Uncal transtentorial herniation, or herniation of the medial temporal lobe: Early herniation leads to ipsilateral blown pupil (secondary to ipsilateral cranial nerve [CN] III compression) and contralateral hemiparesis. Late presentation leads to coma and Kernohan phenomenon (ipsilateral hemiparesis due to contralateral compression against the Kernohan notch and a subsequent misleading contralateral blown pupil).
