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tentorial herniaAn intracranial Gotterdamerung consisting of a cerebral hernia in which there is “displacement of the uncus and medial part of the ipsilateral parahippocampal gyrus through the tentorial opening. The medial part of the temporal lobe pushes towards the midline and over the free edge of the tentorium, narrowing the transverse axis of the midbrain. The aqueduct is compressed and the contralateral cerebral peduncle is pushed against the opposite free edge of the tentorium (Kernohan notch). The third cranial nerve becomes angled over the artery and may itself become haemorrhagic. As the tentorial hernia enlarges, it produces a groove on the upper surface of the adjacent cerebellar hemisphere, which may be accompanied by a wedge-shaped infarction along the line of the groove in the parahippocampal gyrus” Black, Graham, Sudden Death Caused by Intracranial Pathology.
These changes obstruct the posterior cerebral artery, resulting in infarction in the medial occipital cortex, caudal displacement and elongation of the brainstem, with haemorrhage and infarction.
Ipsilateral fixed and dilated pupil due to oculomotor nerve damage, ipsilateral weakness due to contralateral cerebral peduncle compression.