CNS Infections Flashcards
important microbes to know about?
pneumococci
meningococci
untreated CNS infection has what risks?
brain herniation and death
cord compression and necrosis and subsequent permanent paralysis
classification of meningitis?
acute pyogenic (bacterial)
acute aseptic (e.g viral) meningitis
acute focal suppurative infection (abscess, subdural and extradural empyema)
chronic bacterial infection (tuberculosis)
acute encephalitis (infection in brain parenchyma)
aseptic meningitis?
no bacteria involved but same symptoms as meningitis
can be viral
pyogenic meningitis shows what?
“pus forming”
shows thick layer of suppurative exudate over leptomeninges on surface of brain
exudate in basal and convexity surface
microscopic features of pyogenic meningitis?
lots of neutrophils in subarachnoid space
general rule for meningitis antibiotics?
always very high doses IV (never oral)
ceftriaxone 2g IV (or chloramphenicol if penicillin allergic)
- add vancomycin in places where it is known there are resistant meningococcus
when does viral meningitis usually occur during the year?
late summer/autumn
what causes viral meningitis?
enteroviruses (e.g ECHO virus)
other microbes and other non-infectious causes as well
how is viral meningitis diagnosed?
viral stool culture
throat swab
CSF PCR
how is viral meningitis managed?
supportive (self limiting)
encephalitis features?
cerebral cortex is diffusely involved mental status change confusion obtundation, stupor or coma behavioural, memory and speech disturbance focal or diffuse insidious onset meningismus (neck stiffness) seizures, partial paralysis
important differential for encephalitis?
herpes simplex virus
look at flow charts for meningitis management
…
encephalitis findings on MRI?
shows as diffuse white areas
- HSV encephalitis usually in temporal lobe
main features of bacterial meningitis?
fever rash photophobia change in mental state nausea and vomiting
main causes of bacterial meningitis depending on age?
neonates = listeria group B strep, E.coli children = H influenzae 10-21 = Neisseria meningitidis 21+ = strep pneumoniae > Neisseria meningitidis 65+ = strep pneumoniae
risk factors for bacterial meningitis?
immunocompromised
basilar skull fracture or fracture or cribiform plate
head trauma or post neurosurgery
CSF shunt
impact of meningitis after infection/
can cause death
25% of people have life changing after-affects (limb loss, blindness, paralysis, cerebral palsy etc)
complications?
purulence (pus collects at base of brain and around nerves and in sulci)
invasion
cerebral oedema
ventriculitis/hydrocephalus
3 main routes of infection in bacterial meningitis?
nasopharyngeal colonization
direct extension of bacteria (brain abscess, across skull fracture etc)
from remote foci of infection (endocarditis, pneumonia etc)
principles of lumbar puncture?
only perform in clinically feasible be cautious if increased ICP possible use sitting position if needed measure opening pressure if fast flow be careful in delirium treat with antibiotics first CSF pleocytosis not bacterial meningitis
what tests are performed on lumbar puncture sample?
haematology (cell count etc)
microbiology (gram stain, culture)
chemistry (glucose, protein)
microbiological diagnosis of meningitis?
microscopy biochemistry culture antigen detection PCR
bacterial meningitis can be culture negative, true or false?
true
10-15% are negative due to pre-lumbar puncture antibiotics
acute bacterial meningitis findings?
\+ve gram stain \+ve antigen detection high protein low glucose raised WBC and neutrophils
features of Neisseria meningitidis (meningococcal meningitis)?
found in throat gains access to meninges via blood stream may be found in leukocytes in CSF symptoms arise due to endotoxin most common in young kids
describe haemophilus influenzae meningitis?
part of normal throat microbiota
requires blood factors for growth
type B = most common cause of meningitis in kids <4
has a vaccine
strep pneumoniae meningitis?
found in nasopharynx
common in hospitalized, skull fractures, diabetics/alcoholics and young children
can be 2ndary to pneumococcal pneumonia in some cases
common causes of meningitis in immunocompromised?
listeria monocytogenes
mycobacterium tuberculosis
nocardia asteroids
Cryptococcus neoformans (HIV with CD4<100)
listeria is resistant to what antibiotic? how is it managed instead?
ceftriaxone
management = IV ampicillin/amoxicillin
describe listeria monocytogenes?
gram +ve bacillus
sporadic but becoming more common
neonatal, over 55s or immunosuppressed
describe tuberous meningitis?
often due to reactivation in the elderly non-specific ill health previous TB on CXR poor yield from CSF high morbidity if untreated
how is tuberous meningitis managed?
Isoniazid + rifampicin key
add pyrazinamide + ethambutol
cryptococcal meningitis features and management?
fungal
mainly in HIV
CD4 < 100
subtle presentation and aseptic CSF picture
management = IV amphotericin B/flucytosine, fluconazole
what is aseptic meningitis?
term used to describe non-pyogenic meningitis spinal fluid formula typically has - low WBC - minimally elevated protein - normal glucose
infectious causes of aseptic meningitis/encephalitis syndrome?
HSV 1 and 2 syphilis listeria tuberculosis Cryptococcus
non-infectious causes of aseptic meningitis?
carcinomatous sarcoidosis vasculitis dural venous sinus thrombosis migraine drugs
contact prophylaxis regimes to prevent meningitis if you’ve come into contact with someone?
600mg rifampicin orally every 12 hours for 4 doses (age 12+)
10mg/kg rifampicin every 12 hrs for 4 doses (3-11 months)
or
500mg ciprofloxacin orally as single dose
or
250mg ceftriaxone intramuscularly as single dose
how are secondary cases of meningitis prevented?
phone public health
keep GP records of all close contact to people with meningitis
indications for hospital admission?
signs of meningeal irritation impaired conscious level petechial rash febrile/unwell and has a recent fit illness after contact with someone with meningitis
what action should be taken on admission to hospital?
blood cultures
give treatment
take a throat swab
disrupt and swab or aspirate any petechial or purpuric skin lesions for microscopy and culture
who should receive a lumbar puncture?
all adult patients with suspected meningitis except when there is a clear contraindication or if there is a clear clinical diagnosis
are antibiotics given before or after lumbar puncture?
before
empirical antibiotic therapy?
2g IV ceftriaxone bd
- add IV ampicillin/amoxicillin 2g if listeria suspected
- penicillin allergy = chloramphenicol IV + vancomycin IV
- listeria + penicillin allergy = co-trimoxazole
how are steroids used in meningitis?
give to all patients with suspected bacterial meningitis before or with first dose of antibiotics
- don’t give in post-surgical, immunocompromised or septic shock
which causes of meningitis have vaccines?
Neisseria meningitidis (YWCA)
haemophilus influenzae
strep pneumoniae
