Intro to CNS Infections Flashcards Preview

Neuro Block 2 > Intro to CNS Infections > Flashcards

Flashcards in Intro to CNS Infections Deck (31):
1


What are the three big symptoms of CNS infections?


fever, headache, altered mental state

2

What are the three main infectious causes of fever, headache and altered mental state?


meningitis

encephalitis

abscess

3


What is encephalopathy?


Diffuse cerebral dysfunction WITHOUT inflammation -- probably due to toxin or metabolic dysfunction

4

Why are infections of the CNS uncommon?


 - the scalp and skull protect it from external entry

- three meninges surround the brain and spinal cord

- tight junctions of BBB prevent organisms from entering the CNS

5

In the CNS, is the immune response more innate or adaptive?


innate

6

What are 4 characteristics of microbial invasion to the brain?


1. hematogenous dissemination

2. contiguous spread from sinusitis, otitis media, or mastoiditis

3. trauma or congenital lesions make it easier

4. retrograde axonal transport (especially the viruses)

7

How are CNS infections categorized?


where in the brian they occur

8

What are the 4 main types of CNS infections and where do they occur?


meningitis = subarachnoid space

encephalitis = diffuse parenchyma

abscess = focal parenchyma

myelitis = spinal cord

9

What are the typical steps in diagnosis of a CNS infection?


1. History and physical

2. blood culture and EMPIRIC TREATMENT

3. Neuroimaging

4. Lumbar puncture/biopsy

5. Identificaiton of organism

6. antibiotic susceptibitility testing

7. switch to definitive treatment/supportive therapy

10

If neuroimaging doesn't get you much, why is it still good to obtain if you're concerned about CNS infection?


It tells you if there's too much cerebral edema to safely do a lumbar puncture

11

What is the most common cuase of viral meningitis/encephalitis and when in the year does it occur most often?


enterovirus - usually in late summer to fall

12

What are the perinatal CNS infections to be concerned about? Remember they can have mild maternal morbidity, but serious fetal consequences.


group B strep

E. coli

Listeria

TORCH: Toxoplasmosis, Other (symphilis, varicella zoster, parvovirus), Rubella, Cytomegalovirus and Herpes Infections (HSV-2)

13

If you are worried about bacterial meningitis, how should you start?


1. take a blood culture first

2. treat with empiric antibiotic - BACTERICIDAL at 10-fold greater than minimum inhibitory concentration

14

WHat characteristics do you want in a drug for CNS infections?


bactericidal, small, lipophilic, low affinity for plasma binding proteins, not a ligand for efflux pumps at the BBB

15

What groups of patients have increased penetration of drugs thorugh the BBB?


newborns and individuals with CNS inflammation

16

What are the three main classes ot antibiotics we should be worried about in terms of CNS toxicities?


Aminoglycosides - ototoxicity thorugh activation of the NMDA receptors

Beta-lactams - inhibit GABAa release so you lose inhibition and become more prone to seizures

Macrolides - ototoxicity thoruhg damage to the cochlea

17

In terms of beta lactams, what patient factor would place them at higher risk for seizures?


decreased renal function - less excretion, buildup of drug, more likely to seize

18

When should you obtain neuroimaging?


trauma

immunocompromised

focal neurologic findings

decreased conciousness

19

If focal mass lesion is identified on neuroimaging, why shouldn't you do an LP?


There will be high intracranial pressure, so risk of brain herniation is too much

20

How can you tell with a WBC whether a meningitis is likely bacterial vs viral?


bacterial = more PMNs

viral = more lymphocytes

21

Which is more common in meningitis - viral or bacterial? Which is more serious?


viral more common

bacterial more serious

22

What additional symptoms will likely occur in encephalitis that don't occur in meningitis?


motor and sensory deficits with potential progression to seizures, speech disturbances, lethargy and coma

23

What percentage of encephalitis cases are of unknown etiology?


33-66%

24

What do you empirically use to treat encephalitis?


acyclovir - until HSV ruled out

25

What are the main viral causes of encephalitis/ Nonviral?


viral - enterovirus, arbovirus, HSV, Rabies

Nonrival - ricckettsia, mycoplasma, acute disseminated encephalomyelitis

26

What will predispose someone to brain abscess formation?


pre-existing ischemia: necrosis begins as cerebritis and then becomes encapsulated

27

Brain abscesses are often associated with mixtures of bacteria, including....


streptococci (most common)

pseudomonas

haemophilus

staphylococcus

bacteroides

28

What determines localization of a brain abscess usually?


where the infeciton started

otitis media goes to the temporal lboes and cerebellum

dental and isnus to the frontal love

hematogenous to multiple sites usually around the middle cerebral artery

29

How do you diagnose a brain abscess?


CT or MRI plus needle aspiration

blood cultures will usually be positive

LP is not beneficial

30

What is the typical treatment for a brain abscess?


ceftriazone and metronidazole

add vanco for staph

may need surgey for pseudomonas

31