My hearing started to go about the time Sharon was born and just kept getting worse each year. After two sets of hearing aids (they need to be replaced every four years or so) at $5,000 a pop, I went to see an ENT specialist who gave me a new hearing test and said all of this could be fixed with a simple operation covered by insurance. And yes, I am very unhappy that this possibility was never mentioned previously.
Otosclerosis
Otosclerosis is a bone-growth disorder that only occurs in the ear. There are two stages of the process: first the bone becomes spongy, and then it hardens. The most common place for this to occur is where the stapes connects to the cochlea (see figure 19.1). Bone growth fuses the stapes and prevents it from vibrating. Since the stapes won’t vibrate normally, sound is blocked and hearing loss results. If otosclerosis penetrates the cochlea, it can also cause sensorineural hearing loss (nerve hearing loss).
Otosclerosis is common. Autopsy studies show that about 3 percent of Americans have microscopic evidence of otosclerosis but that only one in ten of them develop hearing loss. People with hearing loss caused by otosclerosis usually have it in both ears, and it is more common in females than males.
Most people who will develop otosclerotic hearing loss begin to have symptoms between the ages of twenty and thirty, and the loss continues to progress throughout life. It is more common in Caucasians than African Americans, and is rare in Asians. Otosclerosis is autosomal dominant with variable penetrance (that is, there is variable development of disease even if the gene is inherited).
Treatment
Hearing Aids
Otosclerosis is treated with hearing aids or surgery. Oral medications are sometimes used in an effort to prevent the sensorineural component of the hearing loss from getting worse (see below). Hearing aids are a safe and effective treatment, but they have several drawbacks. First off, they are expensive. An average pair of hearing aids might cost about $5,000, and they are generally not covered by insurance. Since they are replaced every four to five years, this can add up to $50,000 or more over an adult lifetime. When you add in $100 per year for batteries you realize what a financial investment hearing aids are. Another drawback is that hearing aids only work when they are in use (for example, not during sleep or while participating in water sports), and unfortunately hearing aids carry a stigma of aging or infirmity.
Medication
Epidemiologic studies have suggested that otosclerosis is less common in areas with fluoride in the drinking water, so fluoride supplements along with calcium and vitamin D have been tried to halt the progression of otosclerosis. Results of fluoride treatment have been at best inconsistent.
Surgery
Stapedectomy is an operation lasting thirty minutes to an hour that is performed through the ear canal under local or general anesthesia, usually as an outpatient procedure. In two variations, the stapes is removed (stapedectomy) or an opening through it is made (stapedotomy).
Lasers are often used to help remove this delicate bone after which it is replaced with a stapes prosthesis. The success rates of stapedectomy and stapedotomy are the same, about 85–90 percent. Efforts to correct failed stapedectomy/stapedotomy have lower success and higher complication rates. (Middle ear reconstruction for conductive hearing loss is discussed in chapter 18.)
Figure 19.1
In otosclerosis, the stapes may be immobilized by a bone-like overgrowth and must be replaced by a prosthesis to restore hearing.
Risks and Complications
The risk of sensory hearing loss, about 1 percent, is the greatest concern to both patient and surgeon in performing stapedectomy. Twenty percent of patients experience a temporary change in taste perception because the taste nerve (chorda tympani) must frequently be moved to perform the surgery.