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Flashcards in CNS infections (4) Deck (72):
1

what is meningitis

inflammation of the meninges (the membranes covering the brain and spinal cord) i.e dura, arachnoid, subarachnoid space

2

viral causes of meningitis (KNOW)

1. enteroviruses--> coxsackievirus and echoviruses (85-95% of cases of viral meningitis)--fecal-oral spread
2. HSV-2 in neonates
3. HIV
4. West Nile

3

bacterial causes of meningitis (KNOW)

S. pneumonia
N. meningitidis
H. influenza

4

fungal causes of meningitis (KNOW)

cryptococcus
coccidioimycosis

5

other causes of meningitis (not viral, bacterial, fungal) (KNOW)

Lyme disease
neurosyphilis
TB

6

most common etiology of meningitis in neonates

GBS, E. coli, Listeria monocytogenes

*rest of age groups its S. pneumo, N. meningitidis, H. influenzae (and maybe L. monocytogenes)

7

describe the infection pathway of bacterial meningitis

1. nasoparyngeal colonization-->local invasion--> bacteremia--> endothelial injury
2. endothelial injury causes both increased permeability in the BBB as well as meningeal invasion
3. meningeal invasion causes subarachnoid space inflammation which in turn causes even more BBB permeability
4. subarachnoid space inflammation also causes:
(a) cerebral vasculitis--> cerebral infarction--> decreased cerebral blood flow --> death
(b)increased CSF outflow resistance--> hydrocephalus--> interstitial edema--> increased intracranial pressure--> reduced cerebral blood flow--> death
(c)cytotoxic edema--> increased intracranial pressure--> decreased cerebral blood flow--> death
5. the increased BBB permeability causes vasogenic edema which causes increased intracranial pressure--> decreased cerebral blood flow--> death

*overall, meningeal invasion can lead to subarachnoid space inflammation which can lead to increased intracranial pressure through various edemas which leads to decreased cerebral blood flow and thus death

8

what etiologic agents (generally) cause CNS via:
1. hematogenous spread
2. contiguous (sinus, ear, face)
3. direct inoculation (trauma, surgery)
4. via nerves

1. most agents
2. bacteria
3. bacteria
4. HSV, VZV

9

clinical presentation of meningitis

systemic infection = "classic triad"-->
FEVER, HEADACHE, NUCHAL RIGIDITY

-altered mental status
-photophobia
-nausea/vomiting
-neuro symptoms (seizures, cranial nerve palsies)
-rash (with meningococcal meningitis)

10

what are some signs of meningeal infection? (particularly useful in children)

1. neck stiffness
2. KERNIG SIGN--> with patient lying on back and knee at 90 degrees, knee extensions elicit resistance or pain in lower back
3. BRUDZINSKI SIGN--> passive neck flexion in supine patient results in flexion of knees and hips
4. cranial nerve palsies
5. papilledema--> blurring of edges of optic nerve disc due to increased intracranial pressure

11

why do a CT before an LP when testing for meningitis

to prevent unrecognized increased intracranial pressure leading to cerebral herniation and death when the LP is performed

12

what test is done to diagnose meningitis

LP to obtain CSF and then culture/testing

13

what are CSF WBC levels in
1. bacterial
2. viral
3. fungal/TB
meningitis

normal CSF WBC =

14

what are CSF WBC cell types present in
1. bacterial
2. viral
3. fungal/TB
meningitis

normal CSF WBC type = none

bacterial = >80% neutrophils
viral = lymphocytes
fungal/TB = lymphocytes

15

what are the CSF glucose levels in
1. bacterial
2. viral
3. fungal/TB
meningitis

normal CSF glucose level = 3.3-4.4 mmol/L

bacterial = low
viral = normal
fungal/TB = normal

16

what are the CSF protein levels in
1. bacterial
2. viral
3. fungal/TB
meningitis

normal CSF protein = 400-1200

bacterial = high
viral = normal or high
fungal/TB = normal or high

17

Tx for meningitis

MEDICAL EMERGENCY

start Tx ASAP

empiric therapy = CEFTRIAXONE + VANCOMYCIN (for penicillin resistant S. pneumo)
+/- amoxicillin (elderly, immunesupp, pregnant)
+/- dexamethasone

mortality highest with S. pneumo meningitis

18

what is encephalitis

infection of brain parenchyma

19

what distinguishes encephalitis from meningitis clinically

encephalitis has absence of normal brain function

20

viral causes of encephalitis

MOST COMMON = VIRAL

1. HSV--life threatening
2. VZV--most common
3. also measles, mumps, rabies, west nile, HIV, polio, CMV

21

nonviral causes of encephalitis

tick borne
bacteria
protozoa

22

noninfectious causes of encephalitis

tumors
vasculitis
drugs

23

postinfectious causes of encephalitis

acute disseminated encephalomyelitis (ADEM)--thought to be immune mediated

24

Describe HSV encephalitis pathophysiology

acute, necrotizing, asymmetrical, hemorrhagic process

pathway to CNS if through trigeminal/olfactory nerves and hematogenous spread

25

symptoms of parenchymal involvement in encephalitis

seizures
mental status changes
focal neuro signs

HSV--> acute onset
-focal neuro signs including hemiparesis, ataxia, aphasia, seizures
-usually rapidly progressive
-common sequela = memory and behavior disturbances

26

a patient presents with encephalitis + one of the following... for each, what does this presentation suggest as an etiologic agent?
1. flaccid paralysis
2. tremors (eye, lips, extremities)
3. hydrophobia, aerophobia, pharyngeal spasms, hyperactivity
4. vesicular rash

1. west nile encephalitis
2. west nile encephalitis
3. rabies
4. VZV

27

how do you diagnose encephalitis

LP with CSF profile
serology for arbovirus (west nile)
brain biopsy as last resort

**must rule out HSV due to high mortality--> CT/MRI for necrosis, PCR of CSF, biopsy

28

Tx for encephalitis

supportive care and therapy versus infective agent

**IV ACYCLOVIR empirically until HSV is ruled out

29

risk factors for brain abscess

1. immunosuppression
2. cardio-pulmonary conditions
3. head trauma

30

what causes brain abscess in an immunocompetent host

POLYMICROBIAL bacterial infection

strep anginosus group
anaerobes
staph aureus
gram - orgs

31

what causes brain absesses in an immunocompromised host

parasites (toxoplasma gondii)
fungal (crytococcus neoformans)
mycobacteria (M. TB)
as well as those that affect immunocompetent hosts

32

how does a brain abscess develop

begins as localized cerebritis (1-2 weeks) and evolves into collection of pus with well vascularized capsule (3-4 weeks)

leads to compression of brain parenchyma and thus increased intracranial pressure and this interferes with CSF flow

33

how is brain abscess diagnosed

CT scan of head

34

Tx of brain abscess

aspiration

empiric Abs--> CEFTRIAXONE + METRONIDAZOLE +/- Vanco

or

MEROPENEM +/- Vanco

glucocorticoids if have significant swelling

35

what is an epidural abscess

collection of suppurative fluid between the dura and the bones of the skull or the spinal cord

36

what organisms cause epidural abscess

STAPH AUREUS = most

gram - bacilli
streptococci
coagulase - staph
anaerobes
M. TB

37

how does epidural abscess present clinically

classic triad: fever, back pain, neuro deficits

shooting pain
motor weakness and sensory changes
paralysis

38

Tx for epidural abscess

Ab therapy = culture guided but empiric is CEFTRIAXONE + METRONIDAZOLE + VANCO

surgical decompression and drainage

39

etiology of viral conjunctivitis

"pink eye"

adenovirus
enteroviruses

40

etiology of bacterial conjunctivitis

S. aureus
S. pneumo
H. influenzae
S. pyogenes (GAS)

41

what are key negatives in the clinical presentation of viral conjunctivitis

absence of eye pain
visual acuity is normal

42

how does viral conjunctivitis present

watery discharge--morning crust
irritation
hyperemia
burning/itching eyes

adenoviral--> pharyngeoconjunctival fever with pre-auricular adenopathy //or// epidemic keratoconjunctivitis--> inflammation of conjunctiva and corneo; subconjunctival hemorrhage; membrane erythema

43

how does bacterial conjunctivitis present

redness in SINGLE eye
purulent discharge
matted eyelids on wakening
conjunctival hyperemia
eyelid swelling

44

Tx of viral conjunctivitis

supportive

prevent spread because is highly contagious

45

Tx of bacterial conjunctivitis

fluoroquinolone drops

TMP-SMX
ointment

46

what is hyperacute bacterial conjunctivitis

due to N. GONORRHEA

profuse discharge with in 12-24 hours

chemosis, hyperemeia, eyelid edema

SEVERE AND VISION THREATENING --> need immediate optho referral (keratitis and perforation can occur)

47

what is chlamydial conjunctivitis

inclusion infection
follicular response
adults get sex transmitted
neonates from birth canal
requires systemic therapy

48

what is trachoma

"rough eye"

due to repeated infection with C. trachomatis--> eyelid eventually flips, eyelashes scratch eye causing blindness

most common cause of preventable blindness worldwide

49

red flags for optho referral

1. decreased vision
2. photophobia
3. severe foreign body sensation
4. corneal opacity
5. severe headache and nausea
6. history of clinical exam, previously tried therapies

50

what is keratitis

inflammation of the cornea

*cornea is nourished by tears and aqueous humor, not blood vessels

51

bacterial causes of keratitis

S. aureus
S. pneumo
GAS
gram -s

**from contacts: pseudomonas aeruginosa

52

viral causes of keratitis

HSV1

adenovirus
VZV

53

fungal causes of keratitis

fusacarium spp

54

parasitic causes of keratitis

acanthamoeba

severe eye pain, photophobia

from using tap water to clean contacts

55

what is a hypopon

pus layering at bottom of chamber, i.e in keratitis due to inflammatory response

56

how does keratitis present

EYE PAIN
DECREASED VISION
(both unlike conjunctivitis)

foreign body sensation
photophobia
conjunctival infection
tearing and discharge
corneal infiltrate or ulcer (change in transparency)

57

what does a round white spot in the cornea indicate in keratitis

bacterial cause

58

what does a branching opacity in the cornea indicate in keratitis

viral cause

59

how is keratitis diagnosed

slit lamp exam
fluorescein dye to reveal corneal defect

60

Tx for
1. viral
2. fungal
3. bacterial
4. parasitic
keratitis

1. acyclovir ointment
2. topical antifungals like amphotericin
3. fluoroquinolone drops (no contacts)
aminoglycoside (i.e gentamycin) + pipercillin drops for people wearing contacts to cover pseudomonas
4. propamidine + something else

61

what is endopthalmitis

infection of vitreous humor or aqueous humors

62

why does even a small inoculum in the aqueous humor cause infection

because the aqueous humor has a low bacterial burden and the immune system is unable to clear even a small inoculum

63

etiology of endopthalmitis

bacterial = S. aureus, coag - staph, strep, gram -s
fungal = candida

64

clinical presentation of endopthalmitis

decreasing vision
eye "ache"

65

Tx for endopthalmitis

MEDICAL EMERGENCY

intravitreal Abs--> VANCO + CEFTAZIDIME

66

what causes periorbital cellulitis

S. aureus
S. pneumo and other strep
anaerobes
H. influenzae

67

clinical presentation of periorbital cellulitis

ocular pain
eyelid swelling
erythema
FULL RANGE of eye movement
NO double vision
NO increased pain with eye movement
no proptosis (eye bulging)

68

Tx for periorbital cellulitis

clindamycin or amoxicillin +/- TMP-SMX

NO topical

69

etiology of orbital cellulitis

S. aureus
S. pneumo
anaerobes
H. influenzae
polymicrobial

70

why is orbital cellulitis taken so seriously

it can lead to loss of vision and even be life threatening

infection can spread from orbit into cavernous sinus and intracranial structures

71

clinical presentation of orbital cellulitis

ocular pain
eyelid swelling
erythema
PAIN WITH EYE MOVEMENT
PROPTOSIS
DOUBLE VISION
fever
chemosis
complications = vision loss and brain ascess

72

Tx of orbital cellulitis

vanco + piper/tazo

surgery is indicated if poor response to antibiotics, worsening vision, evidence of abscess