The Science of Yoga

trouble, arm and leg weakness, and sudden falls—but by definition had little to do with language and conscious thinking. However, because strokes of the rear brain can severely damage the regulatory machinery that governs life basics, they can also result in collapse and death. Even so, the vast majority of patients survive the attack and go on to recover most functions. Unfortunately, in some cases, headaches can persist for years, along with such residual troubles as imbalance, dizziness, and difficulty in making fine movements.
    The medical world of Russell’s day worried about these kinds of strokes, including a prominent type that began in circumstances that seemed quite innocuous. At beauty salons, during shampooing, women at times would have their necks tipped too far back over the edge of a sink, reducing the flowof blood through the vertebral and basilar arteries. The risk was judged especially great among the elderly. With aging, the vertebral arteries can lose their elasticity and narrow, and the normally smooth neck bones can grow spurs. When the neck bends far backward, the bony spurs can compress or otherwise harm vessels already narrow and inelastic. In addition, the stagnant blood can turn into a small factory of clot production. When the neck returns to a more normal position and the flow of blood resumes, the clots can travel down the arteries, heading deeper into the brain before settling in a narrow vessel and blocking its flow. A small epidemic of strokes resulted in a diagnosis known as the beauty-parlor syndrome.
    Russell warned of yoga dangers in the pages of the British Medical Journal , a mainstay of the field established in 1840, just as Paul was finishing medical school in Calcutta. He drew parallels between yoga and such recognized threats as the beauty-parlor syndrome, noting that some poses produce “extreme degrees of neck flexion and extension and rotation.” He specifically cited the Shoulder Stand and the Cobra, displaying a good understanding of the field. In the Cobra, or Bhujangasana, “serpent” in Sanskrit, a student lies facedown and slowly rises off the floor, pushing the trunk upward with the arms and extending the head and spine backward. Iyengar, in Light on Yoga , suggests that the head should arch “as far back as possible.” Photos show him doing just that, his head thrown back on a trajectory toward his buttocks—in other words, the kind of maneuver that Russell found worrisome.

    Cobra, Bhujangasana
    In the Shoulder Stand,the neck is bent in exactly the opposite direction, going far forward, with the chin deep in the chest, the trunk and head forming a right angle. “The body should be in one straight line,” Iyengar emphasized, “perpendicular to the floor.” Ever the enthusiast, he called the pose “one of the greatest boons conferred on humanity by our ancient sages.”
    Where Iyengar saw benefits, Russell saw danger. The postures, he said, “must for some people be hazardous.” His choice of the word “must” betrayed the speculative nature of his worry—but one grounded in a lifetime of experience. Russell warned that the basilar artery syndrome could strike practitioners of yoga and went on to cite a shadowy complication—doctors might have a hard time discerning its origin. The cerebral damage, he wrote, “may be delayed perhaps to appear during the night following, and this delay of some hours distracts attention from the earlier precipitating factor, especially when there is a catastrophic stroke.” In that case, of course, the deceased could give no account of prior activities.
    His caution went to the inherent difficulty of understanding the cause of invisible brain injuries. We typically think of illness as focused on a particular body part—such as the heart or lungs. But the origins of strokes often lie relatively far away from where they hit, starting in the wilds of the bloodstream and ending in the brain. The gap, moreover, could involve not only distance but time—hours and sometimes days—as a clot worked its way downstream or as a damaged artery slowly became swollen and gradually reduced the flow of blood. Such complicating factors meant that, for a large percentage of strokes, physicians could discover no obvious explanation. Their medical term for such injuries was cryptogenic, meaning their origin remained a mystery.
    That kind of uncertainty had long obscured the cause and the extent of the beauty-parlor syndrome. In