CNS infections Flashcards
Define Meningitis
inflammation of the meninges
Define encephalitis
inflammation of the brain
Define myelitis
inflammation of the spinal cord
Deine neuritis
inflammation of the peripheral nerves
Name 4 routes of meningitis infection
Blood borne
Parameningeal supparation ( otis media, sinisitis
Direct spread through defect in the dura (surgery or trauma)
Direct spread though cribiform plate (rare)
What characteristics of the CSF make it unusual to treat
Low protein/complement
Low IgG
no lymphatics
BBB
How does bacteria get into the blood stream from the naspharynx
IgA protease
pili
endocytosis
separate tight junctions
In the blood how does the bacteria avoid attack
Capsules resistlysis/phagocytosis
In the CSF how does bacteria avoid the immune system
no ig C3/4 or professional phagocytes
Once in the CSF what does the presence of bacteria trigger
Mononuclear and glial cells
migration of neutrophils- release of cyto-toxic oxygen metabolites
cerebral capillary endothelium so allow entry of plasme proteins = oedema
What are meningism symptoms
Global severe headache
neck and back stiffness
nausea and vomiting
photophobia
What are some physical signs
Fever ( also can be low )
rash-purpuric/petechial in menginococcal but also streptococcal, hib spp and enterovrius
What is the constellation of symptoms in bacterial meningitis
97% fever 82% meningism 66% impaired consiousness 52% rash 30% seizures
For an adult what symptoms suggest they have a more than 50% chance of death or permanent damage
Hypotension
serizures
and altered consiousnes
What signs of bacterial meningitis are specific to children
Flaccid or later opisthotonus
bulging fontanelle
strange cry
convulsions
What is the most rapid diagnostic test for bacterial meningitis
Lumbar puncture but there is a risk of herniation with raised ICP
When is a CT scan indicated
When the diagnosis is in doubt
with focal abnormalities
with coma or seizures
Name 6 causes of lymphocytic CSF
TB partially treated bacterial infection intracranial abcesses Leptospirosis Lyme borreliosis Viral meningo-enceohalitis syphillis lymphocytic leukaemias
What tests can be done on CSF for menigitis
Gram stain
Zn
Agglutination
PCR
Name 6 organisms that cause bacterial meningitis
Neisseria meningitidis streptococcus pneumoniae Heamophilus influenzae type B group B streptococcus e.coli listeria monocytogenes
Which bacteria are most likely to affect children and young adults
n. meningitidis
Which bacteria are likely to affect neonates
Group B streptococcus
e.coli
Listeria monocytogenes
Which bacteria is it unlikely to be now because of vaccination
Heamophilus influenzae type B
Which bacteria are you worried about in the elderly and children under 2
streptococcus pneumoniae
What are the predisposing factors or pnuemococcal meningitis
Alcohol, diabetes, immunocompromised, hyposplenism, myeloma
What are characteristic signs of pneumococcal meningitis
Pneumonia +/- otis media in 50%
neurological signs, seizures and imparied consiousness
What gram stain is listeriosis
negative
What characterises listeriosis
Effets brainstem, ataxia and movement disorders
What are the complications of meningitis
Death subdural collection cerebral vein thrombosis hydrocephallus deafness convulsions visual/motor/sensory deficits
What are the management strategies for meningitis
Antibiotics oxygen decrease ICP prevention of hypoglycaemia and hyponatreamia anticonvulsants
For which meningitis are steroids indicated
Hib species
When is chemoprophylaxis indicated
Hib and meningococcal for kissing or household contacts
What can myelitis cause
transverse- acute transection of the spinal cord
What are some causes of myelitis
vasculitis of anterior spinal artery- primary infection=VZV TB Syphilis
post infection=measels mumps rubella
direct invasion of cord= VZV borrelia HTVL-1
What are some symptoms of myelitis
Flaccid paralysis, sensory loss
What are some symptoms of encehalitis
irritability altered personality drowsiness cerebral/brainstem failure ataxia excessive brisk tendon reflexes sluggish pupil reflexes signs of brain swelling
What causes primary encephalomyeltis and what is their entry to the body
HSV-1 mucosa
enteroviruses gi tract
listeria gi tract
measels and mumps resp tract
What things cause encephalomyelitis post infection
Chicken pox
flu A+B
measels
How do you treat HS encephalitis
aciclovir
How do you treat most viral mengintis
self-limting, so only supportive treatment
Comparing bacterial, viral and TB mengitis what is the difference in
a) predominant cell
b) cell count
c) protein
d) glucose
a) bacterial =polymorphs and viral and tb = lymphocytes
b) high cell count, slight to mod, mod to high
c) high, normal/raised, high
d) low, normal/low, low
Other than cellular picture of CSF what indicates bacterial rather than viral meningitis
systemic inflammation ( CRP marker) rash
What is the commonest cause of viral meningitis
Enterovirus
What antibiotics are mostly used for bacterial menginitis
a) in adults
b) neonates
a) Cefriaxone + amoxycilin if listeria?
b) benzylpenicillin and gentamicin
