Brain Herniation

Overview

Brain herniation happens when something inside the skull, such as bleeding, swelling, or a growing mass, raises the pressure so much that part of the brain is forced out of its normal compartment. The skull is a closed box that cannot expand, so when pressure builds in one area, soft brain tissue gets pushed through the rigid folds of tissue and bony openings that separate the compartments.

This is one of the most serious neurological emergencies. As brain tissue is displaced, it can compress blood vessels and the brainstem, which controls breathing, heart rate, and consciousness. Brain herniation can cause permanent damage or death within minutes to hours, so it requires immediate emergency treatment. Recognizing the early warning signs and getting help quickly can be lifesaving.

Symptoms

Symptoms tend to come on rapidly and worsen quickly. Anyone showing these signs needs emergency care right away.

• Severe, worsening headache
• Drowsiness, confusion, or difficulty staying awake
• Loss of consciousness or coma
• One or both pupils becoming enlarged and not reacting to light
• Weakness, paralysis, or abnormal posturing of the arms and legs
• Vomiting
• Slow or irregular heartbeat and rising blood pressure
• Irregular or stopped breathing
• Seizures

This is a medical emergency. Call emergency services immediately if someone with a head injury, brain bleed, or known brain problem becomes hard to wake, develops an unequal pupil, or stops breathing normally.

Causes

Brain herniation is caused by any condition that raises pressure inside the skull faster than the brain can adjust. Common causes include:

• Bleeding in or around the brain: from severe head injury, a ruptured aneurysm, or a stroke.
• Brain swelling (edema): after major trauma, large strokes, infection, or lack of oxygen.
• Brain tumors: a growing mass takes up space and crowds normal tissue.
• Abscess or infection: a collection of pus or widespread infection such as meningitis or encephalitis.
• Hydrocephalus: a buildup of cerebrospinal fluid that increases pressure.

In each case the underlying problem raises pressure to a point where brain tissue is squeezed past the structures that normally hold it in place.

Risk Factors

The risk of herniation rises with any condition that increases pressure inside the skull. Factors that make it more likely include:

• Severe traumatic brain injury
• Large or rapidly bleeding stroke
• A brain tumor, especially one that grows quickly or bleeds
• Untreated or rapidly progressing hydrocephalus
• Serious brain infections
• Conditions causing severe brain swelling, such as oxygen deprivation or liver failure

Diagnosis

Because herniation is an emergency, diagnosis happens quickly and alongside immediate treatment. Doctors use:

• Neurological examination: checking level of consciousness, pupil reactions, movement, and reflexes to gauge how severe and which type of herniation is occurring.
• CT scan of the head: a fast imaging test that shows bleeding, swelling, masses, and shifting of brain structures.
• MRI: gives more detail when time allows and the patient is stable.
• Intracranial pressure monitoring: a sensor may be placed to measure pressure directly and guide treatment.

Imaging also helps find and target the underlying cause so it can be treated.

Treatment

Treatment aims to lower the pressure inside the skull and fix the cause as fast as possible. This is intensive, hospital-based care.

• Emergency stabilization: securing the airway, supporting breathing, and maintaining blood pressure.
• Medications: drugs such as mannitol or hypertonic saline to draw fluid out of the brain, and sometimes sedatives to lower the brain's demands.
• Draining fluid: a tube may be placed to drain excess cerebrospinal fluid and relieve pressure.
• Surgery: removing a blood clot or tumor, or removing part of the skull (decompressive craniectomy) to give the swollen brain room to expand.
• Treating the cause: controlling bleeding, treating infection, or managing the underlying condition.

The outlook depends heavily on how quickly pressure is relieved and how much damage has already occurred.

Prevention

Herniation itself cannot always be prevented, but the conditions that lead to it can often be managed early. Helpful steps include:

• Wearing helmets and seat belts to reduce serious head injuries
• Getting prompt evaluation for severe or unusual headaches, especially after a head injury
• Following treatment for known conditions such as high blood pressure, tumors, or hydrocephalus
• Seeking immediate care for stroke symptoms or signs of brain infection
• Closely monitoring anyone with a recent serious head injury for worsening symptoms

When to See a Doctor

Brain herniation is a true emergency. Call emergency services immediately if a person has any of the following, particularly after a head injury, stroke, or with a known brain condition:

• Sudden severe headache or rapidly worsening headache
• Becoming confused, very drowsy, or impossible to wake
• One pupil larger than the other or pupils that do not react to light
• New weakness, paralysis, or seizures
• Slow, irregular, or stopped breathing

Do not wait to see if symptoms improve. Every minute matters in preventing permanent brain damage.

Related Topics

Frequently Asked Questions

References

1. National Institute of Neurological Disorders and Stroke (NINDS). Traumatic Brain Injury Information.
2. MedlinePlus, U.S. National Library of Medicine. Brain herniation.
3. Mayo Clinic. Increased intracranial pressure — Symptoms and causes.
4. Centers for Disease Control and Prevention (CDC). Traumatic Brain Injury & Concussion.