After former President Gerald Ford suffered one or possibly two mild strokes while attending the Republican National Convention last week, his doctors quickly predicted a full recovery. But his illness raised a troubling question: How could a team of specially trained physicians initially misdiagnose a stroke, especially in a former President, who, one assumes, always receives the very best medical care? The answer, unfortunately, is quite easy. Strokes are often misdiagnosed, even by excellent doctors, for a simple reason. Many symptoms commonly linked with stroke are also seen in other illnesses.
Take, for example, Ford's shaky balance. Onlookers noticed it as...