| Brain herniation: Occurs secondary to mass effect Subfalcine herniation: most common - cingulate gyrus displaced across midline under the falx cerebri - May compress adjacent lateral ventricle; - May enlarge contralateral ventricle due to obstruction at level of foramen of Monro - Risk of ACA comprssion and infarction in the distribution of the callosomarginal branch of the ACA, where it is trapped against the falx. Uncal herniation: - medial aspect temporal lobe displaced medially over free margin of tentorium - focal effacement ambient cistern and lateral aspect suprasellar cistern - possible PCA compression and infarction - possible compression of CN3 - (results in pupil dilatation) and contralaterla cerebral peduncle (ipsilateral hemiparesis) Transtentorial herniation: - descending transtentorial herniation -- effacement of the suprasellar and perimesencephalic cisterns Ascending transtentorial herniation: uncommon -- Vermis and parts of cerebellar hemispheres herniate upward through tentorial incisura Tonsilar herniation - Cerebral tonsils downwardly displaced through foramen magnum - may compress medulla External heniation: - protrusion of brain parenchyma through a surgical or traumatic skull defect |
Sunday, January 5, 2014
Brain herniation
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"Brain herniation:
ReplyDeleteOccurs secondary to mass effect caused by head trauma, intracranial hemorrhage, infarction or neoplasm
Subfalcine herniation: most common
- cingulate gyrus displaced across midline under the falx cerebri
- May compress adjacent lateral ventricle;
- May enlarge contralateral ventricle due to obstruction at level of foramen of Monro
- Risk of ACA comprssion and infarction in the distribution of the callosomarginal branch of the ACA, where it is trapped against the falx.
Uncal herniation:
- medial aspect temporal lobe displaced medially over free margin of tentorium
- focal effacement ambient cistern and lateral aspect suprasellar cistern
- possible PCA compression and infarction
- possible compression of CN3 - (results in pupil dilatation) and contralaterla cerebral peduncle (ipsilateral hemiparesis)
Transtentorial herniation:
- descending transtentorial herniation
-- effacement of the suprasellar and perimesencephalic cisterns
-- Pineal calcification, usually seen at about the same level as choroid plexus in the trigones of the lateral ventricles, is displaced inferiorly.
Ascending transtentorial herniation: uncommon
-- Vermis and parts of cerebellar hemispheres herniate upward through tentorial incisura
-- caused by large posterior fossa hematoma - can also cause tonsillar herniation through the foramen of Magnum
Tonsilar herniation
- Cerebral tonsils downwardly displaced through foramen magnum
- may compress medulla
External heniation:
- protrusion of brain parenchyma through a surgical or traumatic skull defect"