View source for Brain herniation syndromes

==Background==
*Brain herniation occurs when increased [[intracranial pressure]] causes brain tissue to shift across rigid dural structures (falx, tentorium) or through the foramen magnum
*Represents a life-threatening neurological emergency requiring immediate recognition and intervention
*Most commonly caused by mass lesions ([[intracranial hemorrhage (main)|intracranial hemorrhage]], [[brain tumor|tumor]], [[brain abscess|abscess]]) or diffuse cerebral edema

==Types==
[[File:Brain herniation.png|thumbnail|Type of brain herniation]]
===Uncal (Lateral Transtentorial)===
*Most common clinically significant herniation pattern
*Medial temporal lobe (uncus) herniates over the tentorial edge
*'''Classic triad:''' ipsilateral blown pupil ([[third nerve palsy]]), contralateral [[weakness|hemiparesis]], decreased consciousness
**Contralateral hemiparesis occurs ~75% of the time (ipsilateral ''Kernohan notch'' phenomenon in ~25%)
*May progress to bilateral fixed dilated pupils and posturing if untreated

===Central Transtentorial===
*Both cerebral hemispheres herniate downward through the tentorium
*Progressive rostral-to-caudal deterioration:
**Early: small reactive pupils, [[Cheyne-Stokes respiration]], increased tone
**Late: midpoint fixed pupils, extensor posturing, loss of brainstem reflexes

===Cerebellotonsillar (Tonsillar)===
*Cerebellar tonsils herniate through foramen magnum → brainstem compression
*Pinpoint pupils
*Sudden [[respiratory failure|respiratory]] and [[shock|cardiovascular collapse]]
*Flaccid [[weakness|quadriplegia]]
*'''Most rapidly fatal''' herniation pattern

===Upward (Ascending) Transtentorial===
*Posterior fossa mass pushes cerebellum upward through tentorial notch
*Pinpoint pupils, downward conjugate gaze
*Obstructive [[hydrocephalus]] may occur

===Subfalcine===
*Cingulate gyrus herniates under the falx cerebri
*May compress anterior cerebral artery → contralateral leg weakness
*Often clinically silent early but may progress to other herniation patterns

==Clinical Features==
*Decreasing [[Glasgow Coma Scale (GCS)|GCS]]
*Unilateral or bilateral pupil dilation and fixation
*Abnormal posturing (decorticate → decerebrate)
*[[Cushing reflex]]: [[hypertension]], [[bradycardia]], irregular respirations (late finding)
*Loss of brainstem reflexes (corneal, gag, oculocephalic)
*Respiratory pattern changes (Cheyne-Stokes → central neurogenic hyperventilation → ataxic → apnea)

==Management==
*'''ABCs''' — secure airway early; avoid hypoxia and hypotension
*'''Elevate head of bed''' 30 degrees, keep head midline
*'''Hyperosmolar therapy:'''
**[[Mannitol]] 1-1.5 g/kg IV bolus
**[[Hypertonic saline]] (23.4%) 30 mL IV over 10-20 min via central line (or 3% saline 250-500 mL via peripheral line)
*'''Hyperventilation''' to PaCO2 30-35 mmHg (temporary bridge — effect lasts 15-20 min)
*Emergent [[neurosurgery]] consult for surgical decompression or EVD placement
*Treat underlying cause (evacuate hematoma, treat [[cerebral edema]])
*Avoid [[hyperthermia]], [[hyperglycemia]], [[seizures]]

==Disposition==
*All patients with brain herniation require emergent ICU admission
*Neurosurgical consultation is mandatory
*Consider emergent operative intervention for:
**Epidural hematoma with herniation signs
**Large subdural hematoma with midline shift
**Obstructive hydrocephalus
*Transfer to neurosurgical center if unavailable on site
*Goals of care discussion appropriate for devastating injuries

==See Also==
*[[Elevated intracranial pressure]]
*[[Head trauma (main)]]
*[[Intracranial hemorrhage (main)]]
*[[Glasgow Coma Scale (GCS)]]

==References==
<references/>

[[Category:Neurology]]