EMmedonline

There are five major brain herniation syndromes

• Subfalcine or cingulate herniation

• Uncal herniation

• Transtentorial herniation

• Cerebellotonsillar herniation

• Upward posterior fossa

Subfalciane herniation

• It is the most common cerebral herniation pattern, characterized by displacement of the brain beneath the free edge of the falx cerebri due to raised ICP.

• It can compress the ipsilateral anterior cerebral artery and lead to contralateral weakness.

Uncal Herniation

• It is the most commonest.

• It occurs when the uncus of the temporal lobe is displaced inferiorly through the medial edge of tentorium.

• Uncal transtentorial herniation leads to compression of parasympathetic fibers running with third cranial nerve, causing an ipsilateral fixed and dilated pupil due to unopposed sympathetic tone.

• Further herniation compresses the pyramidal tract, which results in contralateral motor paralysis.

Brain Herniation Types : 1 :Uncal Herniation ; 2 :Central Transtentorial Herniation 3 : Subfalcine Herniation; 4 :Transcalvarial Herniation; 5 : Upward Transtentorial Heniration 6:Tonsillar henrniation. 

Attribute : "Brain herniation types-2" by Brain_herniation_types.svg: User:Delldotderivative work: RupertMillard (talk) - Brain_herniation_types.svg. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Brain_herniation_types-2.svg#mediaviewer/File:Brain_herniation_types-2.svg

Central Transtentorial Herniation

• It is less common.

• It occurs in the midline lesions in the frontal or occipital lobes or in the vertex.

• Most prominent symptoms are initial bilateral pinpoint pupils, bilateral babinski's sign and increased muscle tone.

• Fixed midpoint pupils follow along with prolonged hyperventilation and decorticate posturing.

Cerebellotonsillar herniation

• Cerebellotonsillar herniation occurs when cerebellar tonsils herniate through foramen magnum.

• This leads to pinpoint pupils, flaccid paralysis and sudden death.

Upward Transtentorial Herniation

• Results from a posterior fossa lesion and leads to a conjugate downward gaze with absence of vertical eye movements and pin point pupils.

A Plain CT film of brain of 70 year old man presented with fever since 3 days with sudden onset of alterted sensorium with drop in GCS. On subsequent imaging revealed upward transtentorial herniation probably secondary to brainstem encephalitis.

Management of Raised ICP

• Drain CSF via ventriculostomy ; Maintain ICP < 20mmHg and CPP >60 mmHg

• Elevate head of the bed; midline head position.

• Osmotherapy- mannitol 25 – 100gm Q 4h as needed (Serum osmalility < 320 mosmol) / Hypertonic saline

• Glucocorticoids : Dexmathasone 4mg q6h for vasogenic edema from tumor, abscess (Avoid glucocorticoids in head trauma, ischemic and hemorrhagic stroke).

• Sedation (Eg : morphine, propofol or midazolam); add neuromuscular paralysis if necessary (Patients who is mechanically ventilated).

• Hyperventilation : Paco2 30 -35 mmHg

• Pressor therapy : Phenylephrine, dopamine or norepinephrine to maintain adequate MAP to ensure CPP >60 mmHg.

• Consider second tier therapies for refractory elevated ICP

• High dose barbiturate therapy

• Aggressive hyperventilation

• Hypothermia

• Hemicraniectomy

Updated on  : 9/1/15

Reference

• Tintinalli
• Harrison 18th edition