5/6 Brain Infections (Ch 26) Flashcards by Jennifer Cromwell

what are the 4 cardinal manifestations of brain inflammation?

fever
headache
altered mental status
focal neuro signs

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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

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Define encephalitis

inflammation of the brain parenchyma

inside your brain, yo.

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define myelitis

inflammation of the spinal cord

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define encephalopathy

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

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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

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Acute meningitis:

2 examples?

major symptoms?

Bacterial example: Meningococcus.

Aseptic example: Enterovirus

s/s: fever, headache, nuchal rigidity

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Chronic meningitis: example? symptoms?

Ex: cryptococcus

can be asymptomatic or insidious

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Acute encephalitis - hematogenous:

example? symptoms?

Ex: west nile virus

s/s: fever, ha, altered mental status

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Acute encephalitis- neuronal

2 examples? symptoms?

Herpes simplex, Rabies

s/s: fever, ha, altered mental status

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Chronic encephalitis: example? symptoms?

ex: syphilis

s/s: sensory changes, ataxia, dementia

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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

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

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

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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)

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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

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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?

1. 80% of cases: **"furious" encephalitic rabies**. agitation, hydrophobia, salivation, arrythmias, coma, seiz, death 2. 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**