Ascending transtentorial herniation [Neurosurgery Wiki]

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====== Ascending transtentorial herniation ======

Occasionally seen with [[posterior fossa lesion]]s, it may be exacerbated by [[ventriculostomy]]. Cerebellar [[vermis]] ascends above [[tentorium]], compressing the [[midbrain]], and possibly occluding [[SCA]]s → cerebellar infarction. May compress [[Sylvian aqueduct]] → hydrocephalus.

[[Transtentorial herniation]] can occur when the brain moves either up or down across the tentorium, called ascending and descending transtentorial herniation respectively; however descending herniation is much more common.

Radiographic features

General imaging features include

Flattening or reversal of the smile shaped [[quadrigeminal cistern]].

Obliteration of the quadrigeminal and superior cerebellar cistern in severe cases
    
"spinning top" appearance of midbrain due to bilateral compression of the posterior aspect of the midbrain     may be associated with infarct in the territory of posterior cerebral and superior cerebellar arteries    hydrocephalus as the result of the pressure of the cerebellum on the cerebral aqueduct



{{::ascendingtranstentorialherniation.jpg|}}

Cranial shift of vermis and parts of superomedial cerebellar hemisphere through tentorium incisura 

Compressed superior cerebellar, vermian cisterns and forth ventricle 

{{spinningtop.jpg}}