CNS infections Flashcards
cellular response to pathogens
neutrophils = acute
lymphocytes and macrophages with chronic infections, esp. viruses and yeasts
multinucleated giant cells with specific chronic infections
very important complications of CNS infections
cerebral edema, blocked CSF pathways–> herniation, death,
or permanent brain damage
Portals of entry into the CNS
hematogenous- usually bateremia/viremia in systemic infection or by septic emboli
2. local extension from mastoid, middle ear, paranasal sinuses, osteomyelitis of skull/vertebrae
direct implantations from penetrating wounds; compound fractures.
axonal transport- olfactory for herpes; peripheral nerves for rabies
macroscopic and microscopic views of bacterial meningitis
purulent meningitis over convexities with acute inflammation and vasculitis
Common bacteria that cause bacterial meningits
neonates: group B strep, e. coli, lysteria monocytogenes
babies: group b strep, staphlococci
young adults: neisseria meningitides
adults, esp. older adults: Strep pneumoniae, L monocytogenes
What bacterial pathogens cause meningitis in normal individuals?
Hib, S. pneumoniae, N. meningitides
What are differences btw meningitis seen in premies and in full term neonates
full-term neonates usually show immediate meningitis, esp. following complicated labor, with E coli and group B strep
premies show group B strep and staph
What organisms are splenectomized ppl esp. susceptible to?
S. pneumonia
what are some gross features of bacterial meningitis?
purulent exudate on sulcal vessels, turbid ventricular fluid, pus on ependymal lining
What are the histologic features of bacterial meningitis?
at first, all neutrophils (in contrast to viral meningitis, which is usually aseptic with few neutrophils). then lymphocytes and macrophages, then plasma cells and fibroblasts. a few cortical microinfarcts.
Complications meningitis in kids
intellectual disability, sensorineural deafness, subdural effusion (aka hygroma), and epilepsy, and hydrocephalus (subdural effusion and hydrocephalus most important). secondary vasculitis/thrombophlebitis of dural sinuses may also cause infarction, which results in major neurologic deficits.
Waterhouse-Friderchsen syndrome
meningitis with fulminating course. disseminated intravascular coagulation. CNS shows only petechiae and congestion.
Empyema
uncommon subdural abscess usually caused by infections that got in via direct or local routes. esp. seen in staph and strep. this is very serious- may stread over wide areas, and hard to treat because the area isn’t vascularized
common locations of brain abscesses depending on route of infection
hematogenous spread: grey/white junction or in distribution of the MCA
direct spread: frontal or temporal lobes. frontal from dental abscesses; temporal from middle ear infections; cerebellar from chronic mastoidosis.
histologic features of bacterial brain abscesses
begins as cerebritis with neurophils and capillary dilation
then progresses to central necroses with macrophages and surrounding edema. also see reactive astrocytes. eventually, see encapsulation by granulation tissue. may be dangerous due to surrounding edema.
Whipple’s disease
due to gram-pos bacteria called Tropheryma Whipple. this is a systemic disease that usually involves the bowel and mesenteric lymph nodes. brain may occuasionally be only organ affected. may see dementia, facial myoclonus, supranuclear palsy, visual impairment, seizures. see foamy macrophages with intensely PAS positive, diatase riesistanc bacilliform bodies.
actinomycosis and nocardiosis
due to paracranial lesions or are blood-borne. see sulfur granules.
