CNS Infections Flashcards
Acute pyogenic meningitis
o Generally reaches the brain by hematogenous spread; subarachnoid
o Neonates - Escherichia coli, group B streptococci
o Infants & children - Streptococcus pneumoniae
o Adolescents & young adults (mini-epidemics, e.g. military recruits) - Neisseria meningitidis
o Elderly - Streptococcus pneumoniae, Listeria monocytogenes
o Inflammatory process tends to cause the brain destruction, not the organism itself
o Symptoms –> headache, photophobia, irritability, clouding of consciousness, neck stiffness
o CSF = cloudy/purulent, increased pressure, increased neutrophils, increasedprotein, decreased glucose
Brain abscess
Predisposing conditions:
- bacterial endocarditis
- cyanotic congenital heart disease = left to right shunt allows passage of clots
- chronic pulmonary sepsis
Primary causative organisms = strep + staph
Patients present with focal deficits + increased ICP
Treatment = surgery + antibiotics
Pathology –> lesions are discrete with central pus and debris surrounded by a hyperemic margin
- If older –> surrounded by a fibrous collagen capsule + edema
Subdural empyema
Epidural abscess
Subdural empyema –> usually caused by spread of infection from the skull or sinuses
Epidural abscess –> occurs in association with osteomyelitis
- usually occurs in spinal cord –> can compress spinal cord
Mycobacteria in the CNS
o TB meningitis –> classically basilar
o Tuberculoma can also occur
o Potts disease –> vertebral TB osteomyelitis with fracture
Neurosyphillis
o Meningovascular neurosyphilis –> chronic meningitis with obliterative endarteritis and a perivascular plasma cell infiltrate
o Parenchymatous
- -> General paresis of the insane = invasion of the brain by treponemal organisms with brain atrophy and resultant severe dementia
- -> Tabes dorsalis =damage to dorsal root sensory nerves with impaired sensation and absence of deep tendon reflexes
Viral meningoencephalitis
Parenchymal infection of the brain associated with meningeal inflammation
General histologic features of viral infections
- Perivascular and parenchymal mononuclear cell infiltrates
- Microglial nodules
- Neuronophagia
- Sometimes viral inclusions
Arthropod borne viral encephalitis
Responsible for most outbreaks of epidemic viral encephalitis
o Eastern, Western, and Venezuelan equine, Japanese B, California, Murray Valley, and tick borne encephalitis
o Animal hosts and mosquito or tick vectors
o Generalized or focal neurological deficits
HSV
o HSV1 = hemorrhagic encephalitis involving the temporal lobes and orbital gyri of the frontal lobes
–> Most common cause of sporadic encephalitis in immune competent hosts
o HSV2 = severe generalized encephalitis in neonates and immunocompromised patients
CMV
Infections occur in fetuses and immunocompromised patients
o Periventricular necrosis and calcification
o Prominent cytomegalic cells with intranuclear and intracytoplasmic inclusions
Poliomyelitis
o Poliovirus = enterovirus that has been controlled by immunization
o Infects lower motor neurons producing a flaccid paralysis with muscle wasting and hypreflexia
o Post-polio syndrome = late neurologic syndrome characterized by progressive weakness associated with decreased muscle bulk and pain
HIV
o Aseptic meningitis
o Meningoencephalitis –> primary infection; microglial nodules containing multinucleated microglia
o Vacuolar myelopathy –> myelin damage
o Cranial and peripheral neuropathies
o Myopathies –> inflammatory and drug related
o Opportunistic infections
Progressive multifocal leukoencephalopahty
Infection of oligodendrocytes by the JC polyomavirus
o Immunocompetent hosts
o “moth eaten” appearance by gross or whole mount pathology
Microscopically
- demyelination with enlarged, “ground glass” oligodendrocyte nuclei (viral accumulation)
- atypical astrocytes that may resemble neoplastic cells
Subacute sclerosing panencephalitis
Presents as a neurodegenerative disease of childhood, caused by mutant measles virus; extremely rare
o Gray and white matter disease (hence the name panencephalitis)
o Nuclear and cytoplasmic viral inclusions
Rabies
Transmitted by the bite of an animal, virus enters CNS by ascending along the peripheral nerves from the wound site; death results from respiratory center failure
o Negri bodies = cytoplasmic eosinophilic inclusions in pyramidal neurons of the hippocampus and cerebellar purkinjie cells
o Rabies viruses are bullet shaped by EM
Fungal infections
Encountered primarily in immunocompromised patients
o Usually result from hematogenous dissemination from a primary infection elsewhere
Patterns vary with organism
o Cryptococcus = meningitis
o Aspergillus + mucormycosis = angioinvasion with hemorrhagic infarcts
o Candida = multiple microabscesses
