Week 2 - A. Prunuske Flashcards
What are the “Big Three” symptoms that CNS infections share in common?
- Fever
- Headache
- Altered Mental State
What are the noninfectious causes of fever, headache, and altered mental state?
- Subarachnoid hemorrhage
- Inflammatory disease (e.g. lupus)
- Neoplasm
- Metabolic disorder
- Drug (e.g. NSAIDs)
What are the infectious causes of fever, headache, and altered mental status?
- Meningitis
- Encephalitis
- Abscess
What part of the brain does meningitis occur?
Subarachnoid space
What part of the brain does encephalitis occur?
diffuse parenchyma
What part of the CNS does myelitis occur?
spinal cord
What type of meningitis is most common?
Viral
What type of meningitis is most life-threatening?
Bacterial
When do fungi or protozoa cause meningitis?
patient is immunocompromised
What virulence factor allows pathogens to evade immune system and cause meningitis?
Capsules
What additional symptom is common in meningitis?
Nuchal rigidity (stiff neck)
What additional symptoms are seen in Encephalitis that are not seen in Meningitis?
- Motor and sensory deficits
- Seizures
- Speech disturbances
- Lethargy
- Coma
What are common viral causes of Encephalitis?
- Enterovirus
- Arbovirus
- Herpes
- Rabies
What are common non-viral causes of Encephalitis?
- Rickettsia
- Mycoplasma
- Acute disseminated encephalomyelitis (ADEM)
What is a brain abscess?
Focal infection of parenchyma
What is the typical problem leading to brain abscess?
- Pre-existing ischemia
- Necrosis begins as cerebritis
- Area becomes encapsulated
What are common conditions that can lead to brain abscess?
- Otitis media –> temporal lobe/cerebellum
- Dental/sinus infection –> frontal lobe
- Hematogenous –> multiple, territory of middle cerebral artery
- Trauma
What happens if a brain abscess ruptures?
Meningitis! (scary)
What five clinical features are common in Encephalitis but not Encephalopathy?
Common in Encephalitis (not Encephalopathy):
- Fever
- Headache
- Seizures
- Leukocytosis in CBC
- Pleocytosis in CSF (increased WBC’s)
Why are infections of the CNS uncommon?
- Scalp/skull protects
- Three meningeal layers surround brain/spinal cord
- Tight-jxns in BBB prevent organisms from entering
- Vaccination
What two cells are innate immune cells in the CNS?
- Microglia (macrophages in the brain)
- Astrocytes
What are the basic pathways of introducing pathogens to the CNS?
- Placental-fetal (milk)
- Respiratory
- Sexual
- Oral
- Zoonotic
- Blood transfusion
- Trauma
What components of a patient’s history are important for diagnosing pathogen/CNS infection?
- Travel history
- Recent trauma
- Living conditions
- Season
- Immunosuppressants (Prednisone)
What is the clinical course if CNS infection is speculated?
- H & P
- Blood culture then start antibiotic Tx
- Neuroimaging
- LP/biopsy
- Identify organism - Gram stain, PCR, RT-PCR
- Switch to definitive Tx based on antibiotic susceptibility tests and/or supportive therapy
Are most CNS infections acute or chronic?
ACUTE!!!
What should you do if you suspect bacterial meningitis?
***Start IMMEDIATE treatment!
What antibiotic properties would be important to consider for a CNS infection?
- Can cross BBB
- Small
- Lipophilic
- Not effluxed
- low affinity for plasma binding proteins
- Bactericidal
- Broad spectrum
What drug, besides antibiotics, is also important to give when treating a CNS infection?
Dexamethasone
(decreases inflammation in subarachnoid space)
If a focal mass lesion is found on neuroimaging (CT/MRI), what test should not be done? Why?
LP!
Because of risk of brain herniation occuring.
In the case of meningitis, what would a head CT show? MRI?
CT: nothing, NORMAL!
MRI: leptomeningeal enhancements, but no focal lesions.
What immune function does the subarachnoid space lack when fighting meningitis?
Antibody and Complement production required for phagocytosis.
What are 11 possible clinical symptoms a patient with meningitis could present with?
- Fever (older individuals less likely)
- Headache
- Altered mental status
- Nuchal rigidity (30% cases)
- Photophobia
- Rash
- Nausea
- Vomiting
- Diarrhea
- Anorexia
- Upper respiratory symptoms
What type of meningitis usually shows high presence of PMN’s on CSF from LP?
Bacterial meningitis
What three symptoms are common in Aseptic Meningitis Syndrome?
- Fever
- Headache
- Photophobia
(less neck stiffness/altered mental status)
What are the typical CSF findings in the case of Aseptic Meningitis Syndrome?
- Increase in lymphocytes and monocytes
- Slight increase in protein
- Normal glucose
What are the typical CSF findings in bacterial meningitis?
- High opening pressure
- High WBC count
- >80% PMN’s on WBC differential
- High protein
- Low glucose
What is the treatment for Aseptic Meningitis Syndrome?
Supportive therapy & recover on their own
(unless neonatal)
What age has the highest incidence of Aseptic Meningitis Syndrome?
0-1 yoa
(first year of life)
85% of viral meningitis cases are associated with what type of virus?
Enteroviruses
(RNA viruses)
How do you treat bacterial meningitis?
-
Immediate empiric treatment with Ceftriaxone (3rd generation cephalosporin)
- 3 hr delay leads to increase in 3 month fatality
If you suspect a patient with bacterial meningitis to have a risk of other pathogen agents, how do you treat them?
- Risk of other agents, then add:
- MRSA - Vancomycin
- HSV-2 - Acyclovir
- Pseudomonas - Cefepime (4th generation cephalosporin)
- Listeria - Ampicillin
Which bacterial pathogen most commonly causes bacterial meningitis in adults?
Streptococcus pneumonia
What pathogen most commonly causes bacterial meningitis in 11-17 year olds?
Neisseria meningiditis
Because their risk is 10x higher than other adults, what should all adults over age 65 receive?
13-valent pneumococcal conjugate vaccine
What are the 9 steps in the development of bacterial meningitis by H. influenza type b, and N. meningiditis, Strept. pneumonia?
- Mucosal colonization at nasopharynx
- Invasion and multiplication in bloodstream
- Cross BBB
- Egress into CSF
- Astrocytes and microglia release inflammatory cytokines in CSF
- Increased permeability of BBB
- Diapedesis of leukocytes into CSF
- Edema and increased intracranial pressure
- Neuronal injury including hearing loss (CN VIII)
