CNS infections (4) Flashcards
what is meningitis
inflammation of the meninges (the membranes covering the brain and spinal cord) i.e dura, arachnoid, subarachnoid space
viral causes of meningitis (KNOW)
- enteroviruses–> coxsackievirus and echoviruses (85-95% of cases of viral meningitis)–fecal-oral spread
- HSV-2 in neonates
- HIV
- West Nile
bacterial causes of meningitis (KNOW)
S. pneumonia
N. meningitidis
H. influenza
fungal causes of meningitis (KNOW)
cryptococcus
coccidioimycosis
other causes of meningitis (not viral, bacterial, fungal) (KNOW)
Lyme disease
neurosyphilis
TB
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)
describe the infection pathway of bacterial meningitis
- 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
what etiologic agents (generally) cause CNS via:
- hematogenous spread
- contiguous (sinus, ear, face)
- direct inoculation (trauma, surgery)
- via nerves
- most agents
- bacteria
- bacteria
- HSV, VZV
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)
what are some signs of meningeal infection? (particularly useful in children)
- 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
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
what test is done to diagnose meningitis
LP to obtain CSF and then culture/testing
what are CSF WBC levels in 1. bacterial 2. viral 3. fungal/TB meningitis
normal CSF WBC =
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
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
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
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
what is encephalitis
infection of brain parenchyma
what distinguishes encephalitis from meningitis clinically
encephalitis has absence of normal brain function
viral causes of encephalitis
MOST COMMON = VIRAL
- HSV–life threatening
- VZV–most common
- also measles, mumps, rabies, west nile, HIV, polio, CMV
nonviral causes of encephalitis
tick borne
bacteria
protozoa
noninfectious causes of encephalitis
tumors
vasculitis
drugs
postinfectious causes of encephalitis
acute disseminated encephalomyelitis (ADEM)–thought to be immune mediated
Describe HSV encephalitis pathophysiology
acute, necrotizing, asymmetrical, hemorrhagic process
pathway to CNS if through trigeminal/olfactory nerves and hematogenous spread
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
a patient presents with encephalitis + one of the following… for each, what does this presentation suggest as an etiologic agent?
- flaccid paralysis
- tremors (eye, lips, extremities)
- hydrophobia, aerophobia, pharyngeal spasms, hyperactivity
- vesicular rash
- west nile encephalitis
- west nile encephalitis
- rabies
- VZV
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
Tx for encephalitis
supportive care and therapy versus infective agent
**IV ACYCLOVIR empirically until HSV is ruled out
risk factors for brain abscess
- immunosuppression
- cardio-pulmonary conditions
- head trauma
what causes brain abscess in an immunocompetent host
POLYMICROBIAL bacterial infection
strep anginosus group
anaerobes
staph aureus
gram - orgs
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
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
how is brain abscess diagnosed
CT scan of head
Tx of brain abscess
aspiration
empiric Abs–> CEFTRIAXONE + METRONIDAZOLE +/- Vanco
or
MEROPENEM +/- Vanco
glucocorticoids if have significant swelling
what is an epidural abscess
collection of suppurative fluid between the dura and the bones of the skull or the spinal cord
what organisms cause epidural abscess
STAPH AUREUS = most
gram - bacilli streptococci coagulase - staph anaerobes M. TB
how does epidural abscess present clinically
classic triad: fever, back pain, neuro deficits
shooting pain
motor weakness and sensory changes
paralysis
Tx for epidural abscess
Ab therapy = culture guided but empiric is CEFTRIAXONE + METRONIDAZOLE + VANCO
surgical decompression and drainage
etiology of viral conjunctivitis
“pink eye”
adenovirus
enteroviruses
etiology of bacterial conjunctivitis
S. aureus
S. pneumo
H. influenzae
S. pyogenes (GAS)
what are key negatives in the clinical presentation of viral conjunctivitis
absence of eye pain
visual acuity is normal
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
how does bacterial conjunctivitis present
redness in SINGLE eye purulent discharge matted eyelids on wakening conjunctival hyperemia eyelid swelling
Tx of viral conjunctivitis
supportive
prevent spread because is highly contagious
Tx of bacterial conjunctivitis
fluoroquinolone drops
TMP-SMX
ointment
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)
what is chlamydial conjunctivitis
inclusion infection follicular response adults get sex transmitted neonates from birth canal requires systemic therapy
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
red flags for optho referral
- decreased vision
- photophobia
- severe foreign body sensation
- corneal opacity
- severe headache and nausea
- history of clinical exam, previously tried therapies
what is keratitis
inflammation of the cornea
*cornea is nourished by tears and aqueous humor, not blood vessels
bacterial causes of keratitis
S. aureus
S. pneumo
GAS
gram -s
**from contacts: pseudomonas aeruginosa
viral causes of keratitis
HSV1
adenovirus
VZV
fungal causes of keratitis
fusacarium spp
parasitic causes of keratitis
acanthamoeba
severe eye pain, photophobia
from using tap water to clean contacts
what is a hypopon
pus layering at bottom of chamber, i.e in keratitis due to inflammatory response
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)
what does a round white spot in the cornea indicate in keratitis
bacterial cause
what does a branching opacity in the cornea indicate in keratitis
viral cause
how is keratitis diagnosed
slit lamp exam
fluorescein dye to reveal corneal defect
Tx for 1. viral 2. fungal 3. bacterial 4. parasitic keratitis
- acyclovir ointment
- topical antifungals like amphotericin
- fluoroquinolone drops (no contacts)
aminoglycoside (i.e gentamycin) + pipercillin drops for people wearing contacts to cover pseudomonas - propamidine + something else
what is endopthalmitis
infection of vitreous humor or aqueous humors
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
etiology of endopthalmitis
bacterial = S. aureus, coag - staph, strep, gram -s fungal = candida
clinical presentation of endopthalmitis
decreasing vision
eye “ache”
Tx for endopthalmitis
MEDICAL EMERGENCY
intravitreal Abs–> VANCO + CEFTAZIDIME
what causes periorbital cellulitis
S. aureus
S. pneumo and other strep
anaerobes
H. influenzae
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)
Tx for periorbital cellulitis
clindamycin or amoxicillin +/- TMP-SMX
NO topical
etiology of orbital cellulitis
S. aureus S. pneumo anaerobes H. influenzae polymicrobial
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
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
Tx of orbital cellulitis
vanco + piper/tazo
surgery is indicated if poor response to antibiotics, worsening vision, evidence of abscess
