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CNSLF Micro - Viral Infections + Prions in CNS (i) (Non-polio…
CNSLF Micro - Viral Infections + Prions in CNS (i)
Intro
meningitis classic symptoms
moreso in older children + adults
fever
headache
neck stiffness
vomiting
photophobia
irritability
confusion/reduced consciousness
seizures
dura fixed to inside of cranium - doesn't get inflamed
baby's heads can cope with raised ICP (head can expand as fissures not fused)
encephalitis affects normal brain function
altered mental status
motor or sensory deficits
behaviour or personality changes
speech or movement disorders
seizures
Viral CNS infections intro
can be part of a generalised infection (e.g. polio)
may solely affect the CNS
may present some time after the initial presenting infection (e.g. SSPE yrs after measles)
some a/w congenital damage to CNS
rubella
CMV
zika virus (microcephaly)
after primary multiplication in other sites (e.g. GIT for enteroviruses) the virus may reach the CNS
via bloodstream (usual route for enteroviruses)
along N pathways: rabies, HSV
through the olfactory mucosa
CNS pathology caused by viruses
virus multiplication + resultant cellular damage
host immune response (cellular immune response + cks)
Viral meningitis
more common than bacterial but tend to be more self-limiting (v severe headache)
causes
enteroviruses (echoviruses, coxsackie B, enterovirus 71) are the most common
herpes (e.g. HSV, VZV - wks after)
mumps
preventable with MMR
arboviruses (e.g. west nile virus, Japanese encephalitis)
Classic presentation
fever
headache
neck stiffness
vomiting
photophobia
not usually as sick as bacterial
symptoms usually evolve more slowly than bacterial (several days)
may be clinically indistinguishable from bacterial
CSF
typically clear + colourless
WCC elevated (lymphocytes - mononuclear cells)
protein elevated
glucose normal
bacterial culture -ve - aka aseptic meningitis
PCR
enteroviruses RNA
HSV DNA
VZV DNA
dDx for a lymphocytic response in CSF
leptospirosis
syphilis
lyme disease
cryptococcosis
toxoplasmosis
TB (preventable with BCG)
malignant infiltration of meninges
connective tissue diseases
partially antibiotic tx bacterial meningitis
Tx
excl neonatal period, usually mild + self-limiting
supportive: rest, hydration, antipyretics
seizure management
unclear whether acyclovir is of benefit in HSV meningitis (NB to differentiate from HSV encephalitis which must be txed with acyclovir)
Non-polio enteroviruses
most common pathogens in viral meningitis
subtypes causing meningitis
echovirus
coxsackie B
enterovirus 71
mainly affect infants + young children
Usually mild + self-limiting but can cause serious illness in neonates
peak activity: late spring-autumn
human only reservoir, transmission mostly faecal oral
multiply in GIT but only occasionally cause GI symptoms
enter bloodstream (viraemia) - hence infection in many organs (inlc CNS)
enterovirus 71 also a/w encephalitis (esp in East + SE Asia)
enterovirus D68 possible a/w acute flaccid paralysis following resp illness
note: enteroviral infections are v common + other cause other symptoms not inviting CNs...
fever + rash
myocarditis, pericarditis (coxsackie, echoviruses)
hand, foot + mouth disease (Coksackie virus, enterovirus 71)