Head Injury Facts
- Traumatic head injuries are a major cause of death, and disability but it might be best to refer to the damage done as traumatic brain injury.
- The purpose of the head, including the skull and face, is to protect the brain against injury. In addition to the bony protection, the brain is covered in tough fibrous layers called meninges and bathed in fluid that may provide a little shock absorption.
- When an injury occurs, loss of brain function can occur even without visible damage to the head. Force applied to the head may cause the brain to be directly injured or shaken, bouncing against the inner wall of the skull. The trauma can potentially cause bleeding in the spaces surrounding the brain, bruise the brain tissue, or damage the nerve connections within the brain.
- Caring for the victim with a head injury begins with making certain that the ABCs of resuscitation are addressed (airway, breathing, circulation). Many individuals with head injuries are multiple trauma victims and the care of their brain may take place at the same time other injuries are stabilized and treated.
The skull is made up of many bones that form a solid container for the brain. The face is the front part of the head and also helps protect the brain from injury. Depending upon the location of the fracture, there may or may not be a relationship between a fractured skull and underlying brain injury. Of note, a fracture, break, and crack all mean the same thing, that the integrity of the bone has been compromised. One term does not presume a more severe injury than the others. Fractures of the skull are described based on their location, the appearance of the fracture, and whether the bone has been pushed in.
Location is important because some skull bones are thinner and more fragile than others. For example, the temporal bone above the ear is relatively thin and can be more easily broken than the occipital bone at the back of the skull. The middle meningeal artery is located in a groove within the temporal bone. It is susceptible to damage and bleeding if the fracture crosses that groove.
- Basilar skull fractures occur because of blunt trauma and describe a break in the bones at the base of the skull. These are often associated with bleeding around the eyes (raccoon eyes) or behind the ears (Battle's sign). The fracture line may extend into the sinuses of the face and allow bacteria from the nose and mouth to come into contact with the brain, causing a potential infection.
- In infants and young children, whose skull bones have not yet fused together, a skull fracture may cause a diastasis fracture, in which the bone junctions (called suture lines) widen.
- Fractures can be linear (literally a line in the bone) or stellate (a starburst like pattern) and the pattern of the break is associated with the type of force applied to the skull.
- Penetrating skull fractures describe injuries caused by an object entering the brain. This includes gunshot and stab wounds, and impaled objects to the head.
- A depressed skull fracture occurs when a piece of skull is pushed toward the inside of the skull (think of pressing in on a ping pong ball). Depending upon circumstances, surgery may be required to elevate the depressed fragment.
- It is important to know whether the fracture is open or closed (this describes the condition of the skin overlying the broken bone). An open fracture occurs when the skin is torn or lacerated over the fracture site. This increases the risk of infection, especially with a depressed skull fracture in which brain tissue is exposed. In a closed fracture, the skin is not damaged and continues to protect the underlying fracture from contamination from the outside world.
- 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
What May Cause a Head Injury?
Adults suffer head injuries most frequently due to falls, motor vehicle crashes, colliding or being struck by an object, and assaults. Falls and being struck are the most common causes of head injury in children.
Medically Reviewed by a Doctor on 11/8/2016
Patient Comments & Reviews
The eMedicineHealth doctors ask about Head Injury (Brain Injury):