Ependymitis granularis sounds far more worrying than it actually is. The term refers 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 have a triangular morphology extending laterally from the callosal genu. Pathologic lesions tend to be larger and demonstrate corresponding low signal intensity in T1WI.
Three findings contribute to the appearance 1:
- decreased myelin
- focal breakdown of the ependymal lining and astrocytic gliosis (true ependymitis granularis)
- 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.
- 1. Sze G, De armond SJ, Brant-zawadzki M et-al. Foci of MRI signal (pseudo lesions) anterior to the frontal horns: histologic correlations of a normal finding. AJR Am J Roentgenol. 1986;147 (2): 331-7. AJR Am J Roentgenol (abstract) - Pubmed citation
- 2. Nelson, Sarah H. A case of chronic internal hydrocephalus due to ependymitis granularis the journal of neurology and psychopathology. s1-7 (26): 117. doi:10.1136/jnnp.s1-7.26.117