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5/6 Brain Infections (Ch 26) Flashcards

1
Q

what are the 4 cardinal manifestations of brain inflammation?

A
  • fever
  • headache
  • altered mental status
  • focal neuro signs
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2
Q

Define meningitis

A
  • 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
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3
Q

Define encephalitis

A

inflammation of the brain parenchyma

inside your brain, yo.

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4
Q

define myelitis

A

inflammation of the spinal cord

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5
Q

define encephalopathy

A

disorders/diseases of the brain that include non-infectious causes

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6
Q

why is the brain particularly vulnerable to poor outcomes from infection?

A
  • 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
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7
Q

Acute meningitis:

2 examples?

major symptoms?

A

Bacterial example: Meningococcus.

Aseptic example: Enterovirus

s/s: fever, headache, nuchal rigidity

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8
Q

Chronic meningitis: example? symptoms?

A

Ex: cryptococcus

can be asymptomatic or insidious

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9
Q

Acute encephalitis - hematogenous:

example? symptoms?

A

Ex: west nile virus

s/s: fever, ha, altered mental status

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10
Q

Acute encephalitis- neuronal

2 examples? symptoms?

A

Herpes simplex, Rabies

s/s: fever, ha, altered mental status

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11
Q

Chronic encephalitis: example? symptoms?

A

ex: syphilis

s/s: sensory changes, ataxia, dementia

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12
Q

Space occupying lesions:

2 examples?

symptoms for each?

A
  • Brain abscess –> fever, ha, confusion, hemiparesis
  • Epidural abscess –> fever, back pain, loss of leg strength/rectal tone/urinary continence
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13
Q

Toxin-mediated syndromes: 2 examples? s/s?

A
  • Clostridium tetani (tetanus) –> NO FEVER, spastic paralysis
  • Clostridium botulinum (botulism) –> NO FEVER, respiratory paralysis, cranial nerve paralysis
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14
Q

three causes of encephalitis?

what is their relative mortality?

A
  • Arboviruses (fatal: 1-50%)
  • Herpes simplex viruses (fatal: 70% untreated; 10% treated)
  • Rabies (fatal: 99% without early PEP)
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15
Q

Clinical features of encephalitis? (laundry list)

A

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
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16
Q

Route of acquisition of viral encephalitis?

A

HSV and Rabies are acquired via neuronal transmission

Arboviruses (West Nile) are acquired hematogenously

17
Q

Arboviral encephalitis: what are the most common mosquito-borne viruses in the US?

what animals are involved in their lifecycle?

A

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

18
Q

West Nile Virus:

Clinical features?

A
  • 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.
19
Q

West Nile: how to diagnose?

A
  • Serology: PCR
  • CSF: lymphocytic pleocytosis (=migraine + elevated WBCs), elevated protein; may see CSF antibody
  • Imaging is often normal
  • EEG may show general slowing
20
Q

West Nile: treatment? prevention?

A

Treatment is supportive

Prevention: mosquito control and repellants

21
Q

Herpes Simplex encephalitis: three possible routes for CNS infection?

A

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
22
Q

Presentation of HSV1 encephalitis v HSV2 encephalitis?

A

HSV1: localized inflammation

HSV2: can be more generalised

23
Q

HSV encephalitis: clinical features?

A

altered level of consciousness (96%)

fever (89%)

ha (78%)

personality change (61%)

seizures (38%)

24
Q

Herpes simplex encephalitis: how to diagnose?

A
  • CSF: high opening pressure, incr WBCs, many RBCs, glucose normal, raised protein
  • PCR: pretty good sensitivity and specificity
  • EEG
  • MRI
  • Biopsy
25
Q

Herpes simplex encephalitis: treatment?

A

high dose IV acyclovir

26
Q

Rabies: what is the reservoir? how is it transmitted?

A

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

27
Q

Rabies transmission to humans: what % of bites transmit rabies?

more rare types of transmissions?

A
  • 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.
28
Q

Rabies pathophys? how does it reach CNS?

A
  • 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)
29
Q

Rabies: incubation time from exposure to clinical disease?

A

Depends on inoculation distance from the CNS. Symptoms occur when virus reaches the spinal cord.

30
Q

Rabies: two types of presentations? description of each?

A
  1. 80% of cases: “furious” encephalitic rabies. agitation, hydrophobia, salivation, arrythmias, coma, seiz, death
  2. 20%: Paralytic/dumb rabies: ascending paralysis, weakness, meningeal signs.
31
Q

Rabies prevention?

A
  • animal vaccination
  • basic wound care for animal bites
  • human vaccination (vets, travelers to highly endemic areas)
  • post-exposure prophy with rabies vaccine and immunoglobulin
32
Q

Post-infectious encephalomyelitis: define.

A

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
33
Q

Post-infectious encephalomyelitis: findings on CSF or MRI?

A
  • CSF: normal/nonspecific
  • MRI: enhancing multifocal white matter disease c/w (consistent with??) demyelination
34
Q

what are the 2 main “space-occupying lesions” in the brain?

A

Brain abscess, malignancy

35
Q

Brain abscess: pathophys?

A
  • local extension of an existing infection
  • hematogenous spread
36
Q

Bacterial brain abscess: risk factors?

A

otitis media

mastoiditis

sinusoiditis

dental sepsis

penetrating trauma

congenital heart disease

bacterial lung inf

bacterial endocarditis

immunocompromised patients

37
Q

Diagnosis of space occuping lesions? (ie brain abscess, malignancy)

A

-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

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