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
2
Q
viral causes of meningitis (KNOW)
A
- enteroviruses–> coxsackievirus and echoviruses (85-95% of cases of viral meningitis)–fecal-oral spread
- HSV-2 in neonates
- HIV
- West Nile
3
Q
bacterial causes of meningitis (KNOW)
A
S. pneumonia
N. meningitidis
H. influenza
4
Q
fungal causes of meningitis (KNOW)
A
cryptococcus
coccidioimycosis
5
Q
other causes of meningitis (not viral, bacterial, fungal) (KNOW)
A
Lyme disease
neurosyphilis
TB
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)
7
Q
describe the infection pathway of bacterial meningitis
A
- nasoparyngeal colonization–>local invasion–> bacteremia–> endothelial injury
- endothelial injury causes both increased permeability in the BBB as well as meningeal invasion
- meningeal invasion causes subarachnoid space inflammation which in turn causes even more BBB permeability
- 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 - 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
Q
what etiologic agents (generally) cause CNS via:
- hematogenous spread
- contiguous (sinus, ear, face)
- direct inoculation (trauma, surgery)
- via nerves
A
- most agents
- bacteria
- bacteria
- HSV, VZV
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)
10
Q
what are some signs of meningeal infection? (particularly useful in children)
A
- neck stiffness
- KERNIG SIGN–> with patient lying on back and knee at 90 degrees, knee extensions elicit resistance or pain in lower back
- BRUDZINSKI SIGN–> passive neck flexion in supine patient results in flexion of knees and hips
- cranial nerve palsies
- papilledema–> blurring of edges of optic nerve disc due to increased intracranial pressure
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
12
Q
what test is done to diagnose meningitis
A
LP to obtain CSF and then culture/testing
13
Q
what are CSF WBC levels in 1. bacterial 2. viral 3. fungal/TB meningitis
A
normal CSF WBC =
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
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
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
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
18
Q
what is encephalitis
A
infection of brain parenchyma
19
Q
what distinguishes encephalitis from meningitis clinically
A
encephalitis has absence of normal brain function
20
Q
viral causes of encephalitis
A
MOST COMMON = VIRAL
- HSV–life threatening
- VZV–most common
- also measles, mumps, rabies, west nile, HIV, polio, CMV
21
Q
nonviral causes of encephalitis
A
tick borne
bacteria
protozoa
22
Q
noninfectious causes of encephalitis
A
tumors
vasculitis
drugs
23
Q
postinfectious causes of encephalitis
A
acute disseminated encephalomyelitis (ADEM)–thought to be immune mediated
24
Q
Describe HSV encephalitis pathophysiology
A
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
