Traumatic Brain Injury (TBI) and Concussion
What is TBI?
We are all increasingly aware of traumatic brain injury (TBI), whether through the news, media or personal experience, but what exactly is TBI? TBI is a physical injury to the brain, which has many causes including vehicle crashes, falls, assault, contact sports and military combat. Because the brain supervises and controls almost all aspects of normal human function, physical, psychological, hormonal or otherwise, injury to the brain (TBI) may result in a wide array of medical, psychological and behavioral problems. While many symptoms, such as headache, memory problems, difficulty concentrating and visual changes, are common among TBI patients, rarely will two individuals experience exactly the same problems due to TBI.
TBI may occur when force is applied to the brain, either through a direct impact to the head or its rapid acceleration and deceleration, as in whiplash. However, every blow to the head will not necessarily result in TBI in every individual. Similarly, the severity of trauma to the head does not necessarily determine the severity of a TBI, when it occurs.
TBI ranges in degree from severe to mild. The most severe cases may result in immediate or later death of the patient. However, more than 75% of TBIs are mild and referred to as concussion; concussion is also a physical injury to the brain. The good news about concussion is that most patients recover over a relatively brief period of time. Some concussion patients, however, will experience persistent problems related to their TBI. Multiple concussions may increase the risk for long-term problems and have been linked to the development of delayed brain degeneration.
TBI affects the brain in two major ways. First, actual bruising or tearing of brain tissue and bleeding within or surrounding the brain may occur, with subsequent brain swelling (edema). These injuries occur in more severe forms of TBI and are typically absent in mild TBIs. Second is injury to microscopic nerve fibers (axons), which constitute the “wiring” that connects nerve cells in the brain (neurons) to each other and to the rest of the body. This microscopic injury leads to many of the persistent problems which TBI patients may experience.
How is TBI diagnosed?
TBI is a clinical diagnosis; no single test is able to definitively confirm the diagnosis of TBI. Doctors assess the history of the injury, the patient’s symptoms, the physical examination and additional tests, including neuroradiology, to confirm a diagnosis of TBI. Many TBI patients experience a loss of consciousness (blacking out) at the time of their injury. Loss of consciousness most commonly lasts from seconds to minutes, but in severe TBI may last for days (coma) and in the most severe cases may persist indefinitely. Patients with mild TBI (concussion) may not experience any loss of consciousness. Most TBI patients have some degree of amnesia (loss of memory) for the minutes to hours or longer surrounding their injury.
how is neuroradiology used in the diagnosis of TBI?
Neuroradiology is an essential tool in the care of TBI patients. It plays two distinct roles depending on the time at which the patient is assessed. In the period immediately after the injury, CT scans are most commonly used to diagnose acute problems which may be life threatening and require emergent treatment such as surgery. The CT scan is fast and widely available. It is highly effective in detecting bleeding within and surrounding the brain (hematomas) as well as brain swelling (edema), which may require emergency surgery. When urgent surgery is not needed, repeat CT scans may be used to follow the resolution of injuries. CT is much more limited in its ability to detect the widespread microscopic injury to axons (nerve fibers) which leads to many of the long term problems experienced by TBI patients; it is not unusual for the CT scan to be entirely normal in a patient with TBI. In fact, the CT scan is typically normal in patients with milder TBI including concussion. CT scan is also effective for detecting skull fractures, although these rarely require emergency treatment.
Following the acute period after TBI, neuroradiology is used to detect injury, especially indications of microscopic injury to axons (nerve fibers), which can explain the persistence or worsening of symptoms related to TBI. Magnetic resonance imaging (MRI) is a powerful diagnostic tool that can detect signs of injury such as minute bleeding (microhemorrhage), small areas of bruising (contusion) or scarring (gliosis), which are invisible to the CT scan. Newer, specialized types of MRI can assess brain structure at an even finer level or measure brain function to detect alterations in brain structure and function due to TBI. Because microscopic injury to the brain may be a cause of problems, however, even MRI may not be able to detect any abnormality in a patient with TBI. Long after the injury, MRI as well as CT may demonstrate brain atrophy, which results when dead or injured brain tissue is reabsorbed following TBI. Because injured brain tissue may not completely recover following TBI, changes due to TBI may be detectable many years after an injury.
What to do if you experience a head injury
Following a head injury, you should be assessed by a medical professional with expertise in the assessment of TBI. This might be an emergency medicine physician, neurologist, neurological surgeon or other physician. In particular, a physician should evaluate all patients who experience loss of consciousness as soon as possible after the injury, often in an emergency department. Because all patients with head injuries do not require imaging, the physician will assess the patient and determine whether CT or MRI is necessary. Patients who have persistent problems or symptoms following a head injury should consult a medical professional, a neurologist, psychiatrist or physiatrist, for example, who will determine, based on their medical assessment, whether MRI is necessary. Patients living with the effects of TBI may obtain helpful information from the following advocacy organizations: