Temporal encephalocele into transverse sinus in an adult with partial seizures: MRI evaluation of a rare site of brain herniation

Herniation of brain parenchyma outside its normal enclosure (also known as encephalocele) has long been known to occur at certain classic sites and is classified accordingly. With widespread use of modern neuroimaging, the previously unknown atypical and rare sites of encephalocele have now been identified. Brain herniation into a dural venous sinus is one such recently described entity with case reports extending only upto the earlier part of this decade. With no definite clinical symptomatology, imaging is crucial to diagnose this lesion accurately and differentiate it from the more familiar entity in this region of the brain, the arachnoid granulations. Also known as occult encephalocele, focal brain herniation into dural venous sinus has few specific imaging features and characteristic sites. We report a case of a 21-year-old man with partial seizures in whom MRI of the brain revealed focal herniation of the normal temporal lobe parenchyma into the left transverse sinus and discuss the key imaging features and pathophysiology of this entity.