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Brain herniation

Definition

A brain herniation is when brain tissue, cerebrospinal fluid, and blood vessels are moved or pressed away from their usual position inside the skull.

Alternative Names

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

Causes, incidence, and risk factors

Brain herniation occurs when something inside the skull produces pressure that moves brain tissues. This is most often the result of brain swelling from a head injury, stroke, or brain tumor.

Brain herniation is the most common side effect of tumors in the brain, including:

• Metastatic brain tumor
• Primary brain tumor

Herniation of the brain can also be caused by other factors that lead to increased pressure inside the skull, including:

• Abscess
• Hemorrhage
• Hydrocephalus
• Strokes that cause brain swelling

Brain herniation can occur:

• Between areas inside the skull, such as those separated by a rigid membrane like the tentorium or falx
• Through a natural opening at the base of the skull called the foramen magnum
• Through openings created during brain surgery

Symptoms

• Cardiac arrest (no pulse)
• Coma
• Lethargy
• Loss of all brainstem reflexes (blinking, gagging, pupils reacting to light)
• Loss of consciousness
• Respiratory arrest (no breathing)

Signs and tests

Patients with a brain herniation have:

• High blood pressure
• Irregular breathing
• Irregular pulse
• Slow pulse

A brain and nervous system (neurological) exam shows changes in alertness (consciousness). Depending on the severity of the herniation and the part of the brain that is being pressed on, there will be problems with one or more brain-related reflexes and nerve functions.

Treatment

Brain herniation is a medical emergency. The goal of treatment is to save the patient's life.

To help reverse or prevent a brain herniation, the medical team will treat increased swelling and pressure in the brain. Treatment may involve:

• Placing a drain into the brain to help remove fluid
• Corticosteroids, such as dexamethasone, especially if there is a brain tumor, to reduce swelling
• Medications that remove fluid from the body, such as mannitol or other diuretics, which reduce pressure inside the skull
• Placing a tube in the airway (endotracheal intubation) and increasing the breathing rate to reduce the levels of carbon dioxide (CO2) in the blood
• Removing blood or blood clots if they are raising pressure inside the skull and causing herniation

Support Groups

Expectations (prognosis)

The outlook varies and depends on where in the brain the herniation occurrs. Without treatment, death is likely.

A brain herniation often causes a massive stroke. There can be damage to parts of the brain that control breathing and blood flow. This can rapidly lead to death or brain death.

Complications

• Brain death
• Permanent and significant neurologic problems

Calling your health care provider

Call your local emergency number (such as 911) or take the patient to a hospital emergency room if he or she develops decreased alertness or other symptoms, especially if there has been a head injury or if the person has a brain tumor or blood vessel problem.

Prevention

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

References

Cooke JL. Depressed consciousness and coma. In: Marx JA, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2006:chap 14.