Types of Brain Injury

A list and explanation of types of Brain Injury, from common brain injuries, such as concussions, to less common and more serious brain injuries, such as Anoxic Brain Injury, Hypoxic Brain Injury, Shaken Baby Syndrome, and Hematomas.

Anoxic Brain Injury · Hypoxic Brain Injury · Concussions · Contusions · Coup-Contrecoup Brain Injury · Hematomas · Penetration Injuries · Second Impact Syndrome · Skull Fractures · Brain Swelling · Brain Tearing · Shaken Baby Syndrome

Anoxic Brain Injury

Anoxic Brain Injury is a form of acquired brain injury that occurs when the brain fails to receive oxygen for several minutes or longer. Cells in the brain require oxygen carried by the blood, in order to survive and function properly. Brain cells begin to die after approximately four minutes without oxygen. Anoxic Brain Injury can be divided into three types:

Anoxic Anoxia : The brain is injured because no oxygen is supplied; may be caused by extreme altitudes. Toxic Anoxia: The brain is injured because toxins prevent the brain from using oxygen. Anemic Anoxia: The brain is injured because the blood does not carry enough oxygen.

Anoxic brain injury may occur due to drowning, choking, suffocation, electrical shock, or some respiratory difficulty. Recovery from anoxic brain damage can be uncertain and can take an extended period of time. A person’s chance for recovery depends on the extent of the brain damage and the part of the brain involved.

Hypoxic Brain Injury

Hypoxic Brain Injury is a type of acquired brain injury that occurs when the brain's supply of oxygen is dramatically reduced. It differs from anoxic brain injury because anoxia means there is no oxygen going to the brain. However, this does not mean that a hypoxic brain injury is any less serious. Mild cases of Hypoxic Brain Injury may result in memory loss, symptoms of amnesia, difficulty concentrating, and impairment of motor skills. More severe cases may be characterized by unconsciousness and total unresponsiveness to any stimuli; brain death may follow. Hypoxic Brain Injury can be caused by a number of circumstances, including carbon monoxide poisoning, cyanide poisoning, heart attack, shock, asphyxiation, and paralysis of respiration.

Concussions

A concussion is the most common type of traumatic brain injury and often occurs after a blow to the head. In most cases, the brain does not suffer any actual structural damage, but blood vessels may be stretched and some cranial nerves may be damaged. A concussion can range in severity from mild to severe and may be followed by brief unconsciousness, memory loss, loss of balance, depression, and difficulty concentrating.

Concussions are common in contact sports and car accidents. Depending on the severity of the concussion, post-concussion symptoms may last up to a few weeks. Complete recovery may occur in a few months, but in some cases it can take several years. People who have had a concussions in the past are at a higher risk for having concussions in the future.

The American Academy of Neurology has set the following guidelines for grading concussions:

Grade I is characterized by confusion without amnesia, with symptoms lasting less than 15 minutes and no loss of consciousness. Grade II is characterized by confusion with amnesia, with symptoms lasting more than 15 minutes and no loss of consciousness Grade III is characterized by any loss of consciousness. In the case of a Grade III concussion, the individual should be transported to a hospital immediately.

Contusions

A contusion is a bruise, or internal bleeding, occurring on the brain, and is also known as cerebral contusion. The bruise forms when a trauma to the head causes microhemorrhages, which are blood vessels leaking into brain tissue. A contusion differs from a concussion, but a person may have a concussion and a contusion at the same time. Contusions are often more serious than concussions. A person with a contusion may exhibit symptoms including unconsciousness, lack of motor coordination, numbness, memory loss, and cognitive problems. The severity of a brain contusion depends on where the injury occrs and the amount of bleeding and hemorrhage that result. The hemorrhages resulting from a contusion may increase intracranial pressure, causing further complications by forcing the delicate brain tissue against the rough inside of the skull.

Coup-Contrecoup Brain Injury

In a Coup-Contrecoup brain injury, there are two contusions: one at the site of the head trauma and the other on the opposite side of the brain. The coup injury occurs when the head is stopped suddenly and the brain rushes forward. The brain is injured when it hits the side of the skull and as it rubs against the skull's inner ridges, causing the first contusion. The countrecoup injury occurs when the brain bounces off the primary impact surface and collides with the opposite side of the skull, causing the second contusion. Coup countrecoup injuries can occur in motor vehicle accidents, and often result in severe cognitive and psychological deficits.

Hematomas

A hematoma is a collection of blood resulting from internal bleeding. A subdural hematoma (SDH) is a type of traumatic brain injury that occurs when blood collects on the surface of the brain. SDH is caused by tears in the tiny veins between the surface of the brain and its outer covering (the dura). Subdural hematomas may result from traumas to the head or from an aneurysm (the spontaneous rupturing of a blood vessel in the brain). Old age, young age, use of blood thinners, and long term alcohol abuse are among the risk factors for SDH. SDH can be diagnosed by MRI or CAT scan.

Subdural hematomas can be categorized as acute, subacute, or chronic, depending on the speed of onset. Acute subdural hematomas usually result from head trauma and have a high mortality rate if they are not rapidly treated with surgical decompression. One of the dangers of hematomas is an increase in intracranial pressure (ICP). This can force the delicate tissue of the brain against the rough inside of the skull, causing pain and damage. The pressure may result in the slurring of speech, difficulty walking, or dizziness. If not treated quickly and correctly, it can lead to a coma or death.

Penetration Injuries

A Penetration Brain Injury is one in which damage is caused by an object that enters the brain. The damage is caused by the impact of the object itself, as well as by forcing bits of skin, hair, bone, and fragments of the object into the brain. The penetrating object can by a knife, bullet, or other sharp object. Penetration brain injuries are serious medical emergencies. Of those who survive a penetrating brain injury, about half get late-onset epilepsy.

An object traveling at a high rate of speed, such as a bullet, may pass entirely through the head and exit on the opposite side, creating a perforating or through and through head injury. A bullet can also be a low velocity projectile and can rebound within the confines of the skull, damaging a large area. The destruction caused by firearms is considerable, and firearms cause more fatalities that any other causes of traumatic brain injury.

Second Impact Syndrome

Second Impact Syndrome (SIS), refers to when an individual suffers a second traumatic brain injury before the symptoms of an earlier traumatic brain injury have completely healed. It is also known as recurrent traumatic brain injury, and is a rare, but extremely dangerous medical condition. The second impact can be fatal even if it is minor and does not involve loss of consciousness. It is believed that the second blow to the head can impede the body’s ability to autoregulate blood flow to the brain. As a result, the brain swells and intracranial pressure (ICP) increases, displacing the brain. The time from the second impact to complete brainstem failure is brief, usually occurring in fewer than five minutes. Second impact syndrome can affect athletes who return to play too soon after an initial traumatic brain injury. If second impact syndrome occurs, there is very little hope for recovery.

Skull Fractures

Although the skull is resilient and provides excellent protection for the brain, skull fractures can occur when trauma to the head causes a break in one or more of the cranial bones. Falls, motor vehicle accidents, assult, and sporting accidents are some common causes of head trauma. Skull fractures may be coupled with a more serious brain injury, especially if the fracture causes damage to a major blood vessel or brain tissue.

Skull fractures can be roughly divided into five categories: simple, compound, linear, depressed, and basilar.

A simple skull fracture is a break in the bone with no damage to the skin. A compound skull fracture involves a break in the skin and splintering of the bone. A linear skull fracture refers to a relatively simple and straight break in the skull bone. Unless there is injury to the brain, a linear skull fracture is not a serious injury. In rare instances, due to brain swelling, a linear fracture can grow and cause more dangerous complications. A diastatic fracture is a type of linear fracture in which skull bones seperate before they have entirely fused. This type of fracture can occur in youg children due to impact with a broad surface. Depressed skull fractures are less common but more serious then linear fractures. Depressed skull fractures are usually the result of a trauma caused by heavy but small objects, such as rocks, hammers, etc. The injury presents itself as a dent or depression in the skull, which may put pressure on the brain. If the depth of the depression is equal to or greater than the thickness of the skull, surgery is usually necessary in order to raise the bones and make certain that the brain was not injured. Smaller depressions typically do not require surgery unless additional injuries are found. When a depressed skull fracture is comminuted, the skull bone is broken into a number of pieces, greatly increasing the risk that brain will be lacerated by the sharp bits of bone Basilar skull fractures are quite rare, occurring in about 4 percent of severe head injuries. A basilar skull fracture occurs when a considerable force breaks the bones forming the base of the skull. Because basilar skull fractures frequently connect to the sinus cavities (allowing are into the skull), there is a greater risk of infection. Surgery is usually not necessary, unless other conditions necessitate it.

Brain Swelling

Brain swelling, also known as cerebral edema, occurs when there is an increase in the amount of fluid to the brain, and often follows a brain injury. Because the brain is confined within the space of the skull, swelling of the brain results in increased intracranial pressure (ICP). The pressure can cause further damage to the brain by forcing it against the abrasive interior of the skull. ICP can be extremely dangerous, causing physical and mental impairment and even death. Controlling intracranial pressure depends on intensive monitoring and control of every bodily function; this requires around-the-clock medical attention and usually takes place in an intensive care unit. Very strong medications are given to temporarily paralyze the head injured person, and even deepen his level of unconsciouness, in order to control his breathing, blood pressure and other vital functions. In some cases removal of small amounts of fluid from around the brain through surgical procedures may help.

Brain Tearing

Brain Tearing refers to microscopic breaks in the delicate tissues and nerves of the brain that result from a trauma to the head. Tearing in the brain is a serious medical issues; it can damage to the nerve system and impair bodily function. Every tear in the brain results in the cutting of a neurotransmission (a severing of the brain's wiring). One of the major problems with brain tearing is that it happens on a microscopic level and is very difficult to detect. It may not show up on x-rays, MRI’s and CAT-scan’s, which are effective for diagnosing larger areas of brain damage, but often fail to detect small brain tears.

Shaken Baby Syndrome

Shaken Baby Syndrome (SBS) is a violent form of child abuse that often results in permanent brain damage to the infant. Shaken baby syndrome occurs when someone (usually a parent, guardian, or babysitter) aggressively shakes a baby. This is usually due to the caretaker's stress and/or frustration, such as when an infant cries continually. Infants’ neck muscles cannot support their disproportionately heavy heads, and the whiplash motion causes their brains to collide against the walls of the skull. The degree of brain damage caused by SBS depends on the amount and duration of the shaking and the forces involved in impact on the head. In addition, there may be retinal hemorrhages, damage to the spine, and further injuries. Victims are usually younger than 2 years old, but it can occur in children up to the age of 5.

Symptoms of SBS include:

Difficulty breathing Seizures Rigidity Vomiting Changes in eating patterns Pale or bluish skin convulsions Extreme lethargy Inability to lift head Inability to focus eyes

If a child survives SBS, he or she will likely have handicaps ranging from mild (such as learning disorders and behavioral changes) to moderate and severe (such as mental and developmental retardation, paralysis, and blindness).

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