Description, Causes and Risk Factors:
Otosclerosis means hardening of one of the bones of the ear. Otosclerosis is an uncommon disease and typically presents in young patients, with a 2:1 f:m ratio. It is bilateral in up to 85% of patients, but often asymmetric. The disease occurs most frequently between 30 years and 50 years of age and is known to worsen during pregnancy.
The etiology remains unknown, although an in?ammatory response may be responsible. The condition may also be inherited. Two patterns of disease exist. The more common fenestral form, seen as abnormal hypo dense or sclerotic bone involving the ?ssula ante fenestram produces conductive hearing loss, and is owing to ?xation of the stapes footplate at the level of the oval window, with a hearing loss of up to 50-60 dB. The retrofenestral or cochlear form is less common and is often seen in association with the fenestral variety. A mixed conductive and sensorineural hearing loss is seen in cochlear otosclerosis, although pure sensorineural hearing loss may occur. Vestibular symptoms with unsteadiness and episodes of vertigo may also occur in this form of the disease.
Measles virus RNA is found in otosclerotic foci in footplates removed during surgery. Measles virus infection may activate the gene responsible for otosclerosis. Otosclerosis, however, is not responsible for all cases of stapes ankylosis. A heterogeneous group of disorders, including other bone degenerative disorders, appears to cause stapes fixation and conductive hearing loss.
Over the past century, leading Neurologist &otologists researchers have argued whether the finding of SNHL late in the course of otosclerosis is due to otosclerosis or simply to typical presbycusis. There are certainly a few well documented instances of sclerotic lesions directly obliterating sensory structures within the cochlea and spiral ligament, which have been photographed and reported. Other supporting data includes a consistent loss of cochlear hair cells in patients with otosclerosis; these cells being the chief sensory organs of sound reception. A suggested mechanism for this is the release of hydrolytic enzymes into the inner ear structures by the spongiotic lesions.
Progressive hearing loss is the most typical symptom of the stapedial-type of otosclerosis. In pure cochlear otosclerosis a sensorineural hearing loss is the main finding. The hearing loss appears to be accelerated by pregnancy. In addition to a hearing loss, some patients experience dizziness or unsteadiness. It is more like disequilibrium and not usually vertigo. Often the dizziness or disequilibrium disappears after a stapes operation. Most patients with otosclerosis also notice tinnitus (ringing in the ears or ear noise) to some degree. Tinnitus develops due to changes in the hearing pathway. It is usually more apparent when the patient is fatigued, nervous, or in a quiet environment. The amount of tinnitus is not necessarily related to the degree of hearing impairment.
Cochlear otosclerosis should be considered inpatients with sensorineural or mixed hearing loss,when MRI ?ndings of perilabyrinthine and pericochlear soft tissue with contrast enhancement,together with increased signal in T2-weightedimages, are seen. High-resolution computed tomography (HRCT) should then be performed to con?rm the diagnosis and exclude otherconditions that demonstrate similar ?ndings onMRI.
There are several treatment options for cochlear otosclerosis. Use of a hearing aid in patients with asymmetrical hearing loss is often suf?cient. In patients with conductive hearing loss and concurrent fenestral otosclerosis, stapedectomy and use of a prosthesis help to restore hearing. Sodium ?uoride or chelating agents may also be used to promote re-mineralization of the otosclerotic plaques.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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