I’m a big fan of country music. After all, I was a graduate student in Music City: Nashville. I used to ride my bike down to 16th Avenue by the original Country Music Hall of Fame and listen to the up-and-coming singers perform on the street. During the late 1980s, just as I was finishing my dissertation, the biggest country star was Randy Travis. His debut album, Storms of Life, appeared in 1986, and for the next several years he dominated the country music scene.
I recently listened to Travis’s 2019 autobiography, Forever and Ever, Amen. It tells the story of his glory years, but also covers his troubled youth, his time as the singing cook at the Nashville Palace nightclub, and his tragic health problems.
In 2013 Travis was incapacitated by a massive stroke. The most common type of stroke occurs when a clot blocks the flow of blood to part of the brain. Stroke is ranked as the fifth leading cause of death in the United States; every four minutes someone dies of a stroke. Many of those that survive have brain damage. Following his stroke, Travis suffered from limited use of his right hand and severe speech impairment.
The question for readers of Intermediate Physics for Medicine and Biology is, how can physics address stroke? Two applications that are important for stroke diagnosis and treatment are Diffusion Tensor Imaging and Transcranial Magnetic Stimulation. In diffusion tensor imaging, diffusion in the brain is measured using strong gradient magnetic fields applied during magnetic resonance imaging. Diffusion is anisotropic in the brain’s white matter, with water diffusing faster parallel to nerve axon tracts than perpendicular to them. In IPMB, Russ Hobbie and I write
Diffusion is usually greater along the direction of the nerve or muscle fibers. Since the orientation of the fibers changes throughout the body, the elements of the diffusion tensor vary as well. However, some features of the diffusion tensor, such as the trace (see Prob. 49), are independent of the fiber direction, and are particularly useful when monitoring diffusion in anisotropic tissue, such as the white matter of the brain. In addition, the diffusion tensor contains information about the fiber direction, allowing one to map fiber tract trajectories noninvasively using MRI (Basser et al. 2000).
Diffusion can serve as a biomarker to diagnose stroke and to monitor recovery.
Transcranial magnetic stimulation (TMS) is a method to excite neurons in the brain. Russ and I describe it as
Magnetic stimulation can be used to diagnose central nervous system diseases that slow the conduction velocity in motor nerves without changing the conduction velocity in sensory nerves (Hallett and Cohen 1989). It could be used to monitor motor nerves during spinal cord surgery, and to map motor brain function. Because TMS is noninvasive and nearly painless, it can be used to study learning and plasticity (changes in brain organization over time; Wassermannet al. 2008). Recently, researchers have suggested that repetitive TMS might be useful for treating disorders such as depression (O’Reardon et al. 2007) and Alzheimer’s disease (Freitas et al. 2011).
You could add stroke to the list of disorders that might benefit from repetitive transcranial magnetic stimulation. I say “might” because the technique is still being studied as a stroke therapy, but any method that influences brain plasticity has at least the potential to be useful to stroke victims.
Now, almost ten years after his stroke, Travis continues to slowly recover. Although he has not yet been able to return to a singing career, in 2016 he did lead his fans in singing Amazing Grace when he was inducted into the Country Music Hall of Fame. His autobiography is captivating and inspiring. The courage and tenacity of stroke victims should motivate us all to use our science to address this devastating illness.
Originally published at http://hobbieroth.blogspot.com.