Brain Herniation Syndromes
When pressure forces brain tissue out of its normal position
Quick Facts
- Type: Neurological emergency
- Cause: Rising pressure inside the skull
- Triggers: Bleeding, swelling, tumors, severe injury
- Urgency: Life-threatening — call emergency services
Overview
Brain herniation syndromes are serious, life-threatening conditions in which increased pressure inside the skull pushes brain tissue out of its normal position. The skull is a closed, rigid space, so when something inside it takes up extra room, such as bleeding, swelling, or a tumor, pressure rises and can force part of the brain to shift across or through the rigid structures that separate brain compartments.
This shifting can compress vital areas of the brain, including those that control breathing and consciousness, and can quickly become fatal without rapid treatment. Brain herniation is a medical emergency. Call emergency services immediately for sudden severe neurological symptoms. Fast recognition and treatment offer the best chance of survival.
The brain sits within several compartments inside the skull, separated by rigid sheets of tissue and openings through which it connects to the spinal cord. When pressure builds unevenly, brain tissue can be pushed from a higher-pressure area into a lower-pressure one through these gaps. As it shifts, it can pinch blood vessels and press on the brainstem, the area that controls breathing, heartbeat, and consciousness. This is why herniation can deteriorate so rapidly and why it is always treated as a true emergency.
Symptoms
Symptoms reflect rising pressure and pressure on critical brain areas, and can worsen rapidly:
- Severe headache
- Decreasing alertness, drowsiness, or loss of consciousness
- One or both pupils becoming enlarged or unresponsive to light
- Weakness or paralysis, often on one side
- Vomiting
- Abnormal breathing patterns
- Seizures
These are emergency signs. Sudden worsening of consciousness, a blown (enlarged) pupil, or new severe weakness after a head injury or known brain problem requires immediate emergency care.
Causes
Herniation results from anything that raises pressure inside the skull or takes up space within it, including:
- Bleeding in or around the brain: From trauma, a ruptured blood vessel, or stroke.
- Brain swelling: After a severe head injury, large stroke, or lack of oxygen.
- Brain tumors: Including swelling around them.
- Infection or abscess: Causing swelling and pressure.
- Buildup of fluid (hydrocephalus): When normal drainage is blocked.
Risk Factors
- Severe head injury
- Large or bleeding stroke
- Brain tumor or abscess
- Brain infection such as meningitis or encephalitis
- Bleeding disorders or use of blood thinners
- Conditions that cause fluid buildup in the brain
Diagnosis
Diagnosis is urgent and based on clinical signs and imaging:
- Neurological assessment: Checking level of consciousness, pupils, and movement, often using standardized scoring.
- CT scan: A rapid test that shows bleeding, swelling, shifting of brain structures, and the likely cause.
- MRI: May provide more detail when time allows.
- Pressure monitoring: In some critically ill patients, a device measures pressure inside the skull.
Treatment
Treatment is an emergency aimed at quickly lowering pressure and treating the cause:
- Stabilizing breathing and circulation: Including support for the airway.
- Measures to reduce pressure: Such as medications that decrease brain swelling, positioning, and careful control of breathing.
- Draining fluid or blood: Removing excess fluid or a blood clot to relieve pressure.
- Surgery: Including procedures to remove a clot, tumor, or part of the skull to give the brain room.
- Treating the cause: Such as the underlying bleed, infection, or tumor.
Care takes place in a hospital, usually in an intensive care setting.
Prevention
Herniation is prevented by promptly recognizing and treating conditions that raise pressure inside the skull:
- Seeking immediate care for serious head injuries
- Treating strokes, brain infections, and tumors promptly
- Monitoring people at risk closely in the hospital
- Managing blood thinners carefully and treating bleeding disorders
- Wearing helmets and seat belts to reduce head injuries
When to See a Doctor
Brain herniation is a medical emergency. Call emergency services immediately if a person has, especially after a head injury or with a known brain problem:
- Sudden severe headache with vomiting
- Decreasing alertness, confusion, or loss of consciousness
- An enlarged pupil or pupils that do not react to light
- Sudden weakness, paralysis, or seizures
- Abnormal or irregular breathing
Do not wait. Rapid treatment offers the best chance of survival and recovery.
Frequently Asked Questions
What is brain herniation?
Brain herniation occurs when increased pressure inside the skull forces brain tissue out of its normal position. Because the skull is a closed space, swelling, bleeding, or a tumor can push parts of the brain against or through rigid structures, compressing vital areas. It is a life-threatening emergency.
What causes brain herniation?
Common causes include bleeding in or around the brain, severe swelling after injury or a large stroke, brain tumors, infections or abscesses, and a buildup of fluid in the brain. Anything that raises pressure inside the skull can lead to herniation.
What are the warning signs?
Warning signs include a severe headache, decreasing alertness or loss of consciousness, an enlarged pupil that does not react to light, sudden weakness or paralysis, vomiting, seizures, and abnormal breathing. These require immediate emergency care.
How is brain herniation treated?
Treatment is an emergency aimed at quickly lowering pressure and treating the cause. It may include support for breathing, medications to reduce swelling, draining fluid or blood, and surgery such as removing a clot or part of the skull. Care takes place in an intensive care setting.
Can brain herniation be prevented?
It can often be prevented by promptly recognizing and treating conditions that raise pressure inside the skull, such as head injuries, strokes, infections, and tumors. Wearing helmets and seat belts to avoid head injuries and managing blood thinners carefully also help reduce risk.
References
- MedlinePlus, U.S. National Library of Medicine. Brain herniation.
- National Institute of Neurological Disorders and Stroke (NINDS). Traumatic Brain Injury.
- Mayo Clinic. Increased intracranial pressure.
- American Association of Neurological Surgeons (AANS). Brain Herniation.