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Introduction to Brain Infections

By John E. Greenlee, MD, Professor and Executive Vice Chair, Department of Neurology, University of Utah School of Medicine

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Brain infections may manifest as follows:

  • Diffuse infection, resulting in encephalitis, sometimes affecting specific areas on the brain

  • Inflammation of the brain secondary to meningeal infections or parameningeal infections

  • Focal infection (eg, due to a brain abscess or to fungal or parasitic brain infections)

Encephalitis is most commonly due to viruses, such as herpes simplex, herpes zoster, cytomegalovirus, or West Nile virus. HIV infection and prion diseases can also affect the brain diffusely.

Slow virus infections, such as progressive multifocal leukoencephalopathy (caused by the JC virus) or subacute sclerosing panencephalitis (caused by the measles virus) also affect the brain; they are characterized by a long incubation and a prolonged course.

Certain noninfectious disorders can mimic encephalitis. An example is anti-NMDA (N-methyl-d-aspartate) receptor encephalitis, which involves an autoimmune attack on neuronal membrane proteins.

Multifocal brain involvement may also be a manifestation of acute diffuse disseminated encephalomyelitis (a postinfectious syndrome).