Symptom: Dizziness. Cause: Often Baffling. - New York Times: "When he lectures other doctors, Dr. Olshaker said, he tells them: 'You hate this topic. Dizziness is associated with nausea, fear, anxiety and frustration - and that's in the physician. Never mind the patient!'
Even when the cause is probably not serious, doctors generally are cautious, ordering a number of tests and sometimes consulting with neurologists to make sure the cause of the vertigo is not life-threatening. "The diagnosis and treatment of vertigo have markedly improved in the last two decades. The cause of most benign positional vertigo is now believed to be calcium debris that has dislodged from a part of the inner ear and strayed into one of the fluid-filled semicircular canals of the sensitive vestibular system.

The system is a cluster of structures that keeps the brain updated on the body's orientation and movement in space.

These microscopic flecks of calcium debris do not in themselves lead to problems, but sometimes in their meandering they brush against delicate, hairlike cells, sending misinformation to the brain.

When those signals conflict with more accurate signals from other nerves, the brain responds with disorientation and vertigo.

The three semicircular canals of the inner ear loop out - more or less at right angles, like three edges of a box meeting at the corner - from a chamber called the vestibule.

The slight fluid movements in these canals in response to head movements and gravity activate the hair-trigger cells that relay positional information to the brain.

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Inside the vestibule, scores of tiny "stones" called otoliths are attached to a membrane, and when the head turns in any direction, the slight force imparted to the otoliths is translated into nerve messages about motion and orientation.

The road to benign positional vertigo starts when some of the otoliths, or fragments of them, come loose from the membrane and go rafting in the endolymph, the fluid inside the tiny canals.

They tend to settle by gravity in the rearmost canal, which loops down and up like the debris trap under a sink.

A variety of things can set the "ear rocks," as they're also known, to wandering: blows to the head or sudden movements (roller coasters can have this effect), and perhaps most often, simply the wear and tear of aging on the balance organs.

It may be hard to identify the cause of a particular episode, and for many people the first time they have symptoms is waking up in the morning or rolling over in bed.

Dr. Fitzgerald, who says he has treated more than 2,000 cases of benign paroxysmal positional vertigo in the last 15 years, confirmed the diagnosis. He then performed what has become accepted as the definitive treatment, a series of head gyrations called the Epley maneuvers.

The maneuvers involve moving the head into four different positions sequentially, taking advantage of gravity to roll the calcium flecks out of the sensitive part of the canal to a place where they cause less trouble.

In cases like Mr. Farquhar, the Epley maneuvers are repeated, the patient sits up, and the treatment is complete. For the next 48 hours, Mr. Farquhar was cautioned to avoid a variety of movements that could send the debris tumbling back into the canal.

"Most doctors who do this say that 80 percent of patients have their symptoms alleviated in one set of treatments," Dr. Fitzgerald says.