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The ultimate test - Last Keystone exam > CNS infections > Flashcards

CNS infections Flashcards

1
Q

What are the unique aspects of the CNS relevant to infections?

A
  • no regeneration capacity
  • fixed space (absence of drainage mechanism)
  • blood brain barrier
  • lack of WBCs (microglia replace them)
  • very specific function in each region
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2
Q

Function of BBB in CNS infections

A

Normally, Protects the CNS from acute physiologic status change and toxin exposure.
** Inflammation (due to cytokines) increases the permeability of the BBB to certain antibiotics!!

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3
Q

3 routes of infection into the CNS

A
  • Hematogenous (vast majority of community acquired bacterial CNS infections)
  • Contiguous (from neighboring anatomical site (eg, trauma to skull, severe sinus infection)
  • Ascending (from peripheral nervous system, eg HSV)
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4
Q

What 2 kinds of organisms have the ability to survive in bloodstream and stick to the meninges/brain?

A
  • encapsulated organisms

- intracellular organisms (listeria and viruses)

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5
Q

Which encapsulated organisms are capable of infecting the CNS?

A
  • Neisseria meningitidis
  • streptococcus pneumoniae
  • H. influenzae
  • Cryptococcus neoformans
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6
Q

What mechanism is the cause of neck stiffness and positive Kernig/Brudzinski sign in meningitis?

A

Inflammation!

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7
Q

Why does headache/back pain occur in CNS infection?

A

increased intracranial pressure.

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8
Q

What is the jolt accentuation sign for meningitis?

A

It is when you shake someone’s head, and it is positive if their headache gets worse.

Very sensitive, but not very specific.

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9
Q

Key parts of the physical exam for CNS infection

A
  • meningeal irritation (Kernig/brudzinski/neck stiff)
  • intracranial hypertension (fundoscopic exam)
  • focal neurologic sign (neuro exam)

**REPEAT these tests over a few hours in pt’s you are concerned about.

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10
Q

Appearance of papilledema

A

fuzzy optic disc, as opposed to the normal, clearly demarcated disc.

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11
Q

What is the single most important diagnostic test for meningitis?

A

lumbar puncture. Do it whenever meningitis or encephalitis is suspected clinically.

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12
Q

contraindications for lumbar puncture -4

A
  • intracranial mass lesion
  • intracranial hypertension
  • severe thrombocytopenia (bleeding)
  • agitated patient
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13
Q

When should a CT scan (with contrast) be used before lumbar puncture?

A

A CT scan can determine that a lumbar puncture is safe.

  • any focal neurologic sign
  • any known intracranial pathology
  • immunocompromised host
  • papilledema

**These are all signs of possible intracranial mass (first 3) or elevated intracranial pressure (papilledema)

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14
Q

You suspect meningitis. What is the next step?

A

First, do a rapid physical exam get blood culture.

-Then, do a lumbar puncture and start empiric antibiotics.

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15
Q

When is a brain / meningeal biopsy used?

A
  • as a last resort

- most commonly used to differentiate chronic infection vs. tumor

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16
Q

4 most common symptoms of bacterial meningitis

A
  • headache
  • fever
  • nuchal rigidity
  • altered mental status
17
Q

T/F - Meningitis is clinically indistinguishable from other forms of sepsis in a neonate.

A

True. Suspect meningitis in any febrile illness in a newborn!

18
Q

Normal CSF labs vs. Bacterial Meningitis vs. viral meningitis

A

Normal - 0-5 WBCs, glucose 40-80, predominantly mononuclear cells.

Bacterial - 1000-5000 WBCs, glucose 40, predominantly mononuclear cells

19
Q

two common meningitis pathogens for birth - 2 years old

A

Group B strep

E coli

20
Q

Two common meningitis pathogens for 2 years old to 50 years old

A

Strep pneumo

Neisseria meningitidis

21
Q

Empiric antibiotic therapy for meningitis in age group -

A

Ampicillin (for listeria)
+
third gen cephalosporin

(all intravenous!)

22
Q

Empiric antibiotic therapy for meningitis in age group - 1-23 months

A

Vancomycin
+
third gen cephalosporin

(all intravenous!)

23
Q

Empiric antibiotic therapy for meningitis in age group - 2-50 years

A

Vancomycin
+
third gen cephalosporin

(all intravenous!)

24
Q

Empiric antibiotic therapy for meningitis in age group - >50 years.

A 
Vancomycin 
\+
third gen cephalosporin 
\+ 
ampicillin (for listeria)

(all intravenous!)

25
Q

Use of steroids in meningitis

A

Indicated for practically all suspected bacterial meningitis. HOWEVER - you must start it at the same time as antibiotics.

26
Q

How do steroids help in meningitis?

A

they suppress severe inflammatory reaction in the CSF space, reducing damage from the infection.

27
Q

Most common cause of encephalitis

A

Viruses.

28
Q

Treatable causes of encephalitis

A
  • HSV
  • bacterial

Most causes are not treatable

29
Q

When should you suspect encephalitis?

A
  • any unexplained brain parenchymal lesion

- especially when it is not consistent with neurovascular anatomy.

30
Q

Presentation of HSV encephalitis

A

-Fever and personality change

31
Q

Treatment for HSV encephalitis

A

high dose acyclovir

32
Q

You suspect encephalitis. What is the next step?

A
  • Start acyclovir immediately, without waiting for test results!!
  • Any pt with encephalitis needs to be considered to have HSV until proven otherwise.
33
Q

Diagnostic test for HSV encephalitis

A

PCR on CSF fluid - very sensitive/specific.

34
Q

Important consideration for empiric therapy in brain abscess

A

look for the primary site of infection - this can help you start appropriate therapy.

35
Q

T/F if you suspect brain abscess, you should do a CT without contrast

A

False. with contrast

36
Q

You suspect a brain abscess. What should you do and why?

A

Call Neurosurgery!
they can help with:
-possible drainage
-aspiration to establish diagnosis.

37
Q

Who does listeria monocytogenes infect (for meningitis)

A

the very young (newborns) and the old

38
Q

how to treat listeria monocytogenes?

A

ampicillin

The ultimate test - Last Keystone exam (30 decks)

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