Infections Of The CNS Flashcards
List the possible route of infection for meningitis
Blood-borne
Parameningeal suppuration e.g. otitis media, sinusitis
Direct spread through defect in the duration e.g. trauma
Direct spread through cribriform plate (rare)
CSF stile, immune system can’t cope
List the complications alongside meningitis
death subdural collection cerebral vein thrombosis hydrocephalus 9-15% deafness (Hib) convulsions visual/motor/sensory deficit
Below are the common organisms that cause meningitis, what group are they commonly found in?
Neisseria meningitidis Streptococcus pneumoniae Hib Escherichia coli Listeria monocytogenes
neisseria meningitidis - children/young adults
strep pneumoniae - elderly and children <2 yrs
Hib - children <5yrs
e.coli - neonates
listeria - neonates/immunocompromised
What are the levels of protein
IgG
lymphatics in cerebrospinal fluid?
LOW
and no lymphatics
Describe the inflammatory process in meningitis
Release inflammatory mediators - TNF, IL-1&8, PAF and NO
neutrophils migrate to the CSF, release proteolytic products and toxic O radicals
vascular endothelium is damages, BBB is reduced = alteration of CSF and blood supply dynamics
What symptoms arise in meningitis
where else can these symptoms occur?
global headache
neck and back stiffness
nausea and vomiting
photophobia
infections, SAH, malignancy, NSAIDs
What symptoms are found in infants with meningitis (typical signs aren’t present in <18/12)
flaccid- later opisthotonus (muscle spasms) bulging fontanelle due to increased ICP fever and vomiting strange cry convulsions
List the physical symptoms of meningitis
fever
rash - petechial/purpuric (meningococcal usually)
irritation - photophobia, Kernig’s positive, neck stiffness, Brudzinski’s sign
Why have a lumbar puncture in meningitis?
most rapid diagnostic test
distinguish between bacterial and viral
risk of herniation
How does the CSF change in meningitis for bacterial, tuberculous and viral?
leucocytes neutrophiles lymphocytes protein glucose
increase in leucocytes and lymphocytes and neutrophiles
decrease in glucose
What organisms are common in community acquired meningitis?
51% s.pneumoniae
37%n.meningitidis
4% l.monocytogenes
What complications are associated with meningococcal disease
death necrotic lesions reactive arthritis (young adults) serositis neurological sequelae (rare) abscess formation (rare)
List the risk factors of a poor outcome with meningococcal disease
advanced age presence of otitis media or sinusitis absence of rash tachycardia low GCS positive blood culture thrombocytopenia low CSF fluid - white cell count
Give the general management of meningitis
antibiotics adequate oxygenation prevention of hypoglycaemia and hypotraemia anticonvulsants decrease intracranial hypertension
What makes a good antibiotic for meningitis
bactericidal
sufficient penetration into CSF at non-toxic doses
low levels of endotoxin release when organisms killed?
What are the differences between the BBB and the B-CSF barrier
BBB - no fenestrations in the endothelium, thick basement membrane, has astrocytes
B-CSF - fenestrated, thin basement membrane, has choroid plexus
Penetration of antibiotics into CSF is enhanced by…?
high lipid solubility low molecular weight low degree of ionisation high serum concentration low degree of protein binding meningeal inflammation
There are three groups of CSF penetration:
1 penetrate inflamed and non-inflamed at standard dose
2 penetrate inflamed/high dose
3 penetrate poorly
give an example of each
1 metronidazole, trimethoprim, sulphonamides
2 benzylpenicillin, cephalosporins, rifampicin, vancomycin, amB
3 gentamicin, cephalosporins, erythromycin, tetracycline
What is chloramphenicol used for
reserve agen for allergic patients with meningitis
resistance in Hib and pneumococci
What is cefotaxime/ceftriaxone used for
first line treatment for meningitis in adults and children, NOT for listeria
can be used if someone has a penicillin allergy
What is benzylpenicillin used for
Best for pneumococcal meningitis
high levels can lower threshold for epileptic fits
not for haemophilus influenze
What are the penetration of antibiotics into the brain/blood ratio for
chloramphenicol
cefotaxime/ceftriaxone
benzylpenicillin G
9: 1
1: 10
1: 23
Roughly how to treat meningitis with antibiotics
meningococcus 7
pneumococcus 14
haemophilus 7
listeria 21
if organism is not isolated this should be IV 7-14 days
what is the link between meningitis and steroids
give steroids prior to antibiotics for beneficial effect
