CNS Flashcards
(57 cards)
What is the CNS made up of
brain, spinal cord & cranial nerves (but not peripheral nerves).
-protected by skull, vertebrae & layers of meninges.
What is CSF
where is it found
function
-found in subarachnoid space & ventricles.
-Produced by fluid filtered out of blood by brain capillaries called choroid plexus
-circulates around the spine , around the brain and returns to blood
Protect brain/spinal cord.
Regulates pressure.
Supplies nutrients & removes wastes.
Provides some immune cells
CHARACTERISTICS OF CSF
-Clear colorless, sterile fluid.
-has normal amount of WBC
-newborns have higher protein, glucose & WBC (monocytes & neutrophils).
Infection of CSF associated with increased WBC count & change in amount of protein & glucose
BLOOD BRAIN BARRIER (BBB)
Semi-permeable membrane -separates brain tissue from blood.
Protects brain from toxins, & pathogens while letting nutrients in.
If microorganisms get past = encephalitis
BLOOD CSF BARRIER (BCB)
Functional barrier found in choroid plexus of brain ventricles.
Separates blood from CSF & CSF from brain.
Also protects brain from toxins, & pathogens while letting nutrients in.
If microorganisms get past = meningitis or encephalitis
MENINGITIS
Inflammation/infection of CSF & meninges due to virus or bacteria getting past the blood-csf barrier
-serious and can be fatal
-can cause death quickly
-can cause brain damage, hearing loss and learning disabilities
-medical emergency
PATHOGENISIS OF BACTERIAL MENINGITIS
types of spread
Hematogenous spread: Organism enters bloodstream & from blood spreads to CSF & meninges
Contiguous spread:
Organism causing infection in sinus or OM passes through mucosa & gets directly into CSF.
Direct spread via cranial trauma or surgery
Once in CSF, replicate, & cause massive inflammatory reaction – increased fluid in brain& <O2.
Symptoms: Fever, headache/neck pain, altered mental status, death
chart
OTHER BACTERIAL CAUSES OF MENINGITIS
Anaerobic bacteria
Rarely cause meningitis.
When they do, is usually because person had/has brain abscess & organism spreads to CSF
LISTERIA MENINGITIS IN FETUS OR NEWBORN
-if occurs in pregnancy – organism ingested in contaminated food (dairy, lunchmeat, poorly washed raw veg).
-Invades cells & survives intracellularly –moves from cell-cell using actin filaments.
-Enters mom’s blood & cross placental barrier.
Mild flu like illness & diarrhea in mom but can cause premature labor & septic/spontaneous abortion or stillbirth.
-listeria can survive at cold temps
-have actin filments to be able to enter cells and can penetrate intestinal lymph nodes allowing them to spread
if baby has listeria
newborn under or over 7 days
Early onset Listeria in Newborn <7 days:
From intra uterine infection or during birth, causes sepsis & more rarely meningitis - high mortality rate (50%)
Late onset Listeria in Newborn >7 days:
Infection from mom after birth or from environmental source-manifest more as meningitis – has < fatality rate
GBS MENINGITIS IN FETUS OR NEWBORN
-colonize adult intestine & genital tract in women
-can cause endocarditis
-If pregnant can cause serious infection to baby.
-Can infect amniotic fluid & baby - premature rupture of membranes & still birth.
-Screening of GBS on all pregnant women - vaginal /rectal swab at 35-37 wks. gestation.
early vs late onset of GBS
Early onset GBS in Newborn (prenatal & <7 days old)
Baby aspirates amniotic fluid with GBS during birth. Causes pneumoniae or sepsis & sometimes meningitis- > mortality
Late onset GBS in Newborn (at least 7 days old)
Baby infected by mom or from other source after birth.
Causes mostly meningitis, sometimes septicemia or pneumonia-mortality rate is lower than early onset.
GBS
GRAM
CAT
BE
MOT
Col morph: grey, sm/med BH
Gram: GPC in pairs & chains
Catalase: neg
Bile esculin: neg - BIG DIFFERENCE
Motility at 250C: neg
Hippurate hydrolysis: pos
Camp: pos (arrowhead)
PDX: groups with B
Listeria
GRAM
CAT
BE
MOT
Col morph: grey, sm/med BH
Gram: small GPB
Catalase: pos - BIG DIFFERENCE
Bile esculin: pos
Motility at 250C: pos (umbrella)
Hippurate hydrolysis: pos
Camp: pos (rectangle)
PDX: may cross react with group B antisera
VACCINES TO PREVENT MENINGITS
-. influenzae type B conjugate vaccine
a
strep pneua
neiseeira meninigtis
CSF SHUNTS
-Shunts placed in patients with hydrocephalus (excess CSF) drain fluid to relieve pressure
-size of ventricles are increased and puts pressure on the brain
-one goes into CSF and other in the abdomen
BACTERIAL CSF SHUNT INFECTIONS
Early Shunt Infections:
Occur in 4wks of shunt insertion.
Mostly due to normal skin flora like CONs & S. aureus
Happens when proximal end of shunt touches skin. surgical implation . S epi, S aurus, cutibac, corynebac
Late Shunt Infections:
Occur later, > 4wks after shunt insertion.
Usually due to intestinal flora like Enterococcus & GNB.
Happens when fluid from shunt causes perforation or peritonitis.
Strep, entrococcus GNB
ENCEPHALITIS
Inflammation/infection of brain
-small children or elderly
-Caused by invasion of organism (most often due to virus but can also be bacteria, fungus or parasite).
Non-infectious encephalitis due to autoimmune response from tumor or triggered by infection
Brain swelling, headache, stiff neck, sensitivity to light, mental confusion, seizures & death.
medical emergency.
SPECIMEN COLLECTION
-of CSF & blood cultures (blood draw into special BC vials).
-CSF obtained by inserting sterile hollow needle into subarachnoid space of lower lumbar-
-If patient has brain abscess tissue biopsy or aspirates taken because CSF may be normal – also placed in sterile empty container
All CNS specimens are sterile & STAT
All specimens must be transported to the lab as soon as possible – must be plated to media within 1 hour
If CSF delay <24hrs- keep at RT – not refrigerated affects integrity
BRAIN ABSCESS
Pus-filled pocket of infected material in brain
-direct contiguous spread of a cranial infection (skull osteomyelitis, sinus, ear infection).
-hematogenous spread (bacterial endocarditis, IV drug abuse, pneumonia).
-penetrating head wound & neurosurgery.
Is often a polymicrobial infection that includes anaerobes.
-can stop blood from flowing to the brain
INSUFFICIENT QUANTITY OF CSF RECEIVED
only one tube collected, it MUST go to microbiology lab first to ensure sterility of culture
consult with physician to determine testing priorities.
DONT REJECT
CSF SPECIMEN tubes for what
Microbiology gets tube that is least likely to have contamination (tube 2 or 3) for culture & AST -(if possible, never tube 1 in case there wasnt aseptic technique)
Tube 1 sent to Chemistry for glucose & protein testing. least affected by traumatic tap
Tube 3 or 4 sent to Hematology for cell counts (< cell debris)
chem 1, micro 2 , hem 3
consult with physician to determine testing priorities.
-Clear/colorless: normal CSF
-Cloudiness: indicates bacterial or fungal meningitis, a high WBC count, presence of protein or lysed RBC.
-Color, xanthochromia (yellow discoloration): indicates presence of bilirubin & sometimes only sign of acute subarachnoid hemorrhage. check in 30 mins
-Bloody & Cloudy: subarachnoid bleed or traumatic tap
