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IDMM > CNS infections (4) > Flashcards

CNS infections (4) Flashcards

1
Q

what is meningitis

A

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

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2
Q

viral causes of meningitis (KNOW)

A
  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
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3
Q

bacterial causes of meningitis (KNOW)

A

S. pneumonia
N. meningitidis
H. influenza

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4
Q

fungal causes of meningitis (KNOW)

A

cryptococcus

coccidioimycosis

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5
Q

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

A

Lyme disease
neurosyphilis
TB

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6
Q

most common etiology of meningitis in neonates

A

GBS, E. coli, Listeria monocytogenes

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

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7
Q

describe the infection pathway of bacterial meningitis

A
  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

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8
Q

what etiologic agents (generally) cause CNS via:

  1. hematogenous spread
  2. contiguous (sinus, ear, face)
  3. direct inoculation (trauma, surgery)
  4. via nerves
A
  1. most agents
  2. bacteria
  3. bacteria
  4. HSV, VZV
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9
Q

clinical presentation of meningitis

A

systemic infection = “classic triad”–>
FEVER, HEADACHE, NUCHAL RIGIDITY

  • altered mental status
  • photophobia
  • nausea/vomiting
  • neuro symptoms (seizures, cranial nerve palsies)
  • rash (with meningococcal meningitis)
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10
Q

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

A
  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
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11
Q

why do a CT before an LP when testing for meningitis

A

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

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12
Q

what test is done to diagnose meningitis

A

LP to obtain CSF and then culture/testing

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13
Q 
what are CSF WBC levels in 
1. bacterial
2. viral
3. fungal/TB 
meningitis
A

normal CSF WBC =

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14
Q 
what are CSF WBC cell types present in 
1. bacterial
2. viral
3. fungal/TB
meningitis
A

normal CSF WBC type = none

bacterial = >80% neutrophils
viral = lymphocytes 
fungal/TB = lymphocytes
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15
Q 
what are the CSF glucose levels in 
1. bacterial
2. viral
3. fungal/TB 
meningitis
A

normal CSF glucose level = 3.3-4.4 mmol/L

bacterial = low
viral = normal 
fungal/TB = normal
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16
Q 
what are the CSF protein levels in 
1. bacterial
2. viral
3. fungal/TB
meningitis
A

normal CSF protein = 400-1200

bacterial = high 
viral = normal or high 
fungal/TB = normal or high
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17
Q

Tx for meningitis

A

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

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18
Q

what is encephalitis

A

infection of brain parenchyma

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19
Q

what distinguishes encephalitis from meningitis clinically

A

encephalitis has absence of normal brain function

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20
Q

viral causes of encephalitis

A

MOST COMMON = VIRAL

  1. HSV–life threatening
  2. VZV–most common
  3. also measles, mumps, rabies, west nile, HIV, polio, CMV
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21
Q

nonviral causes of encephalitis

A

tick borne
bacteria
protozoa

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22
Q

noninfectious causes of encephalitis

A

tumors
vasculitis
drugs

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23
Q

postinfectious causes of encephalitis

A

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

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24
Q

Describe HSV encephalitis pathophysiology

A

acute, necrotizing, asymmetrical, hemorrhagic process

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

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25
Q

symptoms of parenchymal involvement in encephalitis

A

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
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26
Q

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
A
  1. west nile encephalitis
  2. west nile encephalitis
  3. rabies
  4. VZV
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27
Q

how do you diagnose encephalitis

A

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

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28
Q

Tx for encephalitis

A

supportive care and therapy versus infective agent

**IV ACYCLOVIR empirically until HSV is ruled out

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29
Q

risk factors for brain abscess

A
  1. immunosuppression
  2. cardio-pulmonary conditions
  3. head trauma
30
Q

what causes brain abscess in an immunocompetent host

A

POLYMICROBIAL bacterial infection

strep anginosus group
anaerobes
staph aureus
gram - orgs

31
Q

what causes brain absesses in an immunocompromised host

A

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

32
Q

how does a brain abscess develop

A

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
Q

how is brain abscess diagnosed

A

CT scan of head

34
Q

Tx of brain abscess

A

aspiration

empiric Abs–> CEFTRIAXONE + METRONIDAZOLE +/- Vanco

or

MEROPENEM +/- Vanco

glucocorticoids if have significant swelling

35
Q

what is an epidural abscess

A

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

36
Q

what organisms cause epidural abscess

A

STAPH AUREUS = most

gram - bacilli
streptococci
coagulase - staph
anaerobes
M. TB
37
Q

how does epidural abscess present clinically

A

classic triad: fever, back pain, neuro deficits

shooting pain
motor weakness and sensory changes
paralysis

38
Q

Tx for epidural abscess

A

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

surgical decompression and drainage

39
Q

etiology of viral conjunctivitis

A

“pink eye”

adenovirus
enteroviruses

40
Q

etiology of bacterial conjunctivitis

A

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

41
Q

what are key negatives in the clinical presentation of viral conjunctivitis

A

absence of eye pain

visual acuity is normal

42
Q

how does viral conjunctivitis present

A

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
Q

how does bacterial conjunctivitis present

A 
redness in SINGLE eye
purulent discharge
matted eyelids on wakening
conjunctival hyperemia
eyelid swelling
44
Q

Tx of viral conjunctivitis

A

supportive

prevent spread because is highly contagious

45
Q

Tx of bacterial conjunctivitis

A

fluoroquinolone drops

TMP-SMX
ointment

46
Q

what is hyperacute bacterial conjunctivitis

A

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
Q

what is chlamydial conjunctivitis

A 
inclusion infection
follicular response
adults get sex transmitted
neonates from birth canal
requires systemic therapy
48
Q

what is trachoma

A

“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
Q

red flags for optho referral

A
  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
Q

what is keratitis

A

inflammation of the cornea

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

51
Q

bacterial causes of keratitis

A

S. aureus
S. pneumo
GAS
gram -s

**from contacts: pseudomonas aeruginosa

52
Q

viral causes of keratitis

A

HSV1

adenovirus
VZV

53
Q

fungal causes of keratitis

A

fusacarium spp

54
Q

parasitic causes of keratitis

A

acanthamoeba

severe eye pain, photophobia

from using tap water to clean contacts

55
Q

what is a hypopon

A

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

56
Q

how does keratitis present

A

EYE PAIN
DECREASED VISION
(both unlike conjunctivitis)

foreign body sensation
photophobia
conjunctival infection 
tearing and discharge
corneal infiltrate or ulcer (change in transparency)
57
Q

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

A

bacterial cause

58
Q

what does a branching opacity in the cornea indicate in keratitis

A

viral cause

59
Q

how is keratitis diagnosed

A

slit lamp exam

fluorescein dye to reveal corneal defect

60
Q 
Tx for 
1. viral
2. fungal
3. bacterial
4. parasitic
keratitis
A
  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
Q

what is endopthalmitis

A

infection of vitreous humor or aqueous humors

62
Q

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

A

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

63
Q

etiology of endopthalmitis

A 
bacterial = S. aureus, coag - staph, strep, gram -s
fungal = candida
64
Q

clinical presentation of endopthalmitis

A

decreasing vision

eye “ache”

65
Q

Tx for endopthalmitis

A

MEDICAL EMERGENCY

intravitreal Abs–> VANCO + CEFTAZIDIME

66
Q

what causes periorbital cellulitis

A

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

67
Q

clinical presentation of periorbital cellulitis

A 
ocular pain
eyelid swelling
erythema
FULL RANGE of eye movement 
NO double vision
NO increased pain with eye movement 
no proptosis (eye bulging)
68
Q

Tx for periorbital cellulitis

A

clindamycin or amoxicillin +/- TMP-SMX

NO topical

69
Q

etiology of orbital cellulitis

A 
S. aureus
S. pneumo
anaerobes
H. influenzae
polymicrobial
70
Q

why is orbital cellulitis taken so seriously

A

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

infection can spread from orbit into cavernous sinus and intracranial structures

71
Q

clinical presentation of orbital cellulitis

A 
ocular pain
eyelid swelling
erythema
PAIN WITH EYE MOVEMENT 
PROPTOSIS
DOUBLE VISION
fever
chemosis
complications = vision loss and brain ascess
72
Q

Tx of orbital cellulitis

A

vanco + piper/tazo

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

IDMM (29 decks)

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