The depth-of-fissure sign, also known as apex-of-fissure sign or bottom-of-fissure sign, is a radiographic sign that helps to recognize cerebellar infarcts in children as well as in adults .
The 'depth-of-fissure' sign is recognized on cross-sectional imaging studies of the brain, especially MRI and to a lesser degree CT. The sign is best appreciated in either the sagittal or coronal plane .
The key imaging feature of the depth-of-fissure sign is T2 and FLAIR hyperintensity and T1 hypointensity confined to the gray matter at the depths of the cerebellar fissures, typically with sparing of the subjacent white matter in smaller infarcts. In addition, small infarcts may occur along cerebellar fissures, also with relative sparing of the subjacent white matter .
The imaging sign helps to distinghuish cerebellar infarcts from normal cerebellar fissures and from other focal lesions affecting the cerebellum, such as demyelinating lesions or tumors . Often, multiple depth-of-fissure lesions are seen in the same patient .
CT densities and MRI signal intensities are identical to infarcts in other regions of the brain. Although they may be seen in watershed infarcts in children, the depth-of-fissure sign is most often seen in the aging population. In this population, small cerebellar infarcts often present as an incidental finding in the chronic phase after infarct retraction and cavitation with surrounding gliosis .