Meningitis Flashcards
what is bacterial meningitis
bacterial infection of the meningeal space
can happen due to a variety of bacteria
severe life-threatening illness
what is the pathophysiology of bacterial meningitis
invasion by bacteria leads to inflammation, caused by an immune reaction created by neutrophils
leads to elevated intracranial pressure
inflammation and thrombosis in arteries, can lead to ischaemia and stroke
damage to cranial nerves, can lead to deficits such as deafness
what is the common microbiology of bacterial meningitis
most cases are due to three organisms;
Neisseria meningitidis (meningococcus), often the cause of epidemic outbreaks
streptococcus pneumonia (pneumococcus)
Haemophilus influenza
what are other causes of bacterial meningitis
listeria monocytogenes - common in older adults, diabetic patients and pregnancy
infection can also seed from other sites (eg staphylococcus aureus due to a skull fracture)
what are the meninges and what is their function
connective tissue coverings
surround the brain and provide support and stability
what makes up the meninges
dura - hard, outer layer
arachnoid - spiders web appearance, major blood vessels run in subarachnoid space
pia - thin layer closest to brain tissue
what are the clinical features of meningitis
acute headache (typically develops over hours)
meningism - neck stiffness, photophobia
fever
non-blanching rash (meningococcus)
confusion, reduced consciousness
sometimes seizures
what would you see on a positive meningitis exam
stiff neck, Kernig’s and Brudzinski’s sign (lack sensitivity, often not present)
think meningitis in anyone with fever and headache
how is meningitis diagnosed
CSF sampling via lumbar puncture
lp should not be performedbefore CT if reduced consciousness and focal signs (if these are present there is a risk of herniation)
blood culture
can do blood PCR test (meningococcus)
what is tested in the csf sample when diagnosing meningitis
microscopy
culture and sensitivity testing
glucose and protein
additional testing that may be required (PCR, virology, other infections)
what is the CSF interpretation for bacterial meningitis
high pressure
cloudy/turbid appearance (even pus)
WBCs 1000-5000 polymorphs x10^6/L
low glucose
high protein
bacteria found on gram stain and culture
what is the CSF interpretation for viral meningitis
normal pressure
clear appearance
10-2000 lymphocytes x10^6/L
normal glucose
normal, sometimes high protein
sometimes virus appears on PCR
what is the csf interpretation of tuberculosis
high pressure
sometimes cloudy
50-5000 lymphocytes x10^6/L
low glucose
high protein
myobacteria found on zn stain and culture (slow growing)
what is the first line management for meningitis
antibiotics
ideally give after lp and blood culture, but often started early to prevent delay
delay to initiation of antibiotics leads to worse outcomes
what are further management measures for meningitis
supportive treatment - manage shock (fluid for hypotension), may require intensive care for organ support/ventilation
management of complications - surgical input for abscess or empyema, anti-seizure medications
