Unusually large brain herniation into a giant arachnoid granulation of the left sigmoid sinus.

In the scientific literature, there appears to be an ongoing debate on the clinical significance of these lesions in patients with headaches, epilepsy or intracranial hypertension.

Caution is advised in patients with planned transvenous neurointerventional procedures, and these lesions should not be mistaken for dural venous sinus thrombosis.