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.