The Science of Yoga

experiencing a number of physical disorders. She could feel no sensations on the right side of her body. Her left arm and leg wavered. Her eyes kept glancing involuntarily to the left. And the left side of her face showed a contracted pupil, a drooping upper eyelid, and a rising lower lid—a cluster of symptoms known asHorner’s syndrome. Nagler reported that the woman also had a tendency to fall to the left.
    Diagnostic inquiry showed that her left vertebral artery had narrowed considerably between cervical vertebrae C1 and C2, revealing the probable site of the blockage that resulted in the stroke. It also showed that the arteries feeding her cerebellum (the structure of the rear brain that coordinates the muscles and balance) had undergone severe displacement, hinting at trouble within. Given the day’s lack of advanced imaging technologies, an exploratory operation was deemed necessary to better evaluate the woman’s injuries and prospects for recovery.
    The surgeons who opened her skull found that the left hemisphere of her cerebellum had suffered a major failure of blood supply that resulted in much dead tissue. They also found the site seeped in secondary hemorrhages, or bleeding. In response, the physicians put the woman on an extensive program of rehabilitation. Two years later, she was able to walk, Nagler reported, “with broad-based gait.” But her left arm continued to wander and her left eye continued to show Horner’s syndrome.
    Nagler concluded that such injuries appeared to be rare but served as a warning about the hazards of “forceful hyperextension of the neck.” He urged health professionals to show caution in recommending such difficult postures to individuals of middle age.
    The next case came to light in 1977. The man of twenty-five had been in excellent health and doing yoga every morning for a year and a half. His routine included spinal twists in which he rotated his head far to the left and far to the right. Then, according to a team in Chicago at the Northwestern University Medical School, he would do a Shoulder Stand with his neck “maximally flexed against the bare floor,” echoing Iyengar’s call for perpendicularity in Light on Yoga. The team said the young man usually remained in the inversion for about five minutes.
    One morning upon finishing this routine, he suddenly felt a sensation of pins and needles on the left side of his face. Fifteen minutes later, he felt dizzy and his vision blurred. Soon, he was unable to walk without assistance and had trouble controlling the left side of his body. The man also found it difficult to swallow. He was rushed to the hospital.
    Steven H. Hanus was a medical student at Northwestern who became fascinated by the case. He took the lead and worked with the chairman of the department ofneurology to elucidate the exact cause of the disabilities, publishing a study with two colleagues when he 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