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

A 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.

Brain herniations are the most common side effect of tumors in the brain, including:

• Metastatic brain tumor
• Primary brain tumor

A brain herniation can also be caused by:

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

A brain herniation can occur:

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

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

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

Patients with a brain herniation have irregular heart rhythms and difficulty breathing consistently.

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 placed into the brain to help remove fluid
• Corticosteroids such as dexamethasone, especially if there is a brain tumor
• 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 the blood if bleeding is causing herniation

The outlook varies and depends on where in the brain the herniation occured. Death is possible.

A brain herniation itself often causes 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.

• Brain death
• Permanent and significant neurologic problems

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

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