5/6 Brain Infections (Ch 26) Flashcards
what are the 4 cardinal manifestations of brain inflammation?
- fever
- headache
- altered mental status
- focal neuro signs
Define meningitis
- inflammation of the membranes of the brain or spinal cord.
- infection involving the subarachnoid and Virchow-Robin spaces (perivascular canals) over the surface of the brain
Define encephalitis
inflammation of the brain parenchyma
inside your brain, yo.
define myelitis
inflammation of the spinal cord
define encephalopathy
disorders/diseases of the brain that include non-infectious causes
why is the brain particularly vulnerable to poor outcomes from infection?
- brain has a narrow array of host defenses, and the BBB keeps usual defenses (antibodies, complement) from entering the brain space.
- limited drug penetration into CNS
- brain swelling -> further damage given the space constraints
Acute meningitis:
2 examples?
major symptoms?
Bacterial example: Meningococcus.
Aseptic example: Enterovirus
s/s: fever, headache, nuchal rigidity
Chronic meningitis: example? symptoms?
Ex: cryptococcus
can be asymptomatic or insidious
Acute encephalitis - hematogenous:
example? symptoms?
Ex: west nile virus
s/s: fever, ha, altered mental status
Acute encephalitis- neuronal
2 examples? symptoms?
Herpes simplex, Rabies
s/s: fever, ha, altered mental status
Chronic encephalitis: example? symptoms?
ex: syphilis
s/s: sensory changes, ataxia, dementia
Space occupying lesions:
2 examples?
symptoms for each?
- Brain abscess –> fever, ha, confusion, hemiparesis
- Epidural abscess –> fever, back pain, loss of leg strength/rectal tone/urinary continence
Toxin-mediated syndromes: 2 examples? s/s?
- Clostridium tetani (tetanus) –> NO FEVER, spastic paralysis
- Clostridium botulinum (botulism) –> NO FEVER, respiratory paralysis, cranial nerve paralysis
three causes of encephalitis?
what is their relative mortality?
- Arboviruses (fatal: 1-50%)
- Herpes simplex viruses (fatal: 70% untreated; 10% treated)
- Rabies (fatal: 99% without early PEP)
Clinical features of encephalitis? (laundry list)
Acute febrile illness with ha, altered mental status, focal neuro signs +/-
- behavior change, disorientation
- speech issues
- seizures
- motor weakness
- hyper-reflexia
- tremor
- pituitary involvement (hypothermia, diabetes insipidus, SIADH)
- myelitis (flaccid paralysis, bladder/bowel dysfxn, loss of deep tendon reflexes)
- raised intracranial pressure
Route of acquisition of viral encephalitis?
HSV and Rabies are acquired via neuronal transmission
Arboviruses (West Nile) are acquired hematogenously
Arboviral encephalitis: what are the most common mosquito-borne viruses in the US?
what animals are involved in their lifecycle?
West Nile Virus, Western equine, California encephalitis, St Louis encephalitis, Eastern equine encephalitis
Life cycle: host (birds) and vector (mosquitoes). humans and horses are accidental hosts: mosq bite -> viremia
West Nile Virus:
Clinical features?
- Pt will be ill 3-14 days after mosquito bite
- Most will get West Nile fever: fatigue, fever, ha, muscle weakness, rash (in half)
- Neuroinvasive disease (rare): encephalitis is most common.
West Nile: how to diagnose?
- Serology: PCR
- CSF: lymphocytic pleocytosis (=migraine + elevated WBCs), elevated protein; may see CSF antibody
- Imaging is often normal
- EEG may show general slowing
West Nile: treatment? prevention?
Treatment is supportive
Prevention: mosquito control and repellants
Herpes Simplex encephalitis: three possible routes for CNS infection?
These occur equally:
- Primary infection via oropharynx, via trigeminal nerve or olfactory tract. (generally in pts <18y)
- CNS invasion after recurrent HSV1 infection, viral reactivation with subsequent spread
- presumed reactivation of latent HSV in situ within CNS
Presentation of HSV1 encephalitis v HSV2 encephalitis?
HSV1: localized inflammation
HSV2: can be more generalised
HSV encephalitis: clinical features?
altered level of consciousness (96%)
fever (89%)
ha (78%)
personality change (61%)
seizures (38%)
Herpes simplex encephalitis: how to diagnose?
- CSF: high opening pressure, incr WBCs, many RBCs, glucose normal, raised protein
- PCR: pretty good sensitivity and specificity
- EEG
- MRI
- Biopsy
Herpes simplex encephalitis: treatment?
high dose IV acyclovir
Rabies: what is the reservoir? how is it transmitted?
Reservoir = mammals (wild animals: raccoons, skunks, foxes, dogs, bats)
transmitted via saliva
animal rabies is the major reservoir for human infection
most animals with rabies develop acute fatal encephalitis
Rabies transmission to humans: what % of bites transmit rabies?
more rare types of transmissions?
- 5-80% of bites result in transmission (ie we have no effing clue what this number is. presumably this accounts only for bites by a rabid animal but not specified)
- rarer transmission via animal scratches, mucous membrane exposures [omg how would that occur], unwitnessed bat bites, corneal transplant, lab accidents.
Rabies pathophys? how does it reach CNS?
- virus replicates in the muscle cells at the wound site.
- virus taken up by peripheral nerves, transported to CNS at rate of 8-20 mm/day
- serum antibody develops in 10 days (but cannot reach intraneural virus)
Rabies: incubation time from exposure to clinical disease?
Depends on inoculation distance from the CNS. Symptoms occur when virus reaches the spinal cord.
Rabies: two types of presentations? description of each?
- 80% of cases: “furious” encephalitic rabies. agitation, hydrophobia, salivation, arrythmias, coma, seiz, death
- 20%: Paralytic/dumb rabies: ascending paralysis, weakness, meningeal signs.
Rabies prevention?
- animal vaccination
- basic wound care for animal bites
- human vaccination (vets, travelers to highly endemic areas)
- post-exposure prophy with rabies vaccine and immunoglobulin
Post-infectious encephalomyelitis: define.
Post-infectious encephalomyelitis aka acute demyelinating encephalomyelitis (ADEM)
- autoimmune demyelinating disease, looks like acute viral encephalitis.
- may also have rash, fever, resp issues, GI illness.
- more common in children than adults
Post-infectious encephalomyelitis: findings on CSF or MRI?
- CSF: normal/nonspecific
- MRI: enhancing multifocal white matter disease c/w (consistent with??) demyelination
what are the 2 main “space-occupying lesions” in the brain?
Brain abscess, malignancy
Brain abscess: pathophys?
- local extension of an existing infection
- hematogenous spread
Bacterial brain abscess: risk factors?
otitis media
mastoiditis
sinusoiditis
dental sepsis
penetrating trauma
congenital heart disease
bacterial lung inf
bacterial endocarditis
immunocompromised patients
Diagnosis of space occuping lesions? (ie brain abscess, malignancy)
-Imaging = critical
- Drainage, tissue diagnosis, culture -> antibiotic
- Empiric therapy for presumed bacterial abscess: “Vanco/ceftriaxone/metronidazole directed at mouth, URI, bacteremia pathogens”
- If HIV: empiric treatment for toxoplasma
