CNS infections Flashcards Preview

IDMM > CNS infections > Flashcards

Flashcards in CNS infections Deck (39):
1

What are the possible causes of meningitis?

Bacteria: S. pneumo, N. meningitidis, GBS, H. influenzae, Listeria

Viral: Enterovirus (95%), Herpesvirus (VZV, HSV)

Fungal: Coccidiodes immitis, Crytococcus neoformans (immune compromise ONLY)

Mycobacterium tuberculosis

2

What are the possible routes of entry for a pathogen into the CNS?

Blood-->CSF (meningitis)

Blood-->brain (encephalitis)

Local invasion (bacteria)

Nerve invasion (VSZ, HSV)

Direct inoculation (surgery)

3

What is the prevalence of bacterial and viral meningitis?

Viral: 11-27/100 000

Bacterial: 3/ 100 000 **viral is 4-8 times more common

4

What pathogens are more likely to cause neonatal meningitis vs. paediatric or adult meningitis?

Neonatal: GBS is most likely (can be caused by others too)

Paeds + adult: S. pneumo, N. meningitidis are most common. Others can cause it too.

5

What is the basic pathophysiology of meningitis?

Pathogen causes inflammation in the CSF--> hydrocephalus--> increased intracranial pressure--> decreased cerebral perfusion

6

What is Kernig's sign, Brudzinski's sign and jolt accentuation?

Kernig's sign: supine patient, hips flexed at 90 degrees, when you try and extend the knees there is pain/resistance.

Brudzinsky's sign: passive flexion of the neck causes flexion of the hips +/- knees

Jolt accentuation: ask the patient to rotate head side to side (shake head "no") 2-3 times per second. If the headache worsens this is a positive sign.

7

What time is year is more likely for a case of viral meningitis? Bacterial?

Viral: summer/fall

Bacterial: no seasonality

8

What kind of meningitis gives a rash? What kind of rash is it classically?

Menningicoccal meninigitis: petechial rash on the limbs, advances to purpura.

9

When/where would you see fungal meningitis?

Coccidiodes immitis: in the southwest US. 1% of infections progress to this.

Cryptococcus neoformans: occurs in immune deficient hosts.

10

When/where would you see tuberculous meningitis?

In areas with a high prevalence of TB. Most are associated with TB infection elsewhere or miliary TB, but this may not always be detectable

11

What are indications for doing a CT before doing a lumbar puncture?

-if there is neurological involvement, or history of neurological problems, or high intracranial pressure (papilledema)

12

What are the signs and symptoms of meningitis? What is the classic triad? Can viral and bacterial meningitis be differentiated based on S/S?

Classic triad: nucal rigidity, altered mental status, fever.

Symptoms: headache, photophobia, nausea, rash, lethargy

Signs: kernig's, brudzinski's, jolt accentuation

**viral and bacterial cannot be differentiated based on symptoms, but viral meningitis tends to be milder**

13

What is the empiric therapy for meningitis?

ceftriaxone + vancomycin +/- ampicillin +/- dexamethasone

14

What are the CSF characteristics of viral and bacterial meningitis? (cell #, WBC differential, protein, glucose, Gram stain, culture, PCR)

A image thumb
15

What are the basic principles of diagnosis and treatment in meningitis? (flowchart..)

A image thumb
16

How to differentiate between meningitis and encephalitis?

Since encephalitis is inflammation of the brain parenchyma, abnormalities in brain function will definitely be present (e..g mental status, sensor deficits, change in behaviour or personality). 

17

Define meningitis, encephalitis, and meniogoencephalitis

Meningitis: inflammation of the meninges

Encephalitis: inflammation of the brain parenchyma

Meningoencephalitis: inflammation of both

18

What are the causes of encephalitis?

Infectious

viral

  • infectious (HSV, VZV, CMV, EBV, enterovirus, measles, arboviruses, mumps, rubella, polio, rabies, west nile)
  • post-infectious encephalitis (Acute disseminated encephalomyelitis)

non-viral 

  • bacterial (syphillis, TB, Borellia (ticks))
  • fungal (cryptococcus, toxoplasmosis in immunecompromised)
  • Parasitic (African trypanosomiasis, Naegleria fowleri-->ameoba that lives in warm, fresh water)

Non- infectious

  • tumours
  • vasculitis
  • drug-induced
  • trauma
  • auto-immune (Lupus, Behcets)
  • etc..

19

What encephalitis pathogens do the following point to:

  • Bats
  • Birds
  • Cats
  • Mosquitos
  • Ticks
  • Unpasteurized milk

Bats: rabies
Birds: west nile

Cats: toxoplasmosis

Mosquitos: west nile, other arboviruses, plasmodium
Ticks: Borellia (lyme disease)
Unpasteurized milk: Brucella, Listeria monocytogenes

20

In a patient with suspected infectious encephalitis, what questions are important in the history? Why?

Travel history (e.g. Africa -> plasmodium, African trypanosomiasis)

Sexual history (syphillis)

Animal/Insect exposures (bats, cats, birds, insects)

Unpasteurized food (unpasteurized milk products)

Season of the year (seasonality of some agents)

Age (west nile)

Vaccination history (measle, mumps, VZV)

21

Mnemonic for encephalitis differential

HE'S LATIN AMERICAN

Herpesviridae

Enteroviridae (esp. polio)

Slow viruses (JC virus, prions)

Syphillis

Legionella/Lyme disease/Lymphocytic meningoencephalitis

Aspergillus

Toxoplasmosis

Intracranial pressure

Neisseria meningitidis

Arboviridae

Measles/Mumps/Mycobacterium TB/Mucor

E. coli

Rabies/Rubella

Idiopathic

Cryptoccocus/Candida

Abscess

Neoplasm/Neurocysticercosis

22

What is ADEM?

Acute desseminated encephalomyelitis

  • Immune mediated
  • usually happens post viral infection

23

What is the general pathophysiology of encephalitis?

Inflammation of the brain parenchyma. Can be necrotizing, can cause hemorrhage, can destroy neurons and cause brain damage. 

24

Clinical manifestations of encephalitis. Can infectious and non-infectious be distinguished based on the symptoms?

  • Fever
  • Headache
  • Cognitive dysfunction (speech, memory, behaviour, personality, confusion, agitation, unresponsiveness)
  • Seizures
  • +/- rash

 

Cannot distinguish infectious from non-infectious based on clinical manifestations alone. 

25

On the physical exam of a patient with encephalitis, what do the following indicate:

  • flaccid paralysis -->encephalitis?
  • tremors (eyelids, tongue, lips, extremities)
  • hydrophobia, aerophobia, pharyngeal spasm
  • vesicular rash

  • flaccid paralysis -->encephalitis--> west nile
  • tremors (eyelids, tongue, lips, extremities)--> west nile
  • hydrophobia, aerophobia, pharyngeal spasm-->rabies
  • vesicular rash-->VZV

26

Diagnostic approach to encephalitis

  • S/S
  • Physical exam
  • LP with CSF analysis (including PCR, culture)
  • Serology
  • MRI (temporal lobe inflammation typical of HSV)

27

Treatment of HSV encephalitis

acyclovir 

28

What is a brain abscess? How does it occur? What are predisposing factors?

A focal, encapsulated collection of suppurative fluid. Local or hematogenous spread of a pathogen.

There are usually one of more predisposing factors:

  • immunesuppresion
  • chronic cardiopulmonary conditions (e.g. congenital heart abnormalities)
  • penetrating head trauma
  • local infection (osteomyelitis, otitis media, sinusitis)
  • distant infection

29

What are the causative agents of brain abscess in an immuncompetent and immunocompromised host?

Immunocompetent: polymicrobial (Strep anginosus, Anaerobes, S. aureus)

Immunocompromised: parasite (toxoplasmosis), fungal (crytptococcus neoformans, mycobacterial (TB))

30

What are the clinical manifestations of brain abscess?

headache localized to side of abscess

fever

focal neurologic deficit (depending on location in brain)

mental status changes

seizures

nausea

nuchal rigidity (sometimes)

31

Diagnostic approach to brain abscess

  • S/S
  • Physical exam
  • CBC may have elevated WBC
  • CT/MRI
  • LP is contraindicated because of focal headache and focal neurological involvement

32

What is the treatment for a brain abscess?

  • aspiration of abscess
  • empiric antibiotics (ceftriaxone +metronidazole +/- vancomycin OR meropenem +/- vancomycin)
  • glucocorticoids if swelling (dexamethasone

33

How common are brain abscesses?

Not common! Only 0.3-1.5/100 000 people per year

34

What is an epidural abscess? How common is it?

A focal collection of suppurative fluid in the epidural space (outside the dura, between the dura and the bone).

Classified as intracranial and spinal (9x more common)

Very uncommon (2-25/100 000 hospital admissions)

 

35

What are the risk factors for epidural abscess?

  1. Epidural manipulation (catheter in obstetrics, paraspinal injections)
  2. Contiguous bony or soft tissue infections
  3. bacteremia
  4. trauma

36

What are the main pathogens involved in epidural abscesses?

S. aureus (63%)

gram negative bacilli (16%)

streptococci (9%)

37

What is the general pathophysiology of a spinal epidural abscess?

  • the abscess compresses the spinal cord, cuts off blood supply.
  • bacterial toxins mediate inflammation

38

What is the clinical presentation of an epidural abscess?

Classic triad:

  • fever
  • back pain
  • neurological deficits

39

What is the diagnostic approach to an epidural abcess?

  • S/S: the triad
  • physical exam
  • diagnostic imaging (MRI is best, then CT, then Xray)
  • Analysis of abcess fluid
  • Empric antibiotic treatment (ceftriaxone +metronidazole + vancomycin)
  • Surgical decompression and drainage