viral meningitis and encephalitis Flashcards
what does “itis” mean
inflammation
define meningitis
inflammation of the meninges
define encephalitis
inflammation of the brain
define menigo-encephalitis
inflammation of the meninges and the brain
define aseptic meningitis
white cell count in CSF >5x 10^6/L
negative bacterial culture
commonest causes of aseptic meningitis
viral- most common
partially treta bacterial meningitis (so culture is negative but WBC is high).
Malignancy
Autoimmune conditions and drugs, Listeria, TB, Syphilis.
most common cause of viral meningitis
unknown-37%
Enterovirus
Herpes simplex virus
most common enetroviruses to cause viral encephalitis
Echovirus, coxsackie virus, parencho virus, enterovirus and polio
most common herpes virus to cause viral encephalitis
HSV1, HSV2 , varicella zoster
how doe pathogens cause viral meningitis
colonise mucosal surfaces
invade epithelial cells
replicate cells
disseminate and CNS invasion
how do pathogens invade the CNS
cerebral microvascular endothelial cells
choroid plexus epithelium- bloodstream.
spread along the olfactory nerve.
clinical features of viral meningitis.
fever, meningism, viral prodrome (lethargy, myalgia’s, arthralgia’s, sore throat ), diahorrhea and vommitting and rash.
what is meningism (what 3 symptoms does it involve`0
headahce, neck stiffness and photophobia
clinal features of viral meningitis in children
nuchal rigidity (neck stiffness), bulging anterior frontelle.
what 3 examinations are carried out on suspected patients with viral meningitis
kernigs sign
Brudzinskis sign
nuchal rididity
what is Kernigs sign
hip and knee flexed at 90, knee cannot be extended due to pain and stiffness in hamstrings.
what is Brudzinski’s sign
flexing neck causes hips and knees to flex at it reduces stretch on spinal cord and meninges
what blood investigations are carried out in viral meningitis
Blood test- FBC, U and E, CRP, clotting (before LP), blood culture, renal function (dehydration).
why might a CT be used in viral meningitis
look for raised intracranial pressure and other diagnosis of mass, lesion, subarachnoid haemorrhage.
why should a lumbar puncture not be carried on a patient with raised intracranial pressure.
removing the CSF can cause the brain to herniate through the foramen magnum
when should a lumbar puncture be carried out on a patient with suspected viral meningitis
ASAP
before antibiotics and CT
within 1 hr of admission.
what can the CSF obtained from a lumbar puncture be used for
– Microscopy, culture and sensitivity (MCS)
– Protein
– Glucose (CSF and blood glucose)
– Viral PCR
what is the WBC in bacterial meningitis
100-20,000 mm ^2
what is the WBC in viral meningitis
5-500 mm^2
what is the glucose level in bacterial meningitis
what is the glucose level in viral meningitis
30-70 mg/dL
what is the protein level in bacterial meningitis
100-500 mg/dL
what is the protein level in viral meningitis
30-150 mg/dL
what microbiological investigations other than those obtained from CSF can be undertaken for viral meningitis
throat swab, stool sample
serology- Mumups, EBV/CMV/HIV
what is the treatment for viral meningitis
Mainly supportive therapy (e.g. analgesia and antipyretics)
no antibiotics unless bacterial where you give IV cefotaxime.
some treat HSV/VZV with aciclovir
is viral meningitis a notifiable condition
Yes
Commoest cause of meningitis in the UK is
enterovirus
what is the prognosis of enetrrovirus caused viral meningitis
full recovery.
common symptoms of enterovirus infection
fever, vomitting, anorexia, rash, upper respiratory tract symptoms.
what condition does HSV1 infection cause
encephalitis (cold sores)
what condition does HSV2 infection cause
meningitis (genital herpes)
define mollaret’s meningitis and what organism causes it
recurrent aseptic meningitis and wide differential but major cause= HSV2
what does primary infection of VSV cause
chickenpox
what does secondary infection of VSV cause
shingles
does viral meningitis occur during chickenpox and shingles to not
most commonly not, but it can occur with it.
aciclovir is not used in what 2 pathogen caused viral meningitis
HSV and VZV
when do CNS symptoms in mumps meningitis
5 days after onset of parotitis
clinical features of mumps meningitis excluding for CNS symptoms
abdominal pain
Orchitis- inflammation of the testes
prevention of Mumps meningitis
vaccine
when does HIV meningitis occur
part of primary infection
clinical features associated with HIV meningitis
glandular fever Fever Lymphadenopathy Pharyngitis Rash
what causes viral encephalitis
unknown-37%
herpes- HSV1
can be bacterial-
acute disseminated encephamyophaty (damages myelin)
what part of a history is key to encephalitis and meningitis
travel history
clinical presentation of encephalitis
Major features- low GCS.
Altered mental state (confusion, bizarre behaviour and even coma)
Fever, headache, meningism (may be absent)
+/- Focal neurology
Seizures, weakness, dysphasia, aphasia, cranial nerve palsy and ataxia.
Neuroexamination needed and get a collateral history from friend or relative to ask if they have noticed any confusion in the patient.
what investigations are carried out for viral encephalitis.
blood test- – FBC, U&E,CRP, clotting, (Blood cultures), Serology
CT – likely to be necessary before LP- due to low GCS score focal neurology will need to be checked.
MRI – may see changes typical of HSV encephalitis Lumbar puncture: – Microscopy – Culture and sensitivity – Protein/glucose – Viral PCR
EEG: In HSV encephalitis 75% will show abnormal temporal lobe activity
In HSV encephalitis 75% will show abnormal activity in which lobe of the brain, what investigation is used to prove this
temporal lobe
EEG-electroencephalogram
What is the treatment for viral encephalitis.
• High dose IV aciclovir
o 10mg/kg tds
o 14-21 days
why is oral switch of acicolovir not recommended
long time period over which drugs might have to be taken.
what is the bimodal distribution of herpes encephalitis
50 yrs.
what signs are present in the neurological sequel of herpes encephalitis
– Paralysis
– Speech loss
– Personality change
what is the pathogenesis of herpes in causing viral encephalitis.
o Direct transmission of the virus along neural/olfactory pathways
o Reactivation in the trigeminal ganglia (HSV1)
Is herpes simplex encephalitis more common on primary infection or reactivation
primary
define Acute focal necrotising encephalitis
brain tissue dies, increased ICP and increased Inflammation.
what pathogenic organism infection causes Acute focal necrotising encephalitis
herpes simplex
define Acute disseminated encephalomyelopathy
AUTOIMMUNE
immune mediated CNS demyelination
can follow viral infection or vaccine
what investigation is useful in (ADEM) Acute disseminated encephalomyelopathy
MRI
what is the main treatment for Acute disseminated encephalomyelopathy (ADEM)
Steroids and immunosuppression.
