Otosclerosis is a disease of the bone of the otic capsule that causes an abnormal accumulation of new bone, most commonly within the oval window.
Otosclerosis is one of many genetic and acquired conditions that affect the osseous structures that cause conductive and sometimes, mixed hearing loss. Others include tympanosclerosis, Paget disease, branchio-oto-renal dysplasia, osteogenesis imperfecta, and Goldenhar syndrome.
Estimates of otosclerosis prevalence are generally low, with some reports suggesting a clinical prevalence of less than 1% (1). Some data also suggest higher prevalence rates among Hispanic and White patients compared with Black patients (2).
Rarely, hearing loss caused by otosclerosis manifests in early childhood, but most cases do not become evident until the late adolescent or early adult years, when slowly progressive, hearing loss is diagnosed. Otosclerosis typically develops in one ear, although more than half of patients continue developing symptoms in both ears (3).
General references
1. Declau F, Van Spaendonck M, Timmermans JP, et al. Prevalence of otosclerosis in an unselected series of temporal bones. Otol Neurotol. 2001;22(5):596-602. doi:10.1097/00129492-200109000-00006
2. Choi JS, Sweeney AD, Alava I, et al. Otosclerosis in an Urban Population. Otol Neurotol. 2021;42(1):24-29. doi:10.1097/MAO.0000000000002870
3. Cureoglu S, Schachern PA, Ferlito A, et al. Otosclerosis: etiopathogenesis and histopathology. Am J Otolaryngol. 2006;27(5):334-340. doi:10.1016/j.amjoto.2005.11.001
Etiology of Otosclerosis
In otosclerosis, bone is resorbed and redeposited with pathologic consequences (1). The most commonly affected area involves the stapes; as a result, the stapes becomes immobile and conductive hearing loss develops. Otosclerosis may also cause a sensorineural hearing loss, particularly when the foci of otosclerotic bone are adjacent to the scala media.
Otosclerosis typically runs in families, and half of all cases are inherited. Otosclerosis is a complex disease with multifactorial inheritance. In some cases, autosomal dominant forms are caused by multiple genes including TGFB1 (19q13.2), BMP2(20p12.3), BMP4 (14q22-q23), MEPE (4q21), and OTSC7 (6q13–16) (2, 3). Infection with the measles virus has been hypothesized to play an inciting role in patients with a genetic predisposition for otosclerosis; however, this is not universally true (4, 5).
Etiology references
1. Rudic M, Keogh I, Wagner R, et al. The pathophysiology of otosclerosis: Review of current research. Hear Res. 2015;330(Pt A):51-56. doi:10.1016/j.heares.2015.07.014
2. Rämö JT, Kiiskinen T, Seist R, et al. Genome-wide screen of otosclerosis in population biobanks: 27 loci and shared associations with skeletal structure. Nat Commun. 2023;14 (1):157. doi: 10.1038/s41467-022-32936-3
3. Thys M, Van Camp G. Genetics of otosclerosis. Otol Neurotol. 2009;30(8):1021-1032. doi:10.1097/MAO.0b013e3181a86509
4. Potocka-Bakłażec M, Sakowicz-Burkiewicz M, Kuczkowski J, et al. Expression of TNF-α, OPG, IL-1β and the presence of the measles virus RNA in the stapes of the patients with otosclerosis. Eur Arch Otorhinolaryngol. 2015;272(8):1907-1912. doi:10.1007/s00405-014-3008-4
5. Crompton M, Cadge BA, Ziff JL, et al. The Epidemiology of Otosclerosis in a British Cohort. Otol Neurotol.2019;40(1):22-30. doi:10.1097/MAO.0000000000002047
Diagnosis and Treatment of Otosclerosis
History, otoscopic examination and audiometry
Imaging (high-resolution CT)
Sometimes a hearing aid
Sometimes surgery
Otosclerosis is diagnosed primarily through history, otoscopic examination, and audiometry. High-resolution CT (HRCT) temporal bone imaging serves as a confirmatory and preoperative tool, and to rule out other concurrent conditions. There is usually a normal appearing tympanic membrane on otoscopy (1). Lucency at the fissula ante fenestram on HRCT is the hallmark imaging finding of otosclerosis (2), although its absence on CT does not exclude otosclerosis.
Otosclerosis may be treated with hearing amplification or surgical intervention (eg, stapedotomy, stapedectomy). A hearing aid may improve hearing. Alternatively, stapedotomy or stapedectomy to remove some or all of the stapes and to replace it with a prosthesis may be beneficial, but the risks of hearing loss and impaired vestibular function need to be considered. There appears to be a limited, adjunctive role for some medical therapies aimed at slowing disease progression, which include sodium fluoride and bisphosphonates, although the evidence for this is mixed.(3)
This illustration shows surgically treated otosclerosis, with the ossified stapes removed and a prosthetic replacement implanted in the middle ear. A tympanostomy tube is also shown.
JOHN BAVOSI/SCIENCE PHOTO LIBRARY
Diagnosis and treatment references
1. Foster MF, Backous DD. Clinical Evaluation of the Patient with Otosclerosis. Otolaryngol Clin North Am. 2018;51(2):319-326. doi:10.1016/j.otc.2017.11.004
2. Brown LA, Mocan BO, Redleaf MI. Diagnostic Protocol for Detecting Otosclerosis on High-Resolution Temporal Bone CT. Ann Otol Rhinol Laryngol. 2019;128(11):1054-1060. doi:10.1177/0003489419859036
3. de Oliveira Penido N, de Oliveira Vicente A. Medical Management of Otosclerosis. Otolaryngol Clin North Am. 2018;51(2):441-452. doi:10.1016/j.otc.2017.11.006
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