What is a Closed Head Injury (CHI)?
A closed head injury includes the various types of injuries that occur within the intact skull. Most are associated with hemorrhages ranging from very small to very large. These hemorrhages are associated with various degrees of brain swelling (cerebral edema). Some CHI may not have hemorrhage, but present with significant brain swelling. The various evolutionary effects from these injuries have a dramatic range from coma and vegetative state to good recovery. With the skull being a closed space, there is little room for the brain to swell. Sometimes an Intracranial Pressure Monitor (ICP Monitor) is placed into the fluid part of the brain (Ventricle) to measure the intracranial pressure to aid in treatment. These monitors also allow drainage of cerebral spinal fluid to give the brain more room to try to accomodate the brain swelling. A large portion of the skull may be surgically removed to give additional room for brain swelling. Some examples of CHI are discussed below.
The image shows the brain with tiny hemorrhages in the left frontal lobe. A cerebral contusion is like a bruise on your brain. Just as you get a "black and blue" mark on your arm from some trauma, you can bruise your brain. In the brain a contusion consists of a mosaic of "good brain" mixed with "bad bran" or "normal brain" mixed with "injured brain". Many times contusions cause the surrounding brain to swell resulting in severe consequences. These hemorrhages are usually small initially (petechial hemorrhages). These small hemorrhages may all coalesce and evolve into a distinct, larger blood clot associated with significant brain swelling (cerebral edema).
Epidural Hematoma (EDH)
When a hemorrhage occurs from lacerating a blood vessel along the dura (membrane covering the brain), the bleeding causes a blood clot between the dura and the skull. This pushes the brain inward resulting in brain swelling (cerebral edema).
Subdural Hematoma (SDH)
When the brain shifts within the skull during trauma, bridging veins can get stretched and tear. This results in bleeding on the surface of the brain, under the dura forming a subdural hematoma. The blood clot pushes the brain inward resulting in pressure on the brain resulting in brain swelling (cerebral edema). Clinically, patients will become progressively lethargic and may rapidly lapse into a coma with an acute subdural hematoma.
Intracranial Presure Monitor (ICP monitor), hemicraniectomy
The left half of the brain has become swollen from a CHI. The left half of the skull has been removed (an operation called a hemicraniectomy) to allow the brain to expand outside the limits of the skull; an ICP monitor was also placed.