Intracranial Herniation Syndromes

KEY FACTS

TERMINOLOGY

• Brain displaced from 1 compartment into another

IMAGING

• Subfalcine herniation

○ Cingulate gyrus displaced under falx

○ Lateral ventricle compressed/displaced across midline

○ Contralateral ventricle dilated

• Unilateral descending transtentorial herniation (DTH)

○ Temporal lobe displaced medially into incisura

○ Encroaches on, then effaces suprasellar cistern

• Bilateral DTH ("central herniation")

○ Both temporal lobes herniated into tentorial hiatus

○ Diencephalon crushed against skull base

○ Suprasellar cistern, cerebrospinal fluid spaces obliterated

○ Midbrain/pons displaced inferiorly

• Ascending transtentorial herniation

○ Cerebellum displaced up through incisura

○ Quadrigeminal cistern, tectum flattened

• Tonsillar herniation

○ Tonsils impacted into foramen magnum

○ Cisterna magna obliterated

• Transalar herniation

○ Ascending (middle fossa mass) or descending (frontal

mass)

○ Brain, middle cranial artery herniated up/over sphenoid

• Transdural/transcranial herniation

○ Brain extruded through dural/skull defect

TOP DIFFERENTIAL DIAGNOSES

• Intracranial hypotension

CLINICAL ISSUES

• Uncal herniation: Ipsilateral pupil-involving CN3 palsy,

contralateral hemiparesis

• Progressive bilateral ("central") herniation: Decorticate →

decerebrate → death

(Left) Axial gross pathology

section through the ventricles

in a patient who died of

multiple traumatic injuries

shows findings of severe

subfalcine herniation.

Ventricles are displaced across

the midline, and the cingulate

gyrus ﬈ is herniated under

the falx. Left PCA infarct ﬊

occurred secondary to

descending transtentorial

herniation. (Courtesy R.

Hewlett, MD.) (Right) Axial

NECT in severe trauma shows

subfalcine herniation ſt with

severely compressed left ﬇

and slightly dilated right

lateral ventricle st.

(Left) Submentovertex gross

pathology shows unilateral

descending transtentorial

herniation. Undersurface of

herniated temporal lobe

shows "grooving" ﬈ from

impaction against the

tentorium. Note the 3rd nerve

compression ﬊ and midbrain

displacement. (Courtesy R.

Hewlett, MD.) (Right) Axial

T2WI shows mixed-age

subdural hematomas ﬇

causing typical uncal

herniation. The herniating

uncus ſt, hippocampus st

compress, displace the

midbrain against the opposite

edge of the tentorium ﬊.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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