Limitations in Diagnostic and Prognostic Capabilities
At one time, clinicians believed that traumatic brain injury could be diagnosed fairly easily based solely on symptomatology. This notion has now been soundly discredited. What has become apparent—especially in the past few years with advances in brain mapping and extensive studies regarding the pathophysiology of TBI—is that there exists a lack of reliable diagnostic tools for determining the relationship between changes in brain structure and long-term functional prognosis following the acute phase of traumatic brain injury.
Limitations of CT Technology in Detecting Microbleeds
CT scans were once the favored tool in diagnosing and managing TBI. The problem is that CTs do not pick up diffuse axonal injury (DAI) and only rarely show minute hemorrhages in brain capillaries, known as petechial hemorrhages. Advances in MRI imaging, though, have made it possible to begin exploring the correlation between DAI lesions and long-term neurological outcomes.
Cerebral Atrophy Progression Associated with Injury Severity
Cerebral atrophy is a common result of TBI. Studies have documented that following a moderate to severe TBI, the total brain volume will begin decreasing within the acute phase (defined as within three weeks) and reach a significant peak 8-12 months later. Subsequent brain volume loss will continue at a rate greater than observed in normal aging for as long as three years after injury. Similar findings have also been noted in patients with mild TBI.
Total brain volume loss has been significantly tied to several indicators of the severity of the injury, including:
- Admission Glasgow Coma Score (GCS), a neurological scale that is used to characterize the level of consciousness in a person following TBI
- Duration of coma
- Post-traumatic amnesia
However, the correlation between brain atrophy and prognosis for eventual functional recovery is more difficult to assess. Paradoxically, the general cerebral atrophy in the chronic phase (>6 months) is more highly correlated with the severity of the injury as opposed to functional prognosis (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2858299/).
Accuracy of Imaging Tools
Fluid attenuated inversion recovery (FLAIR) is a pulse sequence (signals) used in MRIs to detect brain abnormalities. Researchers studying FLAIR signals have recently concluded that abnormal FLAIR lesions characterized by acute hyperintensity are strongly predictive of global brain atrophy following TBI. However, researchers caution that FLAIR technology may not be the most sensitive MR to detect DAI. Newer, more sophisticated forms of imaging, such as 3D gradient echo MRI imaging or susceptibility-weighted imaging (SWI)—is far more sensitive in detecting microbleeds than earlier forms of MRIs. Diffusion weighted imaging, also known as DWI, has proven to be highly effective for detecting of cytotoxic cerebral edema –a type of brain edema in which the blood-brain barrier remains intact—in cases of acute stroke. However, it has shown no more sensitivity in identifying DAI lesions that FLAIR.
Other programs, including SIENA (Structural Image Evaluation, using Normalization, of Atrophy) and SIENAX are now being used to measure temporal brain change by inputting two MRI images, taken at different points in time, and then comparing the two images for signs of atrophy. SIENA has also been modified to a single-time point method which measures atrophy state rather than rate.
It is not unusual for many scans to be taken within the first week or within the first days following TBI. Ideally, scans obtained within the first 24 hours of a suspected TBI should be studied for differences with images taken during the subacute (>3 months) or chronic stage (>6 months) as it is possible that FLAIR lesions can be more easily spotted over time.
White Matter versus Gray Matter
Post-concussion syndrome is a complex disorder in which various symptoms — such as headaches and dizziness — last for weeks, months and even years after the initial injury. The syndrome has been poorly understood because it does not seem to be correlated with the severity of the initial injury. 20-30% of people who sustain MTBI will develop some degree of post-concussion syndrome. Until recently, clinicians did not understand why someone with a relatively mild injury could develop severe and prolonged impairment. Now brain researchers believe they may have found the answer with new insight into the “white matter” of the brain.
Gray matter is located in the outermost portion of the brain and contains neurons, the specialized cells responsible for storing and processing information: i.e., learning and memory. For years, scientists believed that brain injuries disproportionately affected the brain’s gray matter. In fact, white matter was considered pretty much of a passive tissue, having little to do with learning and brain functions. More recently, white matter has been found to “matter” very much, serving to regulate signaling, distributing and relaying communication messages to different parts of the brain.
In 2014, researchers working at the University of Southern California discovered that white matter contains the scaffolding network that defines the information architecture comprising and supporting brain function. By mapping the brain’s white matter, these researchers also discovered that the most important areas of white matter and gray matter do not always overlap. Instead, white matter is sometimes responsible for signaling messages to remote areas of the brain. When white matter pathways sustained damage, brain areas served by that pathway either withered or had their functions taken over by other parts of the brain. This finding may help explain why someone with MTBI can suffer what appear to be disproportionately devastating effects (http://journal.frontiersin.org/Journal/10.3389/fnhum.2014.00051/abstract).
Who is at Greatest Risk and Precautions
Males are at higher risk of experiencing TBI than women. Youngest children and older adults are at highest risk for sustaining fall-related TBIs. Adolescents and young adults (15-24 years old) have the highest rates of motor vehicle-related TBIs. Older adults, ages 65 years and older, have the highest rate of hospitalizations resulting from TBI and are most likely to die from either TBI or TBI complications.
Simple Tips for Preventing TBI
- Always wear a seat belt when driving or riding in a car.
- Make sure that your child or baby is properly buckled into a carseat, booster seat or seatbelt (depending on age and weight).
- Always wear a helmet when riding a bike, playing contact sports like football, baseball or ice hockey or when using in-line skates, skateboard, snowboard or skiing, and make sure that your child does too!
- Always wear a helmet when riding a horse
- Make sure that your child’s playground has ground surface that is shock-absorbent
- Keep firearms unloaded and bullets in a locked cabinet.
- Use sturdy stepstools or grab bars when trying to reach objects on high shelves.
- Install handrails on stairways.
- Install window guards to keep young children from falling out.
- Use safety gates at the top and bottom of all stairways when there are young children in the house.
Older adults are at particularly high risk for falling and sustaining a TBI. Keep these easy tips in mind when safety-proofing or “seniorizing” their house or apartment.
- Tack or tape all loose rugs or carpets to the floor.
- Install grab bars for seniors in showers and bathtubs.
- Tack, staple of tape loose electrical cords to the floor so they do not pose a tripping hazard
- Place soft towels around sharp corners of furniture and appliances.
- Install elevated toilet seats to allow greater ease in getting on and off the toilet. Also install grab bars by the toilet for extra assistance and stability in getting up from the toilet.
- Place no-slip mats around kitchen and bathroom sinks where the floor is likely to get splashed with water.
- Install railings on BOTH sides of stairways.
- Install telephones at the bottom of every stairway and make sure that your elderly loved one always wears a lifeline alert so that if he/she falls, she can call for help quickly.