The medial tentorium and incisura: normal and pathological anatomy.

There are large variations in the length and breadth of the tentorial incisura, its relationship to the brainstem, and in the exact course and position of the free tentorial margins. On contrast-enhanced CT scans, the obliquely sectioned posterolateral tentorial leaves of the tentorial notch can usually be delineated easily. Lesions intrinsic to the tentorial hiatus are discussed and the CT features of remote mass effects causing transtentorial herniation described.