january 2017
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in particular the specific sensory organ known as the cochlea; this is what is known as presbyacusis, a hearing condition that can generally be resolved through the use of prosthetics or hearing aids. There is, though, also another very common but less familiar cause of hearing
Evolution
loss in adults: the condition known as otosclerosis.
result in total deafness. The abnormal bony growths typically begin to form after puberty, although to begin with they do not affect the structures involved in the hearing mechanism and do not cause any discomfort, or give rise to a loss of hearing so slight that it goes unnoticed. The earliest symptoms therefore typically emerge later, at the age of between 20 and 40 years, and generally progress slowly. If the abnormal growth of the bone continues, though, this may give rise to complete deafness in adulthood. Diagnosis is relatively simple, since specialists typically consider this condition in the event of any loss in hearing capacity in an adult patient. Different tests are generally employed, both to rule out other conditions and to identify the lesions characteristic of otosclerosis. This will normally involve a number of studies, from hearing tests to tympanometry to assess the mobility of the tympanum, and even imaging studies such as computed tomography. In each case the specialist will select the most appropriate tests, and once the specific study has been performed, the problem will be easy to classify. As for treatment, there are no effective pharmacological solutions to the problem or to prevent its development. If the otosclerosis causes only a slight or moderate loss in hearing, then hearing aids may be used, although this does not resolve the underlying problem or prevent the evolution of the condition. As a result, if the hearing loss has become significant, the only option is surgery. Fortunately, these days this is an operation that could be classified as both simple and effective, and in most cases will restore the patient’s hearing.
Frequency and causes
Otosclerosis is a very common disorder, estimated to affect nearly 1.5% of the population. What is more, extensive studies based on autopsies have revealed that some 8% of the population have alterations connected with the condition, although in most cases they have not evolved significantly to give rise to symptoms, or any other problems or evidence of their existence. The condition comprises the growth of an abnormal node of bone tissue in the otic capsule, the bony housing that surrounds the inner ear, where the sensory organ is located. As it grows, this abnormal bony growth progressively covers over the ossicle that serves as the bridge between the middle and inner ear, the stirrup, fixing it in place and preventing it from transmitting vibrations. As a result, although the tympanum will vibrate and the other middle ear bones move, the stirrup remains immobile, fixed to the osic capsule of the inner ear. This results in a loss of hearing and progressively severe deafness. At later stages, if the abnormal overgrowth also affects the inner ear, this can give rise to other symptoms, such as tinnitus or buzzing, and even episodes of dizziness. The precise origin of the condition has not been fully established, although we know that it may be the result of various causes, and in many cases is connected with hereditary genetic factors. It is therefore common for the disorder to be found in several members of the same family. It is also more likely to affect women than it is men.
The evolution of the condition will vary, but in many cases over time it can completely prevent hearing in the affected ear. And as in 85% of cases the disorder occurs in both ears, although not always to the same degree, it can often
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