The Science of Yoga

was a resident. The doctors saw many indications of stroke and, in their report, noted the similarity of the man’s symptoms to those of Nagler’s female patient. The man could feel little sensation on the right side of his body. His eyeballs twitched. His left arm and leg were weak, had poor coordination, and showed a prominent tremor when he tried to reach for something or move his hand or foot to a precise location.
    During the physical examination, the doctors noticed on the man’s back a series of bruises. The bluish discolorations ran down his lower neck across the C5, C6, and C7 vertebrae. Apparently, the team wrote in the Archives of Neurology , “these resulted from repeated contact with the hard floor surface on which he did yoga exercises.” The bruises, the doctors added, were a sign of neck trauma.
    Hanus focused on assessing the inner damage. Diagnostic tests revealed blockages of the left vertebral artery between the C2 and C3 vertebrae. The team found that the blood vessel there had suffered “total or nearly complete occlusion.”
    During the man’s first week in the hospital, the left side of his face developed Horner’s syndrome—the constricted pupil and drooping eyelid. Slowly, he regained his ability to walk, though his gait remained clumsy. Two months after his attack, and after much physical therapy, the man was able to walk with a cane. But the team reported that he “continued to have pronounced difficulty in performing fine movements with his left hand.”
    Hanus and his team concluded that the young man’s situation was no anomaly or medical oddity but instead a new kind of danger. Healthy individuals can seriously damage their vertebral arteries, they warned, “by neck movements that exceed physiological tolerance.” And yoga, they stressed, “should be considered as a possible precipitating event.” In its report, the Northwestern team cited not only Nagler’s account of his female patient but Russell’s early warning. The concern was beginning to ripple through the world of medicine.
    The next case showed its global spread. In Hong Kong, a woman of thirty-four practiced yoga faithfully. One day, shortly after doing a Headstand for five minutes, she developed a sharp pain in her neck and numbness in her righthand. A surgeon made an incorrect diagnosis and prescribed neck traction and physical therapy. Her symptoms got worse. The attacks of nausea and dizziness grew in severity. Eventually her troubles came to the attention of a medical team at the University of Hong Kong and Queen Mary Hospital.
    By this point—some two months after the neck pain—the doctors found that the woman showed signs of disorientation and paralysis on the left side of her body, as well as an inability to feel sensations of touch. Her eyes displayed the jerky movements typical of a rear-brain stroke, and the physicians made that the provisional diagnosis.
    The doctors repeatedly scanned the woman’s brain with imaging devices over the next few days. But they found nothing, even as her consciousness began to ebb. Finally, the team located a region of tissue that appeared dead from lack of blood. It ranged over the pons, the thalamus, and the occipital lobe. The doctors sought to pinpoint the cause of the stroke by injecting dye into the woman’s neck arteries and taking X-rays. The diagnostic images showed no problems in the vertebral arteries but a severe blockage in the basilar artery.
    The doctors had put the woman on blood thinners and clot-dissolving drugs after the provisional diagnosis. Eventually she underwent intensive physical therapy as well. After a year, she regained strength on the left side of her body. But she still exhibited clumsiness in her left hand.
    Jason K. Y. Fong, a young neurologist, led the analysis. In 1993, he and his colleagues reported that the woman’s problems had probably begun when vertebral arteries in the C1–C2 region suffered a tear or a severe reduction in blood flow. That produced a clot, the doctors wrote in Clinical and Experimental Neurology , that eventually worked its way into the basilar artery and blocked the blood supply to her inner brain. They attributed the lack of visible damage in the vertebral artery to the likelihood that the exceptionally long period between the Headstand and the hospital admission “may have allowed sufficient time for spontaneous healing.”
    The delay in uncovering the woman’s stroke and its likely cause bore