Circulation: The Great Brain Robbery

Doctors have long been as puzzled as their patients have been alarmed when some unaccustomed exercise causes not only numbness in an arm but faintness and even temporary blindness. Now artery researchers at West Virginia University School of Medicine have an explanation for what investigators call "the subclavian-steal syndrome."

As Irish-born Dr. Robert James Marshall explained it last week to the American Heart Association in Atlantic City, the steal involves one of the arteries that normally help to supply blood to the brain. Besides the well-publicized carotid arteries, there are two lesser-known vertebral arteries, each of which branches off from...