CNS Infections I Flashcards
clinical features of CNS infection
Fever, headache, altered mental status, or focal neurologic deficits
what are the routes of infections for CNS infections
- Hematogenous dissemination
- direct injury
- neural tissue (rare)
what is trojan horse
it is a method of microbes to spread through the blood where they infect WBCs then the WBC squeeze through the barrier to get into the cell
what is encephalitis and myelitis
encephalitis - inflammation of brain parenchyma
myelitis - infection of spinal cord
what are abscesses
localized infection in the brain or spinal cord
universal epidemiological considerations
age, season, geography, medical condition/underlying disease
how do you diagnose CNS infection
lumbar puncture and neuroimaging like CT or MRI (done before lumbar puncture)
what are some risks to doing a lumbar puncture
- headaches
- infection
- temporary pain or numbness to legs or lower back pain
- risk of bleeding into spinal canal
- ICP could be due to cerebral mass lesion and lumbar puncture –> brain herniation
normal pressure in the CSF
70-180mm H2O
how is a lumbar puncture performed
CSF is drawn from between two vertebrae with patient in the lateral decubitus position
appearance of normal and abnormal CSF
normal - clear, colorless
abnormal - cloudy/turbid
what are routine tests for CSF
WBC count with differential, RBC count, [Glucose], [protein], gram stain, bacteria culture
normal CSF value for WBC, RBC, glucose, protein
WBC - 0-5/mm3 for children and adults then 32/mm3 for neonates
RBC - none
glucose - 40-70mg/dL
protein: newborn is 150mg/dL and then from 6 months on it is 18-58mg/dL
typical findings in meningitis for bacteria: pressure, WBC count, cell differential, protein, glucose
pressure elevated WBC: greater than 1000/mm3 mainly neutrophils protein 100-500mg/dL glucose 0-10mg/dL
typical findings in meningitis for viral: pressure, WBC count, cell differential, protein, glucose
normal pressure WBC: less than 100/mm3 mainly lymphocytes protein 50-100mg/dL glucose 40-70mg/dL
typical findings in meningitis for fungal: pressure, WBC count, cell differential, protein, glucose
variable pressure variable WBC lymphocytes (and PMNs) protein 50-100mg/dL glucose less than 40mg/dL
typical findings in meningitis for tuberculosis: pressure, WBC count, cell differential, protein, glucose
variable pressure variable WBC lymphocytes protein 10-500mg/dL glucose 20-40mg/dL
clinical features of acute meningitis
- Onset: hours-several days
- Life-threatening
- Meningism: Fever, Headache, Nuchal rigidity, Nausea & Vomiting, Photophobia
- Altered mental status
features of aseptic meningitis
– Increased lymphocytes
– Self limiting
– Viral or non infectious (Absence of cultivable bacteria or fungi)
features of chronic meningitis
–rare
– Slow onset (period of weeks)
– ↓ Fever, lethargy
– TB, Fungi & (Protozoa)
tests for meningism
- Inability to flex neck (chin to chest)
- Inability to oppose nose with knee
- Tripod sign: Inability to sit up without using hands
- Kernig’s sign: inability to fully straighten leg when in laying position and leg is pulled up
- Brudzinski’s sign: child is flat on back and when neck pulled up, knees come up too
bacterial causes of meningitis in neonates and infants
neonates: S. agalactiae (group B strep) and E. coli, L. monocytogenes
infants: S. pneumonia (N. meningitides and H. influenza)
bacterial causes of meningitis in adolescents and adults
adolescents: S. pneumonia (N. meningitides and H. influenza)
adults: N. meningitides, S. pneumonia
bacterial causes of meningitis in adults greater than 50 years old
S. pneumonia (N. meningitides, L. monocytogenes and gram negs)
most frequently observed in children and adults with meningitis
Strep pneumonia
where is strep pneumonia found in the human body
throat and nasopharynx
strep pneumonia is associated with what conditions
previous pneumonia infections, otitis media, mastoiditis, sinusitus, endocarditis
basilar skull fracture and CSF leak is associated with what bacteria in association with bacterial meningitis
Strep pneumonia
what type of bacteria is strep pneumonia? where does it get its virulence?
gram positive diplococci
virulence from capsule, pneumolysin, IgA protease
clinical features of strep pnuemonia
rapid 1-2 days
impaired consciousness common
neisseria meningitides is most common in who
children and young adults
biological features of neisseria meningitides
- non motile gram neg diplococci (kidney bean shaped)
- 6 serotypes cause epidemics - A, B, C, W, X, Y
- higher in military recruit camps and schools
- fastidious and like high CO2 and must be grown on chocolate agar or martin-thayer agar
where does neisseria meningitides gets virulence factor from
capsule (serotype A, B, C, W-135, X, Y)
IgA protease
pili
LOS (lipooligosaccharide)
clinical features of neisseria meningitides
quick onset
acute photophobia
skin petechiae → ecchymoses/diffuse petechial rash - DIC
what test can be done on neisseria meningitides but is not 100% reliable
Tumbler test – put a glass firmly up to the rash and if you can see the rash clearly through the glass then the test is positive – seek help
prevention of neisseria meningitides
vaccination against serotype A, C, Y, and W135 which protects those 11-12 with a booster at age 16 but no protection against being a carrier
names of the neisseria meningitides vaccination
–US: meningococcal polysaccharide vaccine (MPSV4- Menomune®)
– meningococcal conjugate vaccine (MCV4-Menactra® & Menveo®)
