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.
