5/6 Brain Infections (Ch 26) Flashcards Preview

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Flashcards in 5/6 Brain Infections (Ch 26) Deck (37)

what are the 4 cardinal manifestations of brain inflammation?



-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


-motor weakness



-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






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



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