brain, spinal cord, and nerve disorders
Brain Herniation
Introduction
Brain herniation occurs when pressure within the skull (intracranial pressure) is increased, causing the brain to be pushed sideways and downward through small normal openings in the relatively rigid sheets of tissue that divide the brain into compartments. Brain herniation is a medical emergency. Brain herniation may occur when a brain tumor, bleeding in the brain, another mass, or a disorder (such as liver or kidney failure) greatly increases pressure within the skull. Symptoms vary depending on which part of the brain is being compressed and can include abnormal breathing, abnormal muscle contractions, eye problems, impaired mental function, and coma. Computed tomography or magnetic resonance imaging is done to diagnose brain herniation. Doctors treat causes if possible and take measures to support breathing (such as mechanical ventilation) and to reduce the increased pressure within the skull. A large mass, such as a brain tumor, an accumulation of blood (hematoma), or swelling can push the brain against the relatively rigid sheets of tissue that divide the brain in compartments. As a result, brain tissue may be damaged. If pressure is put on the areas of the brain that control consciousness, stupor or coma results. If the pressure is high enough, the brain may be forced through small openings in these dividers. This life-threatening disorder is called Herniation: The Brain Under Pressure . Herniation can further damage brain tissue, making an already dire condition worse. There are two common types of herniation. They are named after the structure that the brain is pushed through: Transtentorial herniation:The upper part of the brain (cerebrum) is forced through the tentorial notch, which divides the cerebrum from the lower parts of the brain (cerebellum and brain stem). In people with this type of herniation, consciousness is reduced. The side of the body opposite the tumor may be paralyzed. The pupil of the eye on the side of the herniation may widen (dilate) and may not narrow (constrict) in response to bright light. Tonsillar herniation:A mass (tumor or bleeding) in the lower part of the brain pushes the lowest part of the cerebellum (cerebellar tonsils) through the opening at the base of the skull (foramen magnum). As a result, the brain stem, which controls breathing, heart rate, and blood pressure, is compressed and malfunctions. Bleeding or swelling in the brain can increase pressure within the skull. The pressure may force the brain sideways and downward in the skull through small openings in the relatively rigid sheets of tissue that separate the brain into compartments. The result is brain herniation. These dividers are extensions of the outer layer of tissue covering the brain (the dura mater.) Herniation compresses brain tissue and thus damages it. Brain herniation results from disorders the can cause pressure within the skull to increase. They include Masses in the brain, such as Intracranial Hematomas , areas of swelling (edema), an accumulation of blood ( Widespread swelling caused by liver or kidney failure Increased pressure in the veins carrying blood away from the brain (such as the jugular veins) Blockages of cerebrospinal fluid (the fluid that flows through the tissues covering the brain and spinal cord and fills the spaces within the brain) Increased pressure in the veins carrying blood from the brain may result from heart failure, blockages in the veins, or venous sinus thrombosis (a blood clot in the large veins that drain blood from the brain). 