Thinking Inside the Box: Imaging Technology Offers New Insights into Traumatic Brain Injury

(Editor’s note: This article from a past issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)


On January 8, 2011, Congresswoman Gabrielle Giffords was holding a meet-and-greet with constituents outside a Tucson grocery store when a young man approached, raised his arm, and shot her in the head at point-blank range. The 9 mm bullet entered near her left eye, passed through the brain and exited the left rear of her head. Giffords, 40 years old, survived the assassination attempt, but was left with traumatic brain injury (TBI) and a long and arduous road to recovery. The injury left her with aphasia, problems with hand-eye coordination and some cognitive challenges associated with injury to the left hemisphere and frontal region.

Like Giffords, every year more than 1.7 million people are diagnosed with brain injury as a result of traumatic external forces (car accident, fall, gunshot wound) and internal incidents (stroke, tumor, aneurism). We are only now beginning to grasp the scope of brain injury — not only in the highly publicized accounts of sports and combat veterans, but also in prison populations, the elderly, and victims of violence or abuse. The writing is dark and indelible: Brain injury, especially to the frontal area that governs mood and behavior, can have devastating effects on a person’s life.

But there is hope. Researchers at Pate Rehabilitation in Dallas and the University of Texas at Arlington are looking at developing more effective treatments for people with TBI through the use of imaging technology.

A DIFFICULT DIAGNOSIS

To understand what happens to the brain in an accident, visualize an egg. The brain is a bit like a 3.5-pound yolk floating in a sac of cerebrospinal fluid inside the skull. If that egg is violently shaken, the yolk gets damaged. Similarly, in an accident, the brain bounces forward, hitting the frontal lobes against the skull, and then back, damaging the underside of the brain, and stretching and tearing delicate axonal fibers and gray matter. If there’s rotation involved, the damage can be much worse — scrambling the yolk, if you will.

Giffords suffered injury to her left hemisphere, the part of the brain that controls language, as well as to her ability to see out of her right eye and to move the right side of her body. She also sustained damage to her frontal lobes. Injury to this area, even if slight, may profoundly impact a person’s daily life, since it can diminish reasoning, impulse control, and behavioral stability.

For all the havoc it wreaks, TBI often goes undiagnosed. For one, this type of injury can lead to changes in mood and impairment of such executive functions as decision-making, reasoning, and planning, which are not readily seen or may be attributed to other causes. For another, there’s no broken bone, no bleeding gash, so brain injury can be easily overlooked — especially if a physician is treating a visible injury. Your son may get clocked by a ball and briefly pass out, but once the headache and welt subside, it’s hard to know whether the concussion will have lasting impact. Then there’s the problem that many of the symptoms may not be specific to the area of injury.

It is easy to tell how a bone or a muscle is healing. X-rays or muscle-strength tests tell us how the patient is doing over time. But how do you tell if a damaged brain is getting better? The only way to really know what’s going on is to look inside the brain itself.

INSIDE THE BLACK BOX

Functional near-infrared spectroscopy (fNIRS) has been used for a decade to study prostate cancer, breast tumors, and brain oxygenation by measuring change in the amount of light absorbed by oxygenated and deoxygenated blood in tissue. These changes relate directly to the amount of oxygen used to fuel neuronal activation. Researchers at Pate Rehabilitation and the University of Texas at Arlington are applying that technology to functional brain imaging, giving them a real-time look at the brain’s neuronal activity.

This type of imaging works by shining an array of infrared light beams onto the scalp. Similar to shining a flashlight on your hand, the light penetrates the skin and bone of the head and, depending on how much oxygen is present in the blood, is either scattered or absorbed in the cortex (the gray matter of the brain). Since nerves in the brain need more oxygen when they’re working, this system is able to measure neuron activity by measuring increases and decreases in oxygen. The fNIRS device can take up to 10 images per second, giving a 2-D moving picture of what’s happening in the brain.

The benefits of fNIRS over other brain imaging methods such as functional magnetic resonance imaging (fMRI) or X-rays, positron emission tomography (PET) or single photon emission computed tomography (SPECT) scans lie in fNIRS’ ease of use, cost effectiveness and high temporal resolution. FMRI and PET create higher spatial-resolution brain maps of nerve cell activity, but fNIRS is by far the least invasive. This may be an especially important consideration for brain-injured patients who may not be able to tolerate the claustrophobic conditions of an fMRI or its noise, or who have trouble with motor coordination and holding still for multiple scans. With fNIRS, the infrared lights are attached to a swimming cap that is placed on the patient’s head. The patient is unconstrained and can sit comfortably in an environment that’s familiar. The device is portable, tolerates movement, and can be easily incorporated into the rehabilitation setting. It’s also a more cost-effective option for rehabilitation clinics. While an fMRI is a multimillion-dollar investment, fNIRS costs a fraction of that and has no run-time costs.

IMPACT ON TREATMENT

To date, therapists have had little evidence-based information available about the physiological changes produced at the brain level by specific interventions. They typically assess brain injury by measuring its impact on a person’s distraction and structure tolerance, and ability to perform certain skills, such as buttoning a shirt or identifying words. Based on these observations, they recommend a treatment plan that incorporates the patient’s interests and goals, and then regularly monitor progress.

Therapists at Pate Rehabilitation are among the first in the nation to use fNIRS to better understand the brain’s neuroplasticity. By looking at activation patterns and how the brain responds to tasks, they hope to gain insight on how the brain reorganizes itself after injury and which type of treatment may be most effective for improving brain recovery.

Preliminary results have led to a surprising re-evaluation of what was known about impulse control. Patients with TBI are often unable to inhibit automatic responses because of damage to the frontal area. In order to gauge attention-capability, therapists frequently administer a Stroop test to brain-injured patients, in which they are asked to identify the color of ink of the printed word, not the word itself. The patient has to focus and override the impulse to do what comes naturally and, instead, perform a less habitual response. Pate Rehabilitation researchers using fNIRS fully expected to see less activation in the part of the brain controlling behavior. Instead, they found just the opposite: There was as much activity during the simple word-reading phase as there was during the more complex color-naming phase, suggesting that the patients had significant difficulty focusing on relevant aspects of the task.

The findings beg us to reconsider traditional approaches to improving concentration. So rather than trying to boost activation levels in brain-injured patients, therapists might consider treatments to lower stimulation levels.

Having hard data at our disposal will help us be more objective and effective in our evaluation of brain injury and lead the way to better treatments. And it may one day give hope to survivors of brain injury and their families.

Patrick Plenger, Ph.D., is a board-certified clinical neuropsychologist with more than 30 years’ experience in assessments, treatments and directing brain-injury rehabilitation programs. He is currently the director of clinical research at Pate Rehabilitation.


Matthew Cloud is a doctoral student in biomedical engineering at the University of Texas at Arlington and a research assistant with Pate Rehabilitation. Having gone through rehabilitation due to a transient ischemic attack and spinal cord injuries, he has a thorough understanding of the effects of TBI and stroke.

(Editor’s note: This article from a past issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)

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