CNS Infections Flashcards
What is meningitis?
infection of the meninges
What is encephalitis?
inflammation of the brain parenchyma - cerebral cortex is diffusly involved
What are the features of pyogenic meningitis?
PUS FORMING
lots of neutrophils in the subarachnoid space
over the leptomeninges on the surface of the brain
What are the features of viral meningitis?
often late summer/autumn
often due to enteroviruses (ECHO etc)
How is viral meningitis diagnosed?
stool PCR
throat swab PCR
CSF PCR
What is the most common pathogen for bacterial meningitis for neonates?
listeria
group B strep
E. coli
What is the most common pathogen for bacterial meningitis for children?
H. influenza
What is the most common pathogen for bacterial meningitis for ages 10-21?
nisseria meningitidis
What is the most common pathogen for bacterial meningitis for ages >21?
strep pneumoniae > n.meningitidis
What is the most common pathogen for bacterial meningitis for ages >65?
strep pneumoniae > listeria
What are the risk factors for bacterial meningitis?
decreased cell immunity
neurosurgery/head trauma
fracture of the cribiform plate
CSF shunt
What are the complications that come from bacterial meningitis?
purulence - clusters around nerves and the bottom of the brain
invasion - pia prevents meningitis becoming an abscess
cerebral oedema
ventriculitis/hydrocephalus
What is the pathophysiology of bacterial meningitis?
nasopharyngeal colonisation
direct extension of bacteria - from across skull defects/fractures or parameningeal foci
from remote foci of infection - endocarditis, pneumonia, UTIs
What are the characteristics of nisseria meningitis?
found in the throats of healthy carriers causes meningococcal meningitis (most deadly form) usually in young children travels through the blood stream can vaccinate against it
What are the characteristics of H.influenzae?
part of normal throat microbia
type b is most common - in children under 4
can vaccinate against it
What are the characteristics of strep pneumoniae?
found normally in the nasopharynx
can vaccinate against it
common to occur in hospitalised patients, patients with CSF skull fractures, diabetics and young children
What are the characteristics of listeria monocytogenes?
mainly bacteraemic illness
gram positive bacilli
common in neonatal and >55 years, or immunosuppressed
What additional antibiotic must you give for listeria monocytogenes bacterial meningitis?
amoxicillin IV
What are the characteristics of tuberculous meningitis?
occurs due to reactivation or in the elderly
previous TB on CXR
What is the treatment for tuberculous meningitis bacterial meningitis?
4 RIPE 2 RI
What are the characteristics of cryptococcal meningitis?
aseptic picture on CSF as it is a fungal
mainly in HIV patients
CD4 <100
What is the treatment for cryptococcal meningitis bacterial meningitis?
IV Amphotenicin
What are the clinical signs of bacterial meningitis?
neck stiffness photophobia fever altered conciousness non blanching rash lethargy
How is bacterial meningitis diagnosed?
lumbar puncture - BUT MUST DO CT FIRST IF THEY HAVE SIGNS OF A FOCAL DEFICIT ETC do 4 tubes: 1 tube haematology 1 tube microbiology 1 tube chemistry 1 tube haematology
What CSF signs are indicative of bacterial meningitis?
WBC count > 2,000
neutrophils > 1180
protein > 220
glucose >34
What is the treatment of bacterial meningitis?
IV ceftriaxone and dexamethasone
When would you not give dexamethasone in bacterial meningitis?
if immunocomprimised, septic shock or meningococcal
What is the treatment of bacterial meningitis in a penicilin allergic patient?
chloramphenicol and vacomycin IV
What is a common cause of encephalitis?
HSV 1 and 2 - treat with acliclovir
How does encephalitis present?
stupor coma seizures confusion partial paralysis psychosis speech and memory problems
What is the presentation of meningo-encephalitis?
headache
fever
neck stiffness
PLUS features of encephalitis
