Meningitis Flashcards
what is meningitis
inflammation of meninges
diagnosis of meningitis
history, phys exam, lab tests
lumbar puncture = inc pressure in subarachnoid space, cloudy, purulent CSF, inc neuts + proteins, dec protein, bac on smears + cultured
lumbar puncture could result in brain herniation, CT to make sure not at risk
pathophysiology of meningitis. starting with bacterial replication
bacteria replicate + lysis in CS -> release endotoxins.cell wall fragments -> infam mediators + neuts recruits -> inc BBB -> albumin enters -> cerebral oedema -> abnormal fluid in brain tissue => life threatening
pathophysiology of meningitis. starting with oathogens in subarachnoid space
pathogens enter -> inflam, cloudy purulent fibrinous exudate
vascular congestion -> thrombophlebitis of bridging veins in dural sinuses, blockage/collapse arterioles -> infarction tissue
meninges thicken + adhesions form -> impinge cranial nerves -> cranial nerve palsies -> impair outlow CS -> hydrocephalus
decribe cereal oedema
excess fluid brain
vasogenic oedema
- disrupted BBB
- albumin into tissue
- water flows doen osmotic gradient
- inc fluid, inc brain V
treatment = osmotic agents = pull excess water out brain lower ICP (mannitol, hypertonic saline), or decompressive surgery = remove skull cap, incise dura allows brain room to lower ICP
compensatory mechanisms for ICP
-venous vasoconstriction = reduce venous V to dec V in skull
- shunt off CSF = dec CS V = dec total V skull
- atrial vasconstriction = constriction artieral circ -> dec arterial blood V -> not enough blood -> deprives O2 + nutrients
- arterial vasodilation = desperate for o2 -> inc blood V -> furthe rinc ICp
clinical signs elevated ICP
rapid deterioration = dec conscious, bradycardia, hypervent, ilated/sluggish pupils )CN III copression)
bypoxia + lactic acidosis = further vasodilation => inc V
ICp continues to inc = tissue has hypercapnia -> inc CO2 = vasodilation -> further inc ICP
when ICP = systolic aertieral pressure => bloof flow to brain ceases => death
brain herniation + loss autoregulation when CPP < 40 mmHg
persistently elevates ICP = compromise brain function, compress adjacent structures, compress bv, -> ischaemia, worsen brain injury
describe compression of brain structure
subfalcine herniation = cingualte gyrus pushes under falx cerebi
transtentorial herniation = cerebral hemisphere push down towards brain stem => fixed/sluggish dilated pupils
tonsillar herniation = cerebellar tonsils down towards sc (oramen magnum) = compress vital centres resp + cardiac, intermittent resp = death
hydropcephalus as meningitis complication
enlarge ventricles = abnormal inc V VSF = imbalance CSF production and reabsorption
adhesions formes + fibrinous ecudate impede outlofw CSF
non-communicating (obstructive) hydrocephalus
inc ICP
treatent = CSF shunt
signs meningitis
fever chills
headaches, nausea, comiting,
back + abdominal + extemity pain = irritation of meningnes, stim innervating nerve to mediate pain
photophobia
stiff neck
drowsiness,difficulty waking up
confusion, irritability
seizures
cranial nerve palsies
focal cerebral signs
meningeal presentations - stretching
resistance to painful stretching of inflames meninges from lumbar to head
muchal rigidity = passive/active flexion of neck = cant touch chin to chest
kernig sign = resistance to extension knee when lying with hip flexed at right angle
brudzinkski sign = elicited when flexion neck induces flexion hip + knee
meningeal presentations = meningococcus meningitis
petechial rash with palpable purpura
variation size = pinhead (petechiae), large regions (eccymoses - bruise like), skin gangrene
evere skin/tissue injury caused by diffuse intravascular coag
not everyone gets rash
treatment bacterial meningitis
delay = bad
urgent antibiotics
age/reecnt clinical hsitory guides antibiotics selection
broad spectrum coverage antibiotics (3rd gen cephalosporin deals with gram pos & neg)
adjustment antibiotic regime driven by CSF bacterial culture results
antibiotics => pathogen lysis => inflam mediators, can worsen BBB
adjunctive corticosteroids
close contacts given clearance antibiotics to reduce spread
causes of viral meningitis
less severe + swift recovery
common = coxsackievirus, poliovirus, echovirus
others = epstein-barr virus, mumps, herpes simplex virus, west nile virus
clinical presentiation of viral meningitis
fever, severe headache esp behind eyes, photophobia, nausea + vom
depending on causative agent = sore throat, chest pain, swollen parotid gland, skin rash
