Intro to CNS Infection

Question 2

how does the blood brain barrier achieve its function?

Answer 2

interendothelial tight junctions, enzymatic barrier, efflux pumps, low levels of endo- and transcytosis

Question 3

what cells are involved in the BBB?

Answer 3

capillary endothelial cells surrounded by pericytes, basal lamina, and astrocytes

Question 4

what does it mean that the CNS is “immune privileged”?

Answer 4

there is restricted immunological defense: no lymphatics in brain, limited complement in the CSF, low MHC expression (restrict potential inflammatory reactions)

Question 5

what CNS cells do express MHC?

Answer 5

microglia and perivascular macrophages

Question 6

what is the role of astrocytes in the CNS?

Answer 6

express TLR4, produce TGFb – inflammatory activity and suppression

Question 7

what is the role of microglia in the CNS?

Answer 7

highly phagocytic macrophages of CNS tissue, poor APCs, express TLR4, activated lead to inflammatory mediators (no DCs in brain, but microglia can morph to look like them)

Question 8

what is the role of mast cells in the CNS?

Answer 8

produce TNF in the meninges, facilitate T cell entry during inflammation by increasing permeability of endothelial cells

Question 9

name 3 potential health side effects of mast cell activity in the CNS

Answer 9

inflammation, autism, seizures

Question 10

when can T and B cells enter the CNS?

Answer 10

only activated T cells stimulated in peripheral lymph nodes & activated B cells in response to inflammation-induced permeability of BBB

Question 11

how do immune arcs in the CNS compare to the periphery?

Answer 11

there is a severely dampened afferent cellular arm, same afferent soluble, slightly decreased efferent cellular

Question 12

what is encephalitis?

Answer 12

acute inflammation of brain parenchyma (could also have a brain abscess)

Question 13

what is meningitis?

Answer 13

acute or chronic inflammation of the meninges

Question 14

top microbial causes of acute meningitis

Answer 14

encapsulated bacteria (strep pneumo, n. meningitidis); arboviruses; enteroviruses; HSV2

Question 15

major microbial causes of chronic meningitis

Answer 15

myco. Tuberculosis, cryptococcus neoformans (pathogenic encapsulated yeast), other fungi

Question 16

microbial causes of acute brain abscess

Answer 16

staph, mixed flora, GAS

Question 17

microbial causes of chronic brain abscess

Answer 17

myco TB, cryptococcus neoformans, taenia solium (cysticercosis), toxoplasma gondii

Question 18

what are the three major entry routes for microbes in the CNS

Answer 18

blood via choroid plexus (more permeable, achilles heel), retrograde passage on neurons (or through olfactory nerve), direct inoculation from trauma or defects

Question 19

name 3 ways that microbes can get into the blood circulation

Answer 19

colonization and penetration of mucosal epithelium, bite of an infected animal, transplacental

Question 20

name a bacteria and a class of viruses that can directly infect endothelial cells in the brain

Answer 20

Rickettsia (RMSF) & arboviruses

Question 21

name 4 important epidemiological factors that influence source of CNS infection

Answer 21

age, immunocompetence, geographic location, time of year

Question 22

what microbes should be on the differential for bacterial meningitis in neonates?

Answer 22

Group B strep, E. coli, Listeria

Question 23

what microbes should be on the differential for bacterial meningitis in healthy adults?

Answer 23

strep pneumo, neisseria meningitidis

Question 24

what microbes should be on the differential for bacterial meningitis in an immunosuppressed patient?

Answer 24

listeria or gram negative rods

Question 25

name three major components of CNS damage

Answer 25

1. death of CNS cells from infecting microbe, 2. tissue destruction from host immune response, 3. cerebral edema from inflammation

Question 26

major signs of frontal lobe abscess

Answer 26

sinusitis, HA, memory defects, attention loss, decreased intellect

Question 27

major signs of temporal lobe encephalitis

Answer 27

personality changes, visual field defects, hemiparesis, focal seizures

Question 28

major signs of basilar meningitis

Answer 28

suboccipital HA, neck stiffness, double vision, cranial nerve palsies

Question 29

physical exam findings of CNS infections

Answer 29

neck and back rigidity, HA, vomiting, photophobia, Kernig’s sign, Brudzinski’s sign, mental status changes, decreased blood pressure

Question 30

how to diagnose a CNS infection

Answer 30

1. start on antibiotics just in case, 2. obtain blood cultures from 2 locations, 3. get CT right away, 4. get LP if no abscess or altered consciousness

Question 31

describe the CSF findings in a person without any CNS infection

Answer 31

minimal WBCs, mononuclear predominance, CSF:blood glucose >0.5, protein 20-50

Question 32

describe the CSF findings in a person with viral meningitis

Answer 32

10-1000 WBCs (varied), mononuclear predominance, normal glucose, protein 50-100 (high)

Question 33

describe the CSF findings in a person with bacterial meningitis

Answer 33

1000-5000 WBCs (very high), neutrophil/PMN predominance, CSF:blood glucose <0.5 (low), protein 100+ (very high)

Question 34

describe the CSF findings in a person with TB meningitis

Answer 34

100-500 WBC (high), lymphocyte predominance, low glucose, very high protein

Question 35

describe the CSF findings in a person with cryptococcal meningitis

Answer 35

100-500 WBC (high), lymphocyte predominance, low glucose, protein 50-100 (high, but not as high as TB)