Brain Herniation Flashcards
Brain herniation
Basic structure
Cerebrum: Two Hemispheres: Four lobes
Cerebellum and brainstem
Brain herniation
Basic structure
Meneiges:
Dura mater forms the menigeal folds:
Falx cerebri:
- Down into longitudinal fissure
- Free edge in close contact with corpus callosum
Tentorium:
- Separates cerebrum from cerebellum
- Free edge in close contact with brainstem
Brain herniation
The skull has a set volume and pressure
When there is an impact to the brain = blood starts to pool = mass effect
Brain herniation
Focal mass effect/diffuse mass effect
Depending on where brain herniation occurs can be:
Supratentorium:
- displacement of cerebrum above the tentorium
Infratentorium:
- displacement of cerebellum below the tentorium
Brain herniation
Supratentorial herniations
Uncal herniation (transtentorial)
- Uncus puts pressure on the the occulomotor nerve, giving a an occulomotor nerve palsy
- Eyes usually down and out (loss of innervation of muscles)
- Pupils dilate & fails to constrict in response to light
Brain herniation
Supratentorial herniations
Uncal herniation (transtentorial)
Posterior cerebral artery can also be compressed
- Uncal herniation can also stretch/break branches of the paramedian basilar artery(nourishes brainstem)
- Causes small flame shaped haemorrhages called duret haemorrhages
- Can be seen on an autopsy
Brain herniation
Supratentorial herniations
Uncal herniation (transtentorial)
If there is a mass focal effect on right side of brain, it inc icp and squeezes uncus onto brain stem
- Uncus directly compresses right side of brainstem
- Indirectly pushes left side of brainstem against free edge of tentorium forming a
- Kernohan’s notch
- The compressed part of the brainstem is called the left cerebral peduncle
- This area is rich in nerves that serve the muscles on right side of body
- But eventually injury to left peduncle will cause injury to same side of body to tha of the side of the focal mass effect
- Gives ipsilateral weakness
- Generally damage to brain injury results in damage to contra-lateral side
- Therefore KERNOHAN’S NOTCH causes a false localising sign
Brain herniation
Supratentorial herniations
Central Herniation
Diancephalon and parts of the temporal lobes slip under the free edge of the tentorium
- Diencephalon processes sensory information and emotions
- Also regulates hormone production
- So above processes can be affected
- Dilated and fixed puplis, upward eye movement giving sunset eyes
- Eyeballs downward and part of lower pupils covered by lower lid
- Duret haemorrhages can be seen
Brain herniation
Supratentorial herniations
Cingulate (subfalcine) herniation
The cingulate gyrus gets squeezed blow the free edge of the falx cerebri towards the opposte sid eof the skull
- The displaced part of the brain (after it has been squeezed) compresses the anterior cerebral artery = ischaemic stroke
- Can be a forerunner to other types of supra tentorial herniations
Brain herniation
Supratentorial herniations
Transcalvarial Herniation
(External Herniation)
Brain sueezes out of the skull at a fracture or surgical site
Brain herniation
Infratentorial Herniations
Two types:
Upward/Tonsillar
Upward Herniation:
- Displacement of cerebellum upward through a notch in the tentorium cerebelli
Tonsillar Herniation
- Parts of the cerebellum called cerebellar tonsils slip down through an opening in the skull called the foramen magnum, can affect breathing and cardiac function
- Most common sign is headache and neck stiffness
- Also LOC, flaccid paralysis
Increased Intracranial Pressure
Decreased levels of conciousness
Focal neurological signs
Papilledaemia
- swelling of optic disc, is the point where optic nerve fibres leave retina
Also have inc BP
Irregular breathing
Bradycardia
Above three known as CUSHING’S TRIAD
Lumbar puncture is a relative contraindication in ICP due to possible herniation
Increased Intracranial Pressure
Treatment
- Reduce pressure within the skull
- Treat underlying cause
- External ventricular drain
- Decompressive craniectomy
- Osmotic therapy (mannitol)
Brain Herniation
Summary
