52. Herniation syndromes

Question 1

What is brain herniation?

Answer 1

A potentially life-threatening condition when ICP is increased, leading to a shift of cerebral tissue from its normal location, into an nearby space as a result of mass effect. Herniations can occur, either alone or in combination.

Tentorium cerebelli and falx cerebri (folds):
- A part of the brain compressed by an extrinsic lesion or is expanded by an intrinsic lesion => herniates from one cranial compartment to another.

Question 2

Causes

Answer 2

Factors that cause a mass effect and IC
=> traumatic brain injury
=> IC hemorrhage
=> brain tumor
=> Subdural hematoma
=> abscess
=> cerebral infarction

Any conditions ass. w/increased cerebral edema and increased ICP:
HIE, stroke, meningitis, and hydrocephalus

Lumbar puncture –> tonsillar herniation

Question 3

Classification

Answer 3

Supratentorial herniation (STH)
Infratentorial herniation (ITH)

Question 4

STH subdivisions

Answer 4

Uncal (tentorial)
Central (tentorial)
Cingulate (subfalcine/transfalcine)
Transcalvarial
Tectal (posterior)

Question 5

ITH subdivisions

Answer 5

Tonsillar (downward cerebellar)

Upward (upward cerebellar or upward transtentorial)

Question 6

Consequence

Answer 6

Compress brain parenchyma, ventricles, and cerebral blood vessels.

Question 7

Signs and symptoms

Answer 7

The rate of symptom progression is related to the rate of lesion expansion

Tentorial herniation, lat. (uncal):

• (Pos. cerebral artery) Homonymous hemianopia
• (Reticular formation) Deterioration of conscious level
• (Tentorium cerebelli, Kernohan’s notch) Limb weak., ipsilateral as the lesion
• (CN III & its nucleus compression) Pupil dilatation; fail to react to light; ptosis; impaired eye move

Tentorial herniation, central:

• (Diencephalon, midbrain, diortion & strecthing of perforatin vessels) Detoriation of conscious level; pupil small; dilated & fixed to light
• (Pretectum & sup. colliculi - dorsal) Impair eye move.; % upward gaze
• Can progress to tonsillar
• (Pituitary stalk & hypothalamus) Dia. insipidus

Tonsillar herniation:

• (Foramen magnum) Neck stiffness; head tilt
• (Brainstem) Dep. of conscious level; resp. irreg. –> resp. arrest

Subfalcine herniation:
- (Ant. cerebral arteries) Leg weak.

Question 8

Diagnosis

Answer 8

CT/MRI, ICP monitoring