Brain Injury: An Overview - What is it and what does it affect?
Reviewed January 2008
The brain is the control center for the body. It manages many things such as breathing, moving and vision. The brain also controls thinking, emotions and behavior. An injury to the brain can affect almost any function of the body and can sometimes affect personality.
Each area of the brain involves different functions (see illustration), but sometimes there is overlap so that more than one location controls a function. Every brain injury is different so no two people will have identical symptoms. One person may have problems with memory and concentration while another may have weakness or paralysis of muscles. Almost any mix of symptoms or impairments can occur.
Areas of the brain
• The left side (hemisphere) controls the right side of the body and vice–versa. An injury to the right side of the brain can cause weakness or paralysis on the left side of the body.
• The ability to use language is generally controlled by the left hemisphere; damage to this area will cause difficulty with understanding or speaking.
• The back of the brain controls vision.
• The right side of the brain controls spatial skills.
• The brain stem controls basic body functions (breathing, blood pressure and swallowing).
• The front of the brain controls motivation, emotion and behavior.
• The bony skull covers the brain and helps protect it from injury.
Only a limited space for the brain exists in the skull, however. If the brain swells after traumatic brain injury, it can get compressed and damaged.
• Ventricles are hollow spaces within the brain that are filled with cerebrospinal fluid. In brain injury, the drainage system of these ventricles can get damaged. This results in a build up of fluid known as hydrocephalus.
• Traumatic brain injury often affects many parts of the brain rather than just a single region. Thus, the effects of a brain injury may not always be clearly defined but will depend on the location and the amount of damage to particular brain parts.
Symptoms of Traumatic Brain Injury
Physical impairments
• muscle weakness or paralysis
• loss of coordination
• problems with vision or smell
• slurred speech
• difficulty swallowing,
• spasticity (severely increased muscle tone)
• pain
Cognitive (thinking) impairments
• poor memory
• lack of concentration
• slowed thinking
• inability to plan ahead
• problems with perception
Emotional and behavioral issues
• lack of awareness of problems
• depression
• irritability
• poor judgment
• low motivation
• poor emotional control
• agitation
Types of Non–Traumatic Brain Injury
Many different situations can cause damage to the brain. Traumatic brain injury is the most common type, but non–traumatic injury includes:
• Anoxic injury – The brain does not receive adequate oxygen, most commonly after cardiac arrest, when there is little or no blood flow to the brain. Most common results are problems with memory and muscle coordination.
• Toxic or metabolic injury – Occurs after exposure to unsafe substances, such as lead, or a harmful buildup of the body's own chemicals, as in kidney failure.
• Encephalitis – Occurs when there is an infection of the brain, most often due to a virus.
Although the consequences of non–traumatic brain injury are often similar to those seen with a traumatic brain injury, there are important differences. Discuss these differences with your health care team.
Penetrating and Non–Penetrating Brain Injuries
Traumatic brain injury occurs as a result of any strong force to the head. Penetrating and non–penetrating injuries are the two main types.
Penetrating, also known as open head injury, occurs whenever an object goes through the skull and damages the brain underneath. The most frequent causes of penetrating head injury are gunshot wounds. This type of injury usually damages specific parts of the brain and spares others. People may have fewer impairments after this type of injury than they do after non–penetrating injury.
Non–penetrating or closed head injuries occur when the skull is not significantly damaged, but the brain inside is. Examples are injuries from automobile collisions or from being struck in the head with a hard object. The impact whips the brain back and forth inside the skull. This causes twisting and tearing of delicate brain tissue, as well as bruises (contusions) where the brain knocks against the skull. Arteries and veins can be stretched and torn, causing leakage of fluid, or even bleeding. The damage in closed head injury is rarely confined to a single area. Most often, it affects large parts of the brain – especially those that control being awake and aware.
Secondary Brain Injury
Although much damage is caused by the initial impact (primary injury), additional factors can cause more problems. These are called secondary injury. Most of the care that a person receives in the hospital after a brain injury is meant to minimize the effects of secondary injury since the primary injury (the impact) has already happened.
A major cause of secondary injury is increased intracranial pressure, usually caused by swelling of the brain. Since the brain has no room to expand, it gets pressed up against the skull. This pressure causes damage to the brain tissue. In addition, the pressure can cut off blood flow to the brain, causing further damage. A number of things can help minimize brain swelling including medicines, hyperventilation on a ventilator or even surgery to open the skull and relieve some of the pressure.
Another main cause of secondary injury is bleeding in or around the brain. During the acute hospitalization, doctors watch for developing blood clots (hematomas) that can cause damage to the brain tissue directly and cause build up of dangerous amounts of pressure within the skull. This can also affect drainage in the brain and cause fluid to build up (hydrocephalus). Sometimes hematomas need to be drained surgically.
Other medical problems, which are common after trauma, can aggravate a brain injury. Low blood pressure or low blood oxygen due to breathing difficulty can cause further damage to the already–injured brain. Infections, blood abnormalities and seizures can also affect brain function.
Damage to the brain is caused by many factors in addition to the original trauma. Brain injury represents all these different factors together.
Each area of the brain involves different functions (see illustration), but sometimes there is overlap so that more than one location controls a function. Every brain injury is different so no two people will have identical symptoms. One person may have problems with memory and concentration while another may have weakness or paralysis of muscles. Almost any mix of symptoms or impairments can occur.
Areas of the brain
• The left side (hemisphere) controls the right side of the body and vice–versa. An injury to the right side of the brain can cause weakness or paralysis on the left side of the body.
• The ability to use language is generally controlled by the left hemisphere; damage to this area will cause difficulty with understanding or speaking.
• The back of the brain controls vision.
• The right side of the brain controls spatial skills.
• The brain stem controls basic body functions (breathing, blood pressure and swallowing).
• The front of the brain controls motivation, emotion and behavior.
• The bony skull covers the brain and helps protect it from injury.
Only a limited space for the brain exists in the skull, however. If the brain swells after traumatic brain injury, it can get compressed and damaged.
• Ventricles are hollow spaces within the brain that are filled with cerebrospinal fluid. In brain injury, the drainage system of these ventricles can get damaged. This results in a build up of fluid known as hydrocephalus.
• Traumatic brain injury often affects many parts of the brain rather than just a single region. Thus, the effects of a brain injury may not always be clearly defined but will depend on the location and the amount of damage to particular brain parts.
Symptoms of Traumatic Brain Injury
Physical impairments
• muscle weakness or paralysis
• loss of coordination
• problems with vision or smell
• slurred speech
• difficulty swallowing,
• spasticity (severely increased muscle tone)
• pain
Cognitive (thinking) impairments
• poor memory
• lack of concentration
• slowed thinking
• inability to plan ahead
• problems with perception
Emotional and behavioral issues
• lack of awareness of problems
• depression
• irritability
• poor judgment
• low motivation
• poor emotional control
• agitation
Types of Non–Traumatic Brain Injury
Many different situations can cause damage to the brain. Traumatic brain injury is the most common type, but non–traumatic injury includes:
• Anoxic injury – The brain does not receive adequate oxygen, most commonly after cardiac arrest, when there is little or no blood flow to the brain. Most common results are problems with memory and muscle coordination.
• Toxic or metabolic injury – Occurs after exposure to unsafe substances, such as lead, or a harmful buildup of the body's own chemicals, as in kidney failure.
• Encephalitis – Occurs when there is an infection of the brain, most often due to a virus.
Although the consequences of non–traumatic brain injury are often similar to those seen with a traumatic brain injury, there are important differences. Discuss these differences with your health care team.
Penetrating and Non–Penetrating Brain Injuries
Traumatic brain injury occurs as a result of any strong force to the head. Penetrating and non–penetrating injuries are the two main types.
Penetrating, also known as open head injury, occurs whenever an object goes through the skull and damages the brain underneath. The most frequent causes of penetrating head injury are gunshot wounds. This type of injury usually damages specific parts of the brain and spares others. People may have fewer impairments after this type of injury than they do after non–penetrating injury.
Non–penetrating or closed head injuries occur when the skull is not significantly damaged, but the brain inside is. Examples are injuries from automobile collisions or from being struck in the head with a hard object. The impact whips the brain back and forth inside the skull. This causes twisting and tearing of delicate brain tissue, as well as bruises (contusions) where the brain knocks against the skull. Arteries and veins can be stretched and torn, causing leakage of fluid, or even bleeding. The damage in closed head injury is rarely confined to a single area. Most often, it affects large parts of the brain – especially those that control being awake and aware.
Secondary Brain Injury
Although much damage is caused by the initial impact (primary injury), additional factors can cause more problems. These are called secondary injury. Most of the care that a person receives in the hospital after a brain injury is meant to minimize the effects of secondary injury since the primary injury (the impact) has already happened.
A major cause of secondary injury is increased intracranial pressure, usually caused by swelling of the brain. Since the brain has no room to expand, it gets pressed up against the skull. This pressure causes damage to the brain tissue. In addition, the pressure can cut off blood flow to the brain, causing further damage. A number of things can help minimize brain swelling including medicines, hyperventilation on a ventilator or even surgery to open the skull and relieve some of the pressure.
Another main cause of secondary injury is bleeding in or around the brain. During the acute hospitalization, doctors watch for developing blood clots (hematomas) that can cause damage to the brain tissue directly and cause build up of dangerous amounts of pressure within the skull. This can also affect drainage in the brain and cause fluid to build up (hydrocephalus). Sometimes hematomas need to be drained surgically.
Other medical problems, which are common after trauma, can aggravate a brain injury. Low blood pressure or low blood oxygen due to breathing difficulty can cause further damage to the already–injured brain. Infections, blood abnormalities and seizures can also affect brain function.
Damage to the brain is caused by many factors in addition to the original trauma. Brain injury represents all these different factors together.
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