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The trio of bone detectives Lloyd Minor, George T. Nager and John Carey
The trio of bone detectives—Lloyd Minor, George T. Nager and John Carey—linked tiny perforations or thin sections in temporal bones (left) to a rare disorder in which loud noises cause sudden dizziness.


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The Clue in the Old Bones

Pack rats who spend their lives taking abuse for never throwing anything away can take solace in knowing that just such habits made possible a recent medical advance here. A nearly forgotten cache of more than 1,000 temporal bones amassed over a period of some 30 years presented otolaryngologists with the data they needed to understand the basis for a strange condition in which people are stricken with dizziness after hearing loud noises.

The collection that helped solve the mysterious disorder—known as superior canal dehiscence syndrome (or simply SCDS)—had been gathered from cadavers starting in the 1930s. The person who meticulously kept it up and refused to get rid of so much as a single sample was George T. Nager, M.D., chairman of otolaryngology between 1970 and 1984. For awhile after Nager stepped down, students and professors continued using the collection, but during the ’80s and ’90s the bones were put into storage and forgotten. And there they might have remained if it hadn’t been for Lloyd Minor, M.D., and his colleagues at Hopkins’ Hearing and Balance Center, who were trying to get to the roots of the bizarre dizziness disorder.

Descriptions of a syndrome similar to the one that Minor was studying can be traced back to the turn of the century with the work of the Italian biologist Pietro Tullio. Tullio, who laid the foundation for our understanding of the vestibular system, learned about the sense of equilibrium by drilling holes in the balance canals of pigeons. Afterward, he found, the birds displayed involuntary eye movements following loud noises, evidence that the balance canal and eye and head movements were related. At just about the same time, several physicians reported they had observed similar eye movements in neurosyphillis patients whose bones around the balance canal had been eaten away by infection. Symptoms of sound-induced vertigo thus became known as “Tullio’s phenomenon.” But still, no one linked the disorder to the holes in the canals.

Enter Minor, who in his years as an otolaryngologist had treated several patients who’d been stricken by severe vertigo after they heard loud music, spent an afternoon in a noisy sports stadium or even listened to the dial tone of a telephone. Then, on a spring day three years ago, a young male patient told the otolaryngologist that stationary objects began moving dizzily back and forth every time he sang in the shower. Minor had done a lot of research demonstrating the relationship between balance canals and eye movement in people, so he quickly performed eye tests on the patient. He found that tones played in the man’s ear stimulated the same circular and upward eye motions as those from stimulation to the top balance canal. The researchers took a look at the balance canal via a special CT scan, and—voila—they found a tiny hole in the temporal bone.

That’s when Nager’s cache became vital. Suspecting that the hole was related to the patient’s dizziness, Minor called on the former chairman for help in locating and analyzing the horde of temporal bones. Nager dug them out of storage and spent six months last year with Minor and postdoctoral fellow John Carey, M.D., scrutinizing the specimens one by one for holes. Eventually they located five with the same kind of tiny perforation Minor had found in his patient. Fourteen others had thin sections in the canals. “We found that if the temporal bone in one ear was thin, the second ear showed the same thinness,” an indication that the flaw is likely to be a developmental problem, Minor says. With such thinning any disruption to the canal—an accidental head trauma, for instance—makes it respond abnormally to loud noises.

So what difference does this new understanding make? The fact is that until now people with SCDS have gone without help, been misdiagnosed or even been referred to psychiatrists. Now, doctors will be able to offer a range of treatments for the rare dizziness disorder—from simple lifestyle adjustments, like wearing ear plugs, to surgery, depending on the severity of the case. Minor’s surgical approach is to plug the hole or cover it with a mixture of muscle tissue and bone dust, which hardens to seal the canal and ease symptoms or eliminate them altogether. Meanwhile, his team is studying a chinchilla with the condition to come up with even better treatments.



—- Jim Duffy



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