🎯 Pathology

• a life-threatening situation that occurs in response to decompensated raised intracranial pressure

• this results in the displacement and compression of brain tissue through structures within the skull

​

💡 Causes

• idiopathic intracranial hypertension

• mass

  • tumour, abscess, haematoma

• increased CSF

  • hydrocephalus

• increased blood volume

  • venous sinus thrombosis

​

⚡️ Types of brain herniation​

​

Subfalcine

• displacement of the cingulate cortex underneath the falx cerebri

• may impact the anterior cerebral artery

​

Uncal (transtentorial)

• displacement of the uncus under the tentorium cerebelli

• the uncus is found on the medial aspect of the temporal lobe

• this type of herniation compresses:

  • oculomotor nerve leading to a surgical third nerve palsy

    • parasympathetic fibres are affected first (as they are more superficial and more susceptible to compression) before the somatic motor fibres: ipsilateral pupillary dilatation prior to the paralysis of the extraocular muscles

  • midbrain compressing the contralateral cerebral peduncle

    • this causes upper motor neuron symptoms

  • compression of the cerebral aqueduct

    • leading to obstructive hydrocephalus

​

Transcalvarial

• displacement of brain tissue through a defect in the skull

​

Transalar (transphenoidal)

• herniation of brain matter in the middle cranial fossa, associated with the greater wing of the sphenoid bone

• herniation can be ascending or descending

 

Central

• herniation of both temporal lobes through the tentorial notch

 

Tonsillar

• herniation of the cerebellar tonsils through the foramen magnum

  • this is also known as “coning”

• usually due to an infratentorial mass

• this is life-threatening because it causes compression of the medulla which houses the cardiorespiratory centre