Last revised by Brian Gilcrease-Garcia on 14 Dec 2018

Cerebritis is a term that represents inflammation of the brain in the setting of infection, before the development of a cerebral abscess

Cerebritis is essentially the same as encephalitis except that it is used to denote brain parenchymal inflammation secondary to infection with bacteria or other non-viral pathogens. In contrast, encephalitis usually is assumed to denote inflammation due to a virus or paraneoplastic/autoimmune process 1

Cerebritis is divided into early and late phases and lasts typically 10-14 days depending on the virulence of the pathogen 3

Early cerebritis is usually a relatively short-lived phenomenon (2-3 days), representing edema, vascular congestion and coagulative necrosis 1,2.

Late cerebritis represents progressive infection, such that areas of the brain undergo liquefactive necrosis. It occurs at approximately 1 week from initial infection. 

Late cerebritis may progress and organize to form a cerebral abscess, where a capsule of granulation tissue lines a cavity containing purulent material 1,2. This may occur approximately 2 weeks from initial infection.

  • early cerebritis
    • may appear normal by CT
    • poorly marginated cortical or subcortical hypodensity with mass effect, corresponding to edema
    • little or absence of enhancement
    • +/- small areas of hemorrhage
  • late cerebritis
    • more defined, but still irregular, rim-enhancing lesion with a hypodense center

MRI is more sensitive to the early changes of cerebritis and will demonstrate the signal changes expected for an area of inflammation 1

  • early cerebritis
    • T1: iso- to hypointense
    • T2/FLAIR: increased signal with surrounding vasogenic edema
    • T1 C+: no or minimal heterogeneous enhancement
    • DWI/ADC: restricted diffusion, may be patchy
  • late cerebritis
    • progressive, especially peripheral, enhancement (not well-defined vs abscess)
    • progressive restricted diffusion

In most cases cerebritis has progressed to cerebral abscess by the time the diagnosis is made; however, if detected early enough, medical management with antibiotics can successfully treat cerebritis 2.

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