Traumatic brain injury (TBI) is any injury to the brain that results in structural damage to brain tissue and/or disrupted brain function. The injury may be caused by direct trauma (blunt force) or indirect trauma (whiplash or inhalation of toxic fumes) to the brain. TBI can vary in degree – mild, moderate and severe – and can cause temporary or permanent impairment. The damage may occur at the time of the injury or may develop later due to swelling and bleeding inside the head
A mild brain injury is a traumatic brain injury (TBI) can be classified as mild if loss of consciousness and/or confusion and disorientation is shorter than 30 minutes. Even though this type of TBI is called “mild,” the effect on the family and the injured person can be devastating.
Unlike moderate or severe traumatic injury, where the impairments caused by the injury are rarely doubted, mild brain injury often goes unrecognized and is sometimes never detected. The injured individual may not be aware of the extent of their injuries until they attempt to return to normal living and even then, they may not be able to determine why things don’t seem “normal.” All but “mild” TBI is usually accompanied by an immediate loss of consciousness (coma) and post-traumatic amnesia.
Moderate brain injury is defined as a brain injury resulting in a loss of consciousness from 20 minutes to 6 hours and a Glasgow Coma Scale of 9 to 12.
Moderate to severe TBI can cause permanent physical or mental disability. Because polytrauma (two or more severe injuries in at least two areas of the body) is common with moderate to severe TBI, many patients face additional disabilities as a result of other injuries. Even patients who appear to recover fully may have some long-term symptoms that never completely go away.
These ongoing challenges can also affect the patient’s personal life. People who have experienced brain injuries may take longer to do cognitive tasks associated with memory. Family relationships are almost always affected and in some cases the patient will be dependent on their caregivers.
Severe brain injury is defined as a brain injury resulting in a loss of consciousness of greater than 6 hours and a Glasgow Coma Scale of 3 to 8.
The Glasgow Coma Scale (GCS) rates the brain injury survivor’s ability to open their eyes and respond to verbal commands and motor stimuli. Each level indicates a level of brain injury. The lowest possible cumulative score for the four sections is 3 (no response); the alert and oriented survivor is rated at 15.
A Glasgow Coma Scale (GCS) of:
Acquired brain injury (ABI) refers to brain damage caused by events after birth, rather than congenital or
neurodegenerative disorders. ABI includes both traumatic brain injury (physical trauma due to accidents, assaults and neurosurgery, for example) and non-traumatic brain injury (caused by strokes, brain tumours, infection, poisoning, hypoxia, ischemia, encephalopathy or substance abuse).
Traumatic Brain Injury (TBI) is a subset of “head injury.” The terms “head injury” and “brain injury” are often used incorrectly and interchangeably. Head injuries are caused by trauma to the head, skull or scalp, but do not always result in injury to the brain itself.
Some brain injuries are “closed head injuries,” where the skull has not been penetrated or fractured into brain tissue. Though survivors may not exhibit external signs of injury, a closed head injury can cause widespread damage and result in extensive, or “global,” neurological deficits. The injury can also be categorized as ‘mild,’ ‘moderate’ or ‘severe.’ These deficits can range from partial to complete paralysis; cognitive, behavioural and memory dysfunction; a persistent vegetative state; or death.
Skull fracture is a break in the bone that surrounds the brain. The fracture may heal on its own or, if there is tissue damage below the fracture, require remedial surgery. A skull fracture can be depressed, meaning part of the skull is pushed into the brain, but even a non-depressed skull fracture is very serious.
An anoxic brain injury is caused by a lack of oxygen to the brain. It usually results from lack of blood flow due to injury or bleeding and will cause the swelling of brain tissue. It may be secondary to trauma, accident, or sometimes medical malpractice.
Contusion or concussion is often mislabelled as a “mild” injury to the brain resulting in bruising of brain tissue. This injury may cause headaches, vomiting, dizziness and problems with memory or concentration. It does not require surgery. While there is often little or no loss of consciousness, the long-term results may not be “mild.”
A coup injury is caused when the brain is thrust against one side of the skull. Because brain tissue is suspended in fluid, it often rebounds and collides with the opposite side of the skull. When it strikes both sides of the skull, the injury is sometimes called a coup-contrecoup injury.
Diffuse axonal injury (DAI) results when a rotational or shearing force is exerted on the nerve fibres. DAI may cause a loss of consciousness, or coma, which may last from a short time to an indefinite period.
The rotational force of this injury causes a shearing of the nerve connections and pathways. These pathways may tear and be lost, and once they are gone they cannot be rebuilt. The brain must then attempt to find alternate pathways to resume the functions of the severed paths.
DAI can be particularly devastating, because the brain stem is a critical relay station. It controls consciousness, alertness and basic bodily functions. Especially frustrating is that these injuries are microscopic and usually cannot be detected in radiographic studies, such as CT scans or routine MRI scans. Fortunately, improving technology is allowing DIA to be shown in higher resolution MRI scans.
Epidural hematoma is a build-up of blood between the skull and the top lining of the brain (dura). This clot may cause pressure changes in the brain, and emergency surgery may be necessary. Surgery may be needed depending on the size of the clot. This bleeding may increase pressure on the brain, which forces it down the spinal column, compressing the brain stem and resulting in death. This is a neurosurgical emergency.
An intra-cerebral hemorrhage is a blood clot deep in the middle of the brain that is hard to remove. Pressure from this clot may cause tissue damage, and surgery may be needed to relieve the pressure.
A subdural hematoma refers to the formation of a blood clot between the brain tissue and the dura. If it occurs slowly over several weeks it is referred to as a subdural hematoma; if it occurs quickly it is referred to an acute subdural hematoma. The clot may cause pressure and need surgery to have it removed.
When the injured survivor cannot be awakened or aroused by any means, they are in a state of unconsciousness known as a coma. Clinically described, it is an inability to follow a one-step command consistently. This term, as well as the description ‘loss of consciousness,’ are used colloquially and incorrectly all the time. Court cases may involve arguments about the legal definitions of these terms.
Immediately after a TBI, the injured person is often disoriented and unable to remember events that occur after the injury. This state of confusion is called post-traumatic amnesia (PTA). The person may not remember their name, where they are, and what time it is. When continuous memory returns, PTA is considered to have resolved. If PTA lasts, new events cannot be stored in the memory. During PTA, the individual’s consciousness is “clouded.”
There are two types of amnesia: retrograde amnesia (loss of memories that were formed shortly before the injury) and anterograde amnesia (problems with creating new memories after the injury has taken place). Both retrograde and anterograde forms may be referred to as PTA, or the term may be used to refer only to anterograde amnesia.
The duration of PTA is sometimes used, on its own or in conjunction with the Glasgow Coma Scale and other methods, to measure the severity of traumatic brain injury. It is important to note that even a “very mild” injury may have long-term, serious consequences for a survivor.