CNS Infections Flashcards
What is the #1 route of CNS infection?
hematogenic (travels from somewhere else via blood)
Pathology of Meningitis v Encephalitis v Abscesses
- Meningitis = outer brain coated in pus; blue dots of neutrophils and macrophages in normally clear CSF; also get vascular damage
- Actual brain - encephalitis (“cerebritis”)
- Polioencephalitis = gray matter
- Leukoencephalitis = white matter (axons/myelin)
- Panecphalitis = both gray & white matter; can be necrotizing or non-necrotising
- Abscess = ring enhancing (often directly from sinus or thru blood; can have epidural abscess in SC)
Examples of Viral Etiologies
- Acute - Herpes, Rabies, enteroviruses, arenaviruses
- Chronic - HIV, Measles, JC virus (PML)
- Meningitis - most commonly enterovirus
- Encephalitis - West Nile, Zika
Examples of Bacterial Etiologies
esp in neonates thru vaginal canal (E coli); strep pneumo or neisseria meningititis in kids/adults (H flu vaccine now)
Which 2 bacterial meningitis infections come on slowly/
- Tuberculosis - slow growing; symptoms over 2-3 wks; also occurs at base of brain so see cranial nerve deficits; dec glucose & inc protein in CSF
- Lyme Disease - can spread to meninges @ wks to months after initial infection (meningitis) then stage 3 can turn into encephalopathy
Where does HSV 1 localize in CNS?
localizes to temporal lobes in adults —> personality changes
Where does Rabies localize in CNS?
spreads to limbic system (rage & biting others)
PML
progressive multifocal leukencephalopathy - infection w/ JC virus (almost everyone is infected); causes chronic de-myelinating disease; so white matter but axons spared (just myelin); abnormal astrocytes
Prions (what are they? pathology?)
- non inflammatory neurodegenerative; inherited and infectious; no nucleic acid; may be spread by blood transfusion or organ transplant; accumulation of protease-resistant protein (CJD)
- Pathology = cerebral atrophy & gliosis
Examples of Fungal Etiologies
usually if immunosuppressed; via blood (except mucor via direct extension from frontal sinus); cryptococcus will have capsule (PAS)
Examples of Parasitic Etiologies
amebas (including Naegleria fowleri in fresh water —> cribriform plate —> brain), toxoplasmosis (multiple ring enhancing lesions), malaria (plasmodium likes RBCs —> blood to CNS)
Symptoms of Meningitis v. Encephalitis
- Meningitis - headache, stiff neck, inc pleocytosis in CSF (WBCs)
- Encephalitis - Increased intracranial pressure common ; altered consciousness, focal neurological signs, accentuated tendon reflexes, seizures, tremors; sometimes symptoms related to regional involvement
