on 30.1.09 with 0 comments

  • Can be viral, bacterial, fungal, or parasitic

  • If there are abscesses it’s usually due to bacteria

  • Viral encephalitis

    • CMV and herpes are the 2 most common causes

    • Arboviruses (arthropod borne) can also cause encephalitis

      • Transmitted by biting insects

      • Local outbreaks associated with mosquitoes (birds are reservoirs)

      • Viruses: St. Louis, Eastern equine, Western equine, Venezualan equine, California, Japanese, and West Nile virus

    • Mumps, measles, rubella, and chickenpox can cause encephalitis

    • Herpes encephalitis

      • Most common cause of viral encephalitis

      • HSV-1 causes an acute encephalitis that usually involves the temporal lobes

      • HSV-2 is a problem in babies born to infected moms; can cause meningitis in older persons

      • Can occur without active infection elsewhere

    • CMV

      • Seen in the immunocompromised and fetuses

      • Starts as ependymitis and spreads through the CSF

      • Can cause focal, necrotizing lesions of brain tissue that may lead to periventricular calcification

      • Also causes meningitis and spinal radiculitis

    • Poliomyelitis

      • An enterovirus that secondarily involves nervous tissue

      • Initially a meningitis

      • Involvement of only anterior horn motor neurons; produces a flaccid paralysis (death by respiratory paralysis or myocarditis)

      • Pretty much gone now due to vaccine

    • Rabies

      • If untreated, causes a fulminant encephalitis that is always fatal

      • M/O get to CNS by peripheral nerves

      • See local paresthesias at site of wound and malaise, H/A, and F (classic)

      • Selectively involves basal cerebral nuclei, midbrain, and floor of 4th ventricle

      • Negri bodies: intracytoplasmic inclusions of virion aggregates

      • 2 forms

        • Furious: volatile, violent, emotional behavior with lucid states and hydrophobia; usually die from arrhythmias

        • Paralytic (dumb): ascending flaccid paralysis; die of respiratory arrest

    • Subacute sclerosing panencephalitis

      • Kids and young adults who had measles

      • Personality change followed by involuntary movements; progressive over years

      • Defective viral particles lack M protein of viral coat and spread more slowly

Category: Pathology Notes



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