Definition

A brain herniation is the displacement of brain tissue, cerebrospinal fluid, and blood vessels outside the compartments in the head that they normally occupy. A herniation can occur through a natural opening at the base of the skull (called the foramen occipitalis) or through surgical openings created by a craniotomy procedure.

Herniation can also occur between compartments inside the skull, such as those separated by a rigid membrane called the "tentorium".

Alternative Names

Herniation syndrome; Transtentorial herniation; Uncal herniation; Subfalcine herniation; Tonsillar herniation; Herniation - brain

Symptoms

• Progressive loss of consciousness
• Coma
• Irregular breathing
• Respiratory arrest (no breathing)
• Irregular pulse
• Cardiac arrest (no pulse)
• Loss of all brainstem reflexes (blink, gag, pupillary reaction to light)

Signs and tests

A neurologic examination would show an impaired level of consciousness. Depending on the severity of the herniation, one or several brainstem reflexes and cranial nerve functions will be impaired. The patient would show an inability to breathe consistently, and heart rhythms would be irregular.

Expectations (prognosis)

Once herniation in the brain's temporal lobe or the cerebellum occurs, death is often inevitable. Herniation of other areas of the brain areas has a more variable outlook.

Complications

• Permanent and significant neurologic problems
• Brain death

Calling your health care provider

If decreased alertness or other symptoms develop suddenly, particularly if there is a known head injury or brain lesion, go to the emergency room or call 911. A neurologist or neurosurgeon will ultimately be involved in the patient's care.

Prevention

Prompt treatment of increased intracranial pressure and related disorders may reduce the risk of brain herniation.

•	Brain surgery
•	Brain tumor - children
•	Metastatic brain tumor
•	Hydrocephalus