Brain herniation is a result of increased intracranial pressure.Types:-1.Cingulate (subfalcine): Pressure is made by falx cerebri. presentation is ischemia due to occlusion of anterior cerebral artery.2.Cerebellar tonsillar: Pressure is by foramen magnum.3A.Downward transtentorial (central): Pressure is by tentorium cerebelli. presentation is compression of CN VI results in diplopia and inability to abduct eye. ischemia occurs due to arterial compromise.3B.Uncal (medial temporal lobe):Pressure is by tentorium cerebelli. presentation is a triad of blown pupil (fixed and dilated) + ptosis (compression of CN III can also result in "down-and-out" eye), ipsilateral hemiplegia (compression of contralateral cerebral peduncle), and coma. Uncal herniation can also result in contralateral homonymous hemianopia which is a result of compression of ipsilateral posterior cerebral artery.