[Supravermian subdural triangle limited by the veins of the posterior fossa. Normal radio-anatomical study. Vermis herniation in the supravermian subdural space or superior vermis herniation].

The author describes a conical sub-dural space above the vermis limited in front by Galien's ampulla, behind by the right venous sinuses and, below by the superior cerebellar vein. This space, which is not filled with air injected by the cisternal route, is only shown in lateral views thanks to its venous outlines. In cases of raised intracranial pressure, the superior cerebellar vermis may occupy this space so that a sort of impaction occurs at this level, which the author proposes calling smaller than superior vermial impaction greater than. Among forms of cerebral herniation, vermial impaction may not occur when the CSF obstruction occurs at another level.