Types of Brain Injuries

Brain injuries are devastating injuries that occur every 15 seconds in the United States. Brain injuries are the leading cause of death in persons under the age of 45. There are approximately 5 to 6 million people living in the U.S. with brain injuries. Leading causes of brain injuries are motor vehicle accidents, falls, violence and sports injuries.

The brain can be damaged in multiple ways. In order to understand head injuries, it is useful to understand the different types of brain injuries that can occur:

Concussions – A concussion can be defined as a sudden alteration of the conscious state induced by trauma. The person affected may lose consciousness briefly and may be confused following. The brain can recover from a concussion but in certain circumstances, there may be residual damage. Concussions often occur in sports-related injuries.

Contusions – When the head strikes a hard, immovable object the brain may be bruised. Contusions are essentially bruises that result in damage to, or destruction of, brain tissue. They often occur in the frontal and temporal lobes. These are the lobes where behavior and memory centers are located, so damage to these areas can cause changes in behavior, changes in vision (including loss of vision), impairment of memory and occasional weakness or loss of coordination.

Diffuse axonal brain injuries (DAI) – In this type of injury, a shearing force damages nerve fibers or stretches blood vessels in the brain. The result may be hemorrhage (bleeding) and can also cause a cascade of chemicals that are toxic to the brain to be released. The temporal and frontal lobes are often affected. Symptoms of DAI include inattentiveness, problems with memory and disorganization.

Hypoxic-Ischemic brain injuries (HII) – Stroke is a common cause of this type of injury, in which the amount of oxygen is reduced to the brain (for example, from a blood clot). The injury causes brain swelling that restricts oxygen, glucose and other necessary nutrients from reaching the brain. A poor prognosis is associated with both HII and DAI in terms of cognitive function and memory impairment, if the patient survives the initial injury.

Hemorrhage – A cerebral or intracranial bleed occurs when blood vessels within the brain bleed as a result of trauma or inherent weakness of a blood vessel (e.g. aneurysm). Hemorrhages may be tiny or large and symptoms correspond to the severity and location of the bleed. Hemorrhage does not always occur immediately after an injury, but may be delayed for hours or even days.

Infarction– “Infarction” is the medical term for stroke. Strokes occur when an artery supplying the brain is blocked, cutting off oxygen and nutrients to the brain. Speech, language and visual problems often occur after a stroke.

Hematomas – Hematomas develop outside the brain. Subdural hematomas occur over the surface of the parietal or frontal lobes. A subdural hematoma is slow bleeding outside the brain caused by a vessel carrying venous (unoxygenated) blood. Epidural hematomas are usually caused by damaged arteries, which carry blood under pressure, which can cause severe pressure which must be released immediately or death will occur. Subarachnoid hemorrhages occur when bleeding spreads slowly over the brain surface. Subarachnoid hemorrhages rarely cause death and may even be symptomatic.

There are numerous types of injuries which may be caused by trauma or physical conditions. Understanding the type of injury sustained can provide clues as to what to expect in terms of symptoms and outcome. Any time a brain injury is suspected, medical attention must be sought. Brain injuries can cause permanent and severe damage when not treated. With proper treatment, many patients recover.