what are the 4 cardinal manifestations of brain inflammation?
-altered mental status
-focal neuro signs
-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
inflammation of the brain parenchyma
inside your brain, yo.
inflammation of the spinal cord
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
Bacterial example: Meningococcus.
Aseptic example: Enterovirus
s/s: fever, headache, nuchal rigidity
Chronic meningitis: example? symptoms?
can be asymptomatic or insidious
Acute encephalitis - hematogenous:
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?
s/s: sensory changes, ataxia, dementia
Space occupying lesions:
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
-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:
-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?
-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%)
personality change (61%)
Herpes simplex encephalitis: how to diagnose?
-CSF: high opening pressure, incr WBCs, many RBCs, glucose normal, raised protein
-PCR: pretty good sensitivity and specificity
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?
1. 80% of cases: "furious" encephalitic rabies. agitation, hydrophobia, salivation, arrythmias, coma, seiz, death
2. 20%: Paralytic/dumb rabies: ascending paralysis, weakness, meningeal signs.
-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?
-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
Bacterial brain abscess: risk factors?
congenital heart disease
bacterial lung inf
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