5/6 Brain Infections (Ch 26)

Question 1

what are the 4 cardinal manifestations of brain inflammation?

Answer 1

• fever
• headache
• altered mental status
• focal neuro signs

Question 2

Define meningitis

Answer 2

• 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

Question 3

Define encephalitis

Answer 3

inflammation of the brain parenchyma

inside your brain, yo.

Question 4

define myelitis

Answer 4

inflammation of the spinal cord

Question 5

define encephalopathy

Answer 5

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

Question 6

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

Answer 6

• 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

Question 7

Acute meningitis:

2 examples?

major symptoms?

Answer 7

Bacterial example: Meningococcus.

Aseptic example: Enterovirus

s/s: fever, headache, nuchal rigidity

Question 8

Chronic meningitis: example? symptoms?

Answer 8

Ex: cryptococcus

can be asymptomatic or insidious

Question 9

Acute encephalitis - hematogenous:

example? symptoms?

Answer 9

Ex: west nile virus

s/s: fever, ha, altered mental status

Question 10

Acute encephalitis- neuronal

2 examples? symptoms?

Answer 10

Herpes simplex, Rabies

s/s: fever, ha, altered mental status

Question 11

Chronic encephalitis: example? symptoms?

Answer 11

ex: syphilis

s/s: sensory changes, ataxia, dementia

Question 12

Space occupying lesions:

2 examples?

symptoms for each?

Answer 12

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

Question 13

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

Answer 13

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

Question 14

three causes of encephalitis?

what is their relative mortality?

Answer 14

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

Question 15

Clinical features of encephalitis? (laundry list)

Answer 15

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

Question 16

Route of acquisition of viral encephalitis?

Answer 16

HSV and Rabies are acquired via neuronal transmission

Arboviruses (West Nile) are acquired hematogenously

Question 17

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

what animals are involved in their lifecycle?

Answer 17

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

Question 18

West Nile Virus:

Clinical features?

Answer 18

• 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.

Question 19

West Nile: how to diagnose?

Answer 19

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

Question 20

West Nile: treatment? prevention?

Answer 20

Treatment is supportive

Prevention: mosquito control and repellants

Question 21

Herpes Simplex encephalitis: three possible routes for CNS infection?

Answer 21

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

Question 22

Presentation of HSV1 encephalitis v HSV2 encephalitis?

Answer 22

HSV1: localized inflammation

HSV2: can be more generalised

Question 23

HSV encephalitis: clinical features?

Answer 23

altered level of consciousness (96%)

fever (89%)

ha (78%)

personality change (61%)

seizures (38%)

Question 24

Herpes simplex encephalitis: how to diagnose?

Answer 24

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

Question 25

Herpes simplex encephalitis: treatment?

Answer 25

high dose IV acyclovir

Question 26

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

Answer 26

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

Question 27

Rabies transmission to humans: what % of bites transmit rabies? more rare types of transmissions?

Answer 27

- 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.

Question 28

Rabies pathophys? how does it reach CNS?

Answer 28

- 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)

Question 29

Rabies: incubation time from exposure to clinical disease?

Answer 29

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

Question 30

Rabies: two types of presentations? description of each?

Answer 30

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

Question 31

Rabies prevention?

Answer 31

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

Question 32

Post-infectious encephalomyelitis: define.

Answer 32

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

Question 33

Post-infectious encephalomyelitis: findings on CSF or MRI?

Answer 33

- CSF: normal/nonspecific - MRI: enhancing multifocal white matter disease c/w (consistent with??) **demyelination**

Question 34

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

Answer 34

Brain abscess, malignancy

Question 35

Brain abscess: pathophys?

Answer 35

- local extension of an existing infection - hematogenous spread

Question 36

Bacterial brain abscess: risk factors?

Answer 36

otitis media mastoiditis sinusoiditis dental sepsis penetrating trauma congenital heart disease bacterial lung inf bacterial endocarditis immunocompromised patients

Question 37

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

Answer 37

**-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**