CNS infections Flashcards
histological appearance of bacterial meningitis
neutrophils in subarachnoid space
common viruses which cause meningitis
enteroviruses (eg ECHO)
herpes simplex
varicella zoster
paramyxovirus
how to diagnose viral meningitis
viral stool culture
throat swab
CSF PCR
treatment of viral meningitis
Supportive therapy - it is self-limiting
if viral meningitis, what else should be tested for
HIV
if HSV, test for other sexually transmitted diseases
encephalitis is usually bacterial/viral
viral - HSV1+2 most common
clinical features of encephalitis
meningism odd behaviour/confusion low GCS/coma fever headache focal neurological symptoms/seizures PRECEDED BY SYMTPOMS OF INFECTION
investigations for encephalitis
blood cultures (including toxoplasma IgM titre and malaria film)
lumbar puncture (increased protein and lymphocytes, decreased glucose, send for PCR)
EEG
MRI - inflamed portion of temporal lobe
Start treatment immediately/after lab results in encephalitis
immediately
treatment for viral encephalitis
If herpes/varicella, IV acyclovir for 14 days then repeat lumbar puncture
continue until PCR is negative
common bacterial organisms in neonates
listeria
group B strep
Ecoli
common bacterial organism in children
H influenza
common bacterial organism age 10-21
Neisseria meningitidis
common bacterial organism >21
strep pneumonia
can be Neisseria meningitides
common bacterial in ?65
strep pneumonia
can be listeria
bacterial organism if cell mediated immunity (e.g. neonatal, immunosuppressed, malignancy)
listeria monocytogenes
S. pneumoniae
N. Meningitidis
aerobic GNR
bacterial organism if neurosurgery/head trauma/CSF shunt
S. Aureus
S. epidermidis
aerobic GNR
bacterial organism if fracture of cribiform plate
strep pneumonia
H influenza
beta-haemolytic strep group A
most common organisms causing meningitis
meningococcus (Neisseria meningitides)
pneumococcus (strep pneumoniae) - MOST COMMON
where does Neisseria meningitides usually reside
throats of healthy carriers - gets to meninges through bloodstream
what meningitis organisms have a prophylactic vaccination
Neisseria meningitides
H influenza
Strep pneumoniae
clinical presentation of tuberculous meningitis
non-specific ill health with previous TB on CXR
treatment for TB meningitis
isoniazid and rifampicin
add pyrazinamide and ethambutol later
early clinical signs of bacterial meningitis
headache
leg pins
cold hands and feet
abnormal skin colour
signs of meningism
neck stiffness
photophobia
Kernig’s sign (pain and resistance on passive knee extension with hip fully flexed)
late clinical features of bacterial meningitis
meningism decreased consciousness seizures/focal neurological signs petechial rash (non-blanching) pyrexia
treatment should be started immediately/after culture results in meningitis
immediately
immediate action in suspected bacterial meningitis
ceftriaxone IV and Dexamethasone IV immediately AFTER blood cultures are taken
when is lumbar puncture contraindicated
suspected ICP
uncorrected coagulopathy
acute spinal cord trauma
severe sepsis/rapidly evolving rash
what antibiotic should be used if penicillin allergic
chloramphenicol IV + vancomycin IV
what antibiotic should be added if listeria cover is required
amoxicillin/ampicillin IV
if recent travel in last 6 months, what antibiotic should be added
vancomycin or rifampicin
what organism should dexamethasone be continued for
pneumococcal
what time of year is viral meningitis common
late summer/autumn
later tests in meningitis
throat swab
culture rash
CT if papilloedema/focal neuro signs
lumbar puncture if feasible
Results of CSF culture in meningitis
neutrophils and protein increased
low glucose
what does N meningitidis look like histologically
gram negative coffee bean shaped diplococci
what does S pneumoniae look like histologically
gram positive lanceolate diplococci appearing in short chains
H influenzae on gram stain
pleomorphic gram negative rods
why might meningitis be ‘culture negative
pre-lumbar puncture use of oral antibiotics for a different infection
what empirical antibiotic if penicillin allergy and listeria cover required
co-trimoxazole
when should steroids be avoided
post surgical meningitis
severely immunocompromised
meningoccal/septic shock
hypersensitive to steroids
what are the contact prophylaxis regimens for bacterial meningitis
600 mg rifampicin orally 12-hourly for 4 doses
OR
500mg ciprofloxacin orally as a single dose
consequences of untreated infection
brain herniation and death
cord compression and necrosis - permanent paralysis
complications of meningitis
purulence - clusters at base of brain, exudate around nerves (3 and 6 particularly vulnerable)
invasion - abscesses
cerebral oedema
ventriculitis/hydrocephalus
