Ependymitis granularis is symmetrical foci of periventricular high T2 and FLAIR signal hyperintensity anterior and lateral to the frontal horns.
They are usually small , less than 1 cm, and have a triangular morphology extending laterally from the callosal genu.
It is thought to occur secondary to either a focal breakdown of the ependymal lining with adjacent astrocytic gliosis; and into this region periependymal CSF/fluid preferentially drains.
Is it important?
Well no. Depite its name giving the sound of something that is inflamatory, and a 1926 article (J Neurol Psychopathol. October; 7 (26):117-124) that claimed it as a cause of chronic internal hydrocephalus, it is just an anatomical variant.