Brain herniation Flashcards
(15 cards)
What is brain herniation?
Displacement of brain tissue from one compartment to another due to raised intracranial pressure (ICP), often compressing vital structures and risking death
What are common causes of brain herniation?
Traumatic brain injury
Intracranial hemorrhage
Tumors or abscesses
Cerebral edema
Hydrocephalus
What is subfalcine herniation?
The cingulate gyrus shifts under the falx cerebri (midline shift), potentially compressing the anterior cerebral artery (ACA)
What are clinical signs of subfalcine herniation?
Contralateral leg weakness
Possible ACA infarct
Often first sign of rising ICP
What is uncal herniation?
The uncus of the temporal lobe herniates through the tentorial notch, compressing the midbrain and cranial nerve III
What are clinical features of uncal herniation?
Ipsilateral dilated pupil (CN III palsy) = ptosis, mydriasis, down + out
ipsilateral PCA damage= contralateral homonymous hemianopia w macular sparing
Contralateral hemiparesis UNLESS ITS MASSIVE then causes Kernohan phenomenon which is when the uncal herniation compresses opposite side of brain disturbing corticospinal tract= ipsilateral hemiparesis to the uncal herniation
Reduced consciousness
Can progress to brainstem compression
What is cerebellar tonsillar herniation (coning)?
Downward displacement of cerebellar tonsils through the foramen magnum, compressing the medulla and brainstem.
What are signs of cerebellar tonsillar herniation?
Coma
Respiratory arrest
Brainstem dysfunction or death
What is transcalvarial herniation?
Brain tissue protrudes through a skull defect (e.g. fracture or craniectomy site); visible/palpable external bulge.
Which herniation type involves visible bulging brain tissue through the scalp?
Transcalvarial herniation — occurs through a bony defect in the skull.
What is central herniation?
Downward displacement of diencephalon and brainstem due to diffuse increased ICP; often follows other herniations.
Clinical features of central herniation?
Decreased consciousness
Small reactive → fixed pupils
Bilateral motor weakness
Late: decerebrate posturing
How is brain herniation diagnosed?
CT or MRI brain
Clinical exam (GCS, pupils, motor signs)
ICP monitoring if applicable
How is brain herniation treated?
Osmotic therapy (e.g. mannitol, hypertonic saline)
Hyperventilation (temporary)
Urgent neurosurgical decompression
Treat underlying cause
Phenytoin kinetics + MOA
At therapeutic levels, elimination follows first-order kinetics. In the upper therapeutic and toxic range, elimination changes from first-order to zero-order kinetics due to saturation of the hepatic hydroxylation system
MOA= sodium channel blocker
