"On T1-weighted images, the signal intensity of clivus varies with age. In childhood, red haematopoetic bone marrow contributes to low signal intensity on T1-weighted images. As the child ages, the signal intensity of clivus becomes heterogenous with increasing infiltration of fatty marrow and subsequently become hyperintense in old age 5."
"There are multiple variant defects or channels through the clivus 4:"
"There are several occipital vertebrae variants in which bony protuberances arise from the clivus at the anterior margin of the foramen magnum 4:"