Head Injury (cont.)
More Head Injury Overview
- Intracranial (intra=within + cranium=skull) describes any bleeding within the skull. Intracerebral bleeding describes bleeding within the brain itself. More specific descriptions are used based upon where the blood is located.
- Bleeding in the skull may or may not be associated with a skull fracture. An intact skull is no guarantee that there is not underlying bleeding, or hemorrhage, in the brain or its surrounding spaces. For that reason, plain X-rays of the skull are not routinely performed.
- Epidural, subdural, and subarachnoid bleeding are terms that describe bleeding in the spaces between the meninges, the fibrous layered coverings of the brain. Sometimes, the terms hemorrhage (bleeding) andhematoma (blood clot) are interchanged. Because the skull is a solid box, any blood that accumulates within the skull can increase the pressure within it and compress the brain. Moreover, blood is irritating and can cause edema or swelling as excess fluid leaks from the surrounding blood vessels. This is no different than the swelling that can occur surrounding a bruise on an arm or leg. The only difference is that there is no room within the skull to accommodate that swelling.
- When force is applied to the head, bridging veins that cross through the subdural space (sub=beneath +dura= one of the meninges that line the brain) can tear and bleed. The resultant blood clot increases pressure on the brain tissue. Subdural hematomas can occur at the site of trauma, or may occur on the opposite side of the injury (contracoup: contra=opposite + coup=hit) when the brain accelerates toward the opposite side of the skull and crushes or bounces against the opposite side.
- Chronic subdural hematoma may occur in patients who have had atrophy (shrinkage) of their brain tissue. These include the elderly and chronic alcoholics. The subdural space increases and the bridging veins get stretched as they cross a much wider distance. Minor or unnoticed injuries can lead to some bleeding, but because there is enough space in the skull to accommodate the blood, there may be minimal initial symptoms. Asymptomatic (producing no symptoms) chronic subdural hematomas may be left to resolve on their own; however, it may require attention if the individual's mental status changes or further bleeding occurs.
- Depending upon the neurologic status of the affected individual, surgery may be required.
- Thee dura is one of the meninges or lining membranes that covers the brain. It attaches at the suture lines where the bones come together. If the head trauma is epidural (epi=outside +dura) the blood is trapped in a small area and cause a hematoma or blood clot to form. Pressure can increase quickly within the epidural space, pushing the clot up against the brain and causing significant damage.
- While individuals who sustain small epidural hematomas may be observed, most require surgery. Patients have improved survival and brain function recovery if the operation to remove the hematoma and relieve pressure on the brain occurs before they have lost consciousness and become comatose.
- An epidural hematoma may often occur with trauma to the temporal bone located on the side of the head above the ear. Aside from the fact that the temporal bone is thinner than the other skull bones (frontal, parietal, occipital), it is also the location of the middle meningeal artery that runs just beneath the bone. Fracture of the temporal bone is associated with tearing of this artery and may lead to an epidural hematoma.
- In a subarachnoid hemorrhage, blood accumulates in the space beneath the inner arachnoid layer of the meninges. The injury is often associated with an intracerebral bleed (see below). This is also the space where cerebral spinal fluid (CSF) flows and affected individuals can develop severeheadache, nausea, vomiting, and a stiff neck because the blood causes significant irritation to this meningeal layer. It is the same response that can be seen in patients who have a leaking cerebral aneurysm or meningitis. Treatment is often observation and controlling the symptoms.
Intraparenchymal Hemorrhage/Intracerebral Hemorrhage/Cerebral Contusion
- These terms describe bleeding within the brain tissue itself and can be considered a bruise to the brain tissue.
- Aside from the direct damage to the brain tissue that was injured, swelling or edema is the major complication of an intracerebral bleed.
- Surgery is not often considered except in situations in which the pressure within the skull increases to the point at which part of the bone is temporarily removed to allow the brain to expand. When and if the brain swelling resolves, another operation replaces the piece of skull that was removed.
Diffuse Axonal Injury or Shear Injury
- A potentially devastating brain injury occurs when the brain injury occurs to the axons, the part of the neurons or brain cell that allows those cells to send messages to each other. Because of the damage of electrical flow between cells, the affected individual often appears comatose with no evidence of bleeding within the brain. The mechanism of injury is usually acceleration-deceleration, and the nerve endings that connect the brain cells rip apart.
- Treatment is supportive, meaning that there is no surgery or other treatment presently available. The patient's basic needs are met hoping that the brain will recover on its own. Most don't.
- Concussions may be potentially considered a milder form of this type of injury.
Picture of the areas of the brain subject to injury
Picture of an epidural, subdural, and intracerebral hematomas
Medically Reviewed by a Doctor on 6/4/2014
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