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Innovative Surgery on the Ear Bone Relieves Rare Form of Severe Dizziness and Hearing Loss
Lloyd B. Minor, M.D.
Researchers supported by NIDCD have shown that the symptoms that accompany superior canal dehiscence, a rare hearing and balance disorder, can be treated successfully by a single operation that plugs up a thinning layer of bone in the inner ear. In what is believed to be the largest follow-up analysis of patients after their surgery for the syndrome, a team of researchers from the Johns Hopkins University Department of Otolaryngology--Head and Neck Surgery, led by Lloyd B. Minor, M.D., found that plugging the superior canal where the bone casing is thin, and then covering the plug with a bone graft, prevented symptoms from recurring.
“The surgical plugging procedure can put a stop to even severe symptoms and can lead to normal daily activities and, in some cases, to a mild-to-moderate improvement in hearing,” says Dr. Minor, who, in 1995, first clinically described superior canal dehiscence and subsequently developed the surgical techniques to repair it.
Superior canal dehiscence is a rare and debilitating disorder marked by an array of disturbing symptoms, such as sudden dizziness; loss of balance; rapid, uncontrollable eye movements; falling down after a loud noise; and hearing loss. Superior canal dehiscence occurs in roughly equal numbers of men and women and is often not diagnosed until after age 40, when symptoms, such as hearing loss, appear to worsen. However, patients often recall that initial symptoms occurred much earlier in their lives.
The researchers say that the plugging procedure, which essentially compresses and closes off the canal, may help restore the hearing of patients who already have experienced some hearing loss from the syndrome. The researchers observed that improvements in hearing occurred in five of 29 patients who underwent surgery for the disorder from 1996 to 2005.
No wider than a toothpick, the canal bone rests at the top of the inner ear’s three semicircular canals. Thinning due to failure of bone to develop properly and maintain strength over time makes the ear hypersensitive to sound and motion. A common complaint is autophony, where patients hear their own voice reverberating inside their head. For some patients, even a conversational level of loudness can produce symptoms strong enough to cause severe discomfort.
Although research on the condition is relatively new, Minor believes the underlying cause of the syndrome is an opening in a layer of bone that fails to develop to normal thickness during or after birth. The open canal then responds to sounds and to pressure changes from activities, such as coughing, sneezing, or straining. This abnormal activation of the canal is misinterpreted by the brain as a head movement causing patients to lose their balance and to have abnormal eye movements.
While no survey exists to indicate just how widespread this condition is, Minor says about two-thirds of those who have superior canal dehiscence never will need surgery. But for the remaining one-third who undergo surgery to repair the bone casing in the ear, the surgery in most cases fixes the disturbance in balance. In their latest findings, the researchers report that of the 19 patients with the condition who had undergone analysis of abnormal eye movements, surgery resolved each case of dizziness brought on by loud noises.
The surgery, which takes from four to six hours, is extremely delicate and requires access to the inner ear, a space the surgeons describe as no wider than the diameter of a dime. They first cut a hole above the ear and open the skull, after which they gently move aside a part of the brain so that they can reach the three paired canals. The superior canal is closest to the top of the head. The plug mixture is made up of the patient’s bone and fibrous tissue taken from the area of the incision and the temporary opening the surgeons make in the skull.
“This innovative surgery offers real hope for the victims of this debilitating syndrome” says James F. Battey Jr., M.D., Ph.D. director of NIDCD. “These studies have proven that relief is possible for those individuals who have symptoms severe enough to interfere with normal activities.”
The researchers note that only long-term information from post-surgical monitoring of patients for more than 10 years after surgery truly will confirm if the benefits of surgical treatments remain or decline at some point. Since the team saw its first patient with the condition in 1995, they have successfully operated on 39 individuals. The team plans to continue monitoring its patients.
The findings from this research were reported at the Combined Otolaryngological Spring Meeting held in Chicago, IL, on May 19–22, 2006.