wait for test results
Oral switch should be avoided
Should steroid be used in viral encephalitis?
No, there is insufficient evidence to recommend them
How common is herpes simplex encephalitis, who is it most common in?
Rare
Bimodal distribution - increased incidence 50 years and equally spread through the sexes
What is the prognosis for HSE?
High mortality if left untreated - 70%
Mortality if treated still remains high - 28% at 18 months
How does HSE infect the brain tissue and cause encephalitis?
There is direct transmission of the virus along the neural/olfactory pathways
Virus then gets reactivated in the trigeminal ganglia
Get acute focal necrotising encephalitis
Leads to inflammation of brain tissue
What finding in HSE is an indicator of poor prognosis and what improves the outcome?
If GCS
Survivors of HSE can suffer what 3 common long lasting effects?
1) Paralysis
2) Speech loss
3) Personality change
What is acute disseminated encephalomyelopathy? (ADEM)
Immune mediated CNS demyelination
What is the link between ADEM and viral infection?
The condition although immune mediated can follow a viral infection or vaccination
Why is ADEM difficult to distinguish from viral encephalitis, what investigation can be helpful in doing so?
CSF findings and clinical presentation are the same as viral encephalitis
MRI can be useful
What is the treatment for ADEM, is recovery common?
Steroids or other immunosuppressants
Recovery is variable
