Otosclerosis is the name for the abnormal growth of bone in the middle ear and is a common cause of hearing loss in adults. Hearing loss is usually conductive, which means it affects the small bones of the middle ear that conduct sound to the inner ear. Sensory nerve damage and deafness can also manifest. Due to the lack of objective symptoms, doctors often say that this is a disease in which the patient cannot hear anything and the doctor cannot see anything.
Otosclerosis is not associated with atherosclerosis and is not typical for old age.
How do we hear?
Listening is a series of events in which the ear converts sound waves into electrical signals and causes nerve impulses that are sent to the brain where they are interpreted as sound. The organ of hearing, the ear, has three main parts: outer, middle and inner ear. Sound waves enter through the outer ear to the eardrum, which is the border with the middle ear, causing its oscillation. The vibrations are transmitted to the three ossicles (malleus, incus and stapes). The plate of the stapes is attached to the oval membrane that is injected into fluid-filled inner ear. Fluid movements stimulate hearing cells in the cochlea of the inner ear and cause the formation of nerve impulses. The pulses are transmitted to the brain where they are recognized as sound. Different sounds stimulate different hearing cells in the cochlea and brain can distinguish sounds.
How otosclerosis damages your hearing?
Otosclerosis can cause different types of hearing loss, depending on the structures affected by the disease. Otosclerosis usually affects the last bone in the chain, stapes, which is inserted into an oval membrane. Abnormal growth of spongy bone (which is why the disease is sometimes called otospongiosis) attaches stapes to the oval frame, preventing it from moving and sounds are not implemented in the inner ear. Because it is impossible to conduct sound, this type of hearing loss also called conductive hearing loss. Rarely, otosclerosis causes nerve damage and sensorineural hearing loss occurs.
Otosclerosis Cause
The cause of otosclerosis is not entirely clear. It is known to occur more frequently in some families, that there is a tendency to be inherited. It has been calculated that the person whose one parent has otosclerosis there is a 25% probability that they will catch themselves. If both parents have otosclerosis, the probability increases to 50%. Genetic cause of otosclerosis has not been found and it is assumed that there are more genetic causes, as well as non-genetically caused otosclerosis. Most popular is the theory that there is a dominant gene for otosclerosis, however it is not fully active or not developed in every generation. People in the same family who have otosclerosis usually have similar symptoms: disease begins in a similar age and progresses at a similar rate. Different families differ in those aspects.
The bones in our body are constantly destroyed and rebuilt. In otosclerosis recovery is apparently disturbed, not normally producing new tissue, resulting in accumulation of spongy bone.
Research shows that white women and of middle age are most at risk. Research has also shown a correlation between otosclerosis and the hormonal changes in pregnancy because the disease often reveals itself or worsens during pregnancy and after childbirth. There is some evidence of a connection between viral infections (measles) and otosclerosis.
Otosclerosis Frequency
At the age of 30-50 years, 10-18% of white women and 7-9% of white men have histological signs of otosclerosis. Less than 10% of them seek medical treatment for hearing loss (i.e. 1-2% of these women and less than 1% of the men). Among the black population only 1% had histological signs of otosclerosis and the incidence of clinical hearing loss is considerably lower.
Development of disease
The first sign of otosclerosis is the growth of small amounts of spongy tissue in front of the oval frame which divides middle and inner ear. This process can begin in late childhood or adolescence. At the beginning, this tissue has many small blood vessels and can grow rapidly. Later it becomes hard, sclerotic. Conductive hearing loss occurs when bone tissue grows around the ossicles and prevents their movement. Ordinary bone tissue from the front oval membrane overgrow the stapes and attaches it to the oval membrane. If the otosclerotic tissue doesn’t cover the small bones, illness is said to have ‘subclinical’ progress and the person can be without symptoms for years. The term ‘histological otosclerosis’ indicates the existence otosclerotic tissue, regardless of whether it causes symptoms or not. ‘Clinical’ otosclerosis is a name is used when the symptoms are present: it can be present from the early age, but very rarely begins before the age of 50. In the beginning, the earing loss only affects low frequencies. It may be the same for years and then suddenly worsen. Hearing loss is usually bilateral. It rarely manifests in one ear; soon the symptoms occur in the other ear.
Otosclerosis Symptoms
Hearing loss is the most common symptom. Hearing loss is usually bilateral and initially of conductive character. It develops gradually with age, but it can worsen and develop rapidly. Many patients first notice that they can not hear low-pitched sounds or that you no longer hear whispering.
In addition to hearing loss other possible symptoms are dizziness, balance disorders and tinnitus. Tinnitus is a feeling of noise, ringing, buzzing or hissing in the ears or head that accompanies many forms of hearing loss. Tinnitus and balance disorders may eventually stop.
Sensory, perceptual hearing loss can also start, especially for high frequencies. Name ‘cochlear otosclerosis ‘ refers to the sensory hearing loss. It can occur because of impaired blood flow or enzyme that produces otosclerotic tissue, and is rarely caused by abnormal growth of tissue in the inner ear. Sensory hearing loss rarely occurs without the conductive loss.
In advanced stages of the disease problems result due to loss of auditory communication with the environment, and sometimes due to psychological changes.
Otosclerosis Diagnosis
The diagnosis is set by physician specialists for diseases of the ear, nose and throat: otolaryngologist. After discussion with the patient an examination of the outer ear and the specific examinations are conducted; audiogram and tympanogram by which sensitivity and conductive function of the ear are analyzed.
Otosclerosis Treatment
As the cause is not known, there is no causal but only symptomatic treatment. Success can be achieved only by surgery. The surgery is called a stapedectomy, and the affected bone is compensated by a prosthesis. It is required to discuss the possible risks and complications with the surgeon beforehand. In rare cases, surgery can worsen the hearing.
If it is a moderate hearing loss, surgery may not be the treatment of choice. Improvement can be achieved by hearing aids that are placed after consultation with a physician.
Treatment wih fluoride can be attempted with damages of the inner ear. Fluoride is given in daily doses of 3-50 mg over three months. In this way it sometimes inactivates neurological diseases and prevent further progress of the process.
Otosclerosis research
Currently, the researchers engaged in understanding of disease manifestation, for example. by detecting genes that cause otosclerosis. Long studies have dealt with the assessment of the efficiency of the laser, which have recently been used in surgery, means to amplify sound and studying different types of prostheses. Develop of new diagnostic possibilities are also explored as well.