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Uncal herniation carries a bad prognosis due to the direct compression of the vital midbrain centers. midbrain effaced and displaced inferiorly.complete obliteration of suprasellar cistern.both temporal lobes herniated into tentorial incisura.occurs due to extensive mass effect or severe trauma, less common.inferomedial displacement of posterior communicating and posterior cerebral arteries.

asymmetrical inferior midbrain displacement and effacement.widening of cerebellopontine angle (ipsilateral).mass effect and obliteration of the suprasellar cistern (ipsilateral).medial displacement of the temporal horn of the lateral ventricle.medial displacement of the uncus and parahippocampal gyrus of the temporal lobe.Uncal herniation can be suggested on CT, however, MRI is the gold standard.įeatures of unilateral descending tentorial herniation include: Uncal herniation occurs secondary to large mass effect (that can occur from traumatic or non-traumatic hemorrhage, malignancy, etc.) that will lead to increased intracranial pressure and herniation. In uncal herniation, the uncus and the adjacent part of the temporal lobe glide downward across the tentorial incisura compressing the brainstem and the posterior cerebral arteries in the ambient cistern. Uncal herniation may be unilateral or bilateral 1,2. in ~25% ipsilateral hemiparesis due to Kernohan phenomenon.compression of the reticular activating system of the mesencephalon leads to alteration in conscious state.vertical gaze palsy may occur after compression of the rostral interstitial nucleus of the medial longitudinal fasciculus.ptosis may occur due to oculomotor nerve palsy (not paralysis of Müller's muscle).tonic lateral deviation may occur due to unopposed abducens nerve activity.rarely, an isolated contralateral dilated pupil that is unresponsive to light may develop, signifying contralateral oculomotor nerve compression from midline shift.may develop into bilaterally blown pupils due to compression of the mesencephalon and its parasympathetic nuclei.initially, an ipsilateral dilated pupil that is unresponsive to light, signifying ipsilateral oculomotor nerve compression.