Ependymitis granularis

Last revised by Joshua Yap on 16 Jul 2022

Ependymitis granularis sounds far more worrying than it actually is. The term refers to a histological feature that contributes to symmetrical foci of periventricular high T2 and FLAIR signal hyperintensity anterior and lateral to the frontal horns. It is just an anatomical variant, usually small, less than 1 cm, and has a triangular morphology extending laterally from the callosal genu.

Pathologic lesions tend to be larger and demonstrate corresponding low signal intensity in T1WI.

Pathology

Multiple histological features are thought to contribute to the appearance 1:

  1. focal breakdown of the ependymal lining and astrocytic gliosis (true ependymitis granularis)
  2. decreased myelin 
    • loose and random organization of axons
    • smaller axons than adjacent white matter
  3. increased periependymal and extracellular fluid

Despite the name, which suggests an inflammatory cause, and a 1926 article 2 that claimed it as a cause of chronic internal hydrocephalus, it is just an anatomical variant.

Differential diagnosis

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