Uncal Herniation Syndrome After Severe Head Injuries

Severe head injury can result in extra-axial hematoma, cerebral contusion, or diffuse cerebral edema which, in turn, may cause one of five brain herniation syndromes:

1. uncal, 
2. central
3. transtentorial, 
4. cerebellotonsillar, 
5. subfalcine, and external.

Uncal herniation occurs when the uncus of the temporal lobe is displaced inferiorly through the medial edge of the tentorium.
Compression of cranial nerve III can cause an ipsilateral dilated pupil. Typically, patients with uncal herniation are unconscious and require intubation. A contusion to the eye may also result in a dilated, non responsive pupil and arouse suspicion for severe head injury and uncal herniation
but typically these patients will be alert.

                                         Ipsilateral Dilated Pupil due to Uncal Herniation.
      ( CT revealed an epidural hematoma and unilateral effacement of the quadrigeminal cistern. )

Management: Intubate unconscious head trauma patients with a unilateral dilated pupil and transfer them immediately to a facility capable of caring for traumatic brain injury. A noncontrasted head CT scan can identify a subdural or epidural hematoma, diffuse edema, or temporal lobe contusion. These conditions often cause midline shift of cerebral structures and compression of the quadrigeminal cistern. Unilateral effacement of the quadrigeminal cistern confirms uncal herniation.


Initial management focuses on maintaining cerebral perfusion pressure and normal tissue oxygenation as hypotension and hypoxia significantly contribute to secondary brain injury. Mannitol,
hypertonic saline, burr holes, and hyperventilation should be considered in ED patients with uncal herniation. Definitive care requires neurosurgical consultation.

Important Points: 
1. Uncal herniation is the most common of the five herniation syndromes.
2. If a patient has a unilateral dilated pupil after head and face trauma but is awake and talking, be suspicious for isolated traumatic anisocoria.
3. Steroids have no role in the ED management of traumatic brain injury.
4. A temporal lobe contusion in an initially neurologically intact patient may continue to expand and cause uncal herniation.
5. Excessive hyperventilation (PaCO2 < 25 mm Hg) in patients with severe traumatic brain injury is associated with cerebral ischemia.
6. Effacement of the quadrigeminal cistern is the hallmark CT finding of uncal herniation.