Otosclerosis
| Otosclerosis | |
|---|---|
 |
|
| Chain of ossicles and their ligaments. (Stapes visible near center right.) | |
| Classification and external resources | |
| Specialty | otolaryngology |
| ICD-10 | H80 |
| ICD-9-CM | 387 |
| OMIM | 166800 605727 |
| DiseasesDB | 29289 |
| MedlinePlus | 001036 |
| eMedicine | article/994891 article/859760 |
| Patient UK | Otosclerosis |
| MeSH | D010040 |
Otosclerosis or otospongiosis is an abnormal growth of bone near the middle ear. It can result in hearing loss. The term otosclerosis is something of a misnomer. Much of the clinical course is characterised by lucent rather than sclerotic bony changes, hence it is also known as otospongiosis.
This is an inherited disease. The primary form of hearing loss in otosclerosis is conductive hearing loss (CHL) whereby sounds reach the ear drum but are incompletely transferred via the ossicular chain in the middle ear, and thus partly fail to reach the inner ear (cochlea). This usually will begin in one ear but will eventually affect both ears with a variable course. On audiometry, the hearing loss is characteristically low-frequency, with higher frequencies being affected later.
Sensorineural hearing loss (SNHL) has also been noted in patients with otosclerosis; this is usually a high-frequency loss, and usually manifests late in the disease. The causal link between otosclerosis and SNHL remains controversial. Over the past century, leading otologists and neurotologic researchers have argued whether the finding of SNHL late in the course of otosclerosis is due to otosclerosis or simply to typical presbycusis.
Most patients with otosclerosis notice tinnitus (head noise) to some degree. The amount of tinnitus is not necessarily related to the degree or type of hearing impairment. Tinnitus develops due to irritation of the delicate nerve endings in the inner ear. Since the nerve carries sound, this irritation is manifested as ringing, roaring or buzzing. It is usually worse when the patient is fatigued, nervous or in a quiet environment.
It may be that a genetic tendency to develop otosclerosis is inherited by some people. Then a trigger, such as a viral infection (like measles), actually causes the condition to develop.
The disease can be considered to be hereditary, but its penetrance and the degree of expression is so highly variable that it may be difficult to detect an inheritance pattern. Most of the implicated genes are transmitted in an autosomal dominant fashion. One genome-wide analysis associates otosclerosis with variation in RELN gene.
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Wikipedia