AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Otosclerosis is a genetically mediated metabolic bone disease that affects only the human otic capsule and ossicles.^{1, 2} Its mode of inheritance is autosomal dominant, but penetrance and expressivity both vary. Women are affected twice as often as are men.

Usually, symptomatic hearing loss from otosclerosis first develops early in the third decade of life, although onset in the teenage years does occur. Otosclerosis is well recognized as a cause for conductive hearing loss due to fixation of the stapedial footplate in the oval window niche. Less well recognized is the fact that otosclerosis can involve other portions of the cochlea and produce sensorineural hearing loss (SNHL). The incidence of cochlear otosclerosis and that of cochlear otosclerosis resulting in clinically significant SNHL are unclear. The disease occurs in 8-10% of the white population; however, of those individuals affected, only 10-15% have clinical symptoms. Consequently, conductive hearing loss that requires treatment eventually develops in about 1% of the white population. Clinical disease occurs in about 0.5% of Asians and South Americans and in about 0.1% of Africans. The disease is bilateral in most cases.

Pathophysiology

Two separate pathologic phases of the disease process can be identified: an early otospongiotic phase and a later otosclerotic phase.

The otosclerotic phase begins when osteoclasts are slowly replaced by osteoblasts and dense sclerotic bone is deposited in the areas of previous bone resorption. When this process involves the oval window in the area of the footplate, the footplate becomes fixed, resulting in conductive hearing loss.

See Histologic Findings below.

Frequency

United States

Histologically, otosclerosis has a prevalence of about 10%. However, only about 1 in 10 persons with histologic disease are clinically affected, thus placing the prevalence of clinically significant disease at about 1%.

Mortality/Morbidity

The only known morbidity from otosclerosis is hearing loss. Although conductive hearing loss is considered the hallmark of the disease, involvement of portions of the otic capsule other than the stapedial footplate can result in SNHL.

Race

Otosclerosis is much more common in whites than in persons of other races. Histologic otosclerosis occurs in 10-20% of whites but only about 1% of blacks.

Sex

More women seek medical attention for hearing loss due to otosclerosis than do men. However, the disease is not sex-linked, and a histologic study of a large series of temporal bones shows no difference in prevalence between men and women.

Age

Clinical otosclerosis can manifest as early as age 7-8 years but most commonly appears in persons aged 15-35 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Hearing loss and tinnitus are the principal symptoms of otosclerosis. Hearing loss is progressive but the rate of progression varies and may proceed by fits and starts, even within the same individual. Tinnitus widely varies but generally tends to become more severe as the degree of hearing loss worsens. Occasionally, dizziness can result. The patient may describe only vague disequilibrium or may experience paroxysms of severe rotatory vertigo. Dizziness due to otosclerosis alone is sometimes termed otosclerotic inner ear syndrome. Dizziness secondary to otosclerosis can be difficult to distinguish from other causes, especially secondary endolymphatic hydrops (ie, Ménière syndrome).

• In individuals with a significant history of otitis media, ossicular pathology, especially partial or complete necrosis of the long process of the incus, should be seriously considered. In such circumstances, tympanography may reveal very high compliance (ie, the opposite of otosclerosis). A type AD tympanogram suggests ossicular discontinuity. Often, as incus necrosis proceeds, the union between the incus and the stapes is replaced by a dense fibrous band. Such a fibrous union may result in an air-bone gap that is wider in high frequencies than in low frequencies.
• Congenital stapes fixation is nonprogressive and is detected in the first decade of life. Fixation of the malleal head can occur congenitally, often in association with other stigmata of aural atresia, or it can be acquired, usually due to an infectious process that resulted in tympanosclerosis. Tympanosclerosis can also result in stapes immobility by filling the oval window niche with tympanosclerotic plaques. Such a process usually occurs in individuals with a long history of otitis media and is more commonly unilateral than is otosclerosis.
• Paget disease produces a clinical picture indistinguishable from otosclerosis. Histopathologically, Paget disease begins in the periosteal layer and not within the otic capsule.
• Osteogenesis imperfecta also results in stapes fixation. Osteogenesis imperfecta is readily identified in most individuals who have other stigmata of the disease (eg, multiple flexures, blue sclera) but subtle cases may be indistinguishable from typical otosclerosis. At the time of operation, surgical findings are identical.

Physical

• Tuning fork tests reveal a conductive hearing loss in individuals with footplate fixation. Results of tuning fork tests may be difficult to interpret in patients with mixed losses.
• The Rinne test should demonstrate bone conduction to be better than air conduction (negative Rinne) in patients contemplating a stapes procedure.
• The Weber test should lateralize to the ear with a greater degree of conducting hearing loss.
• The remainder of the physical examination findings should be normal.
• Abnormalities of the tympanic membrane, external ear canal, or middle ear suggest other causes for conductive hearing loss, although they do not rule out the possibility of stapes fixation due to otosclerosis. The exception is the presence of a Schwartze sign. Upon physical examination, this is the finding characteristic of otosclerosis.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Differential diagnosis of otosclerosis should include other causes of conductive hearing loss.

• In the context of a normal CT scan result, the only way to make a definitive diagnosis of otosclerosis is by exploratory tympanotomy and palpation of the stapes.
• A history of recurrent otitis media suggests an ossicular discontinuity due to incus necrosis or ossicular chain fixation due to tympanosclerosis.
• Congenital stapedial footplate fixation is present at an earlier age than juvenile otosclerosis. Congenital footplate fixation is generally detectable at age 3 years, whereas juvenile otosclerosis is rarely if ever detected before age 10 years.
• Paget disease can be diagnosed based on its manifestation in areas other than the otic capsule. Osteogenesis imperfecta, similarly, is diagnosed on the basis of associated symptoms (eg, blue sclerae, multiple fractures).
• A newly diagnosed cause of conductive hearing loss is dehiscent semicircular canal syndrome. This disorder is classically associated with Tullio phenomenon (vertigo and/or nystagmus associated with loud noises). Diagnosis depends on CT scans that reveal a dehiscent superior semicircular canal when the appropriate symptomatology is present. Tullio phenomenon should be objectively documented. Vestibular evoked myogenic responses are frequently altered in this disease.
• Other problems to be considered include the following:
• • Ossicular discontinuity
  • Fixation of the head of the malleus or incus
  • Congenital stapes fixation
  • Paget disease
  • Superior semicircular canal dehiscence syndrome

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Imaging Studies

• In otosclerosis, fine-cut CT scanning can often reveal deposition of new bone in the area of the round or oval window and/or otosclerotic foci within other portions of the labyrinthine capsule and cochlea. The outlining of the resultant labyrinth is sometimes referred to as a "halo sign."

Other Tests

• Diagnosis depends on a combination of audiometric testing and historical features. An audiometric evaluation reveals conductive hearing loss with absent stapedius reflex. Historically, patients report a relatively slowly progressive hearing loss in the absence of significant infectious ear disease or otologic trauma. Several other indications that can support the diagnosis include the following:
• • The Carhart notch is a frequent audiometric to otosclerosis but is also seen in other types of conductive hearing loss. It consists of the appearance of a sensorineural hearing loss (SNHL) of 20-30 decibels (dB) at approximately 2000 cycles per second. The Carhart notch does not represent a genuine SNHL because it disappears after successful stapedectomy.
  • Speech discrimination is usually excellent.
  • A type A tympanogram with very low compliance may be noted. Sometimes termed a stiffness curve, this is often referred to as an A_s pattern. This configuration is occasionally present but is frequently absent.
  • Fine-cut CT scanning can often show deposition of new bone in the area of the round or oval window and/or otosclerotic foci within other portions of the labyrinthine capsule and cochlea.
  • Vestibular testing should be included when dizziness is present. Although no findings are characteristic for otosclerotic inner ear syndrome, findings suggestive of either superior semicircular canal dehiscence or of Ménière disease alter treatment plans.
• Audiometric testing is the principal study required for the management of otosclerosis. Both air and bone conduction must be evaluated. If the clinical manifestations are all due to footplate fixation, audiography reveals a purely conductive loss. If involvement of the otic capsule in other areas causes hair cell injury, SNHL is also detected. No explicit criteria have been developed that allow the clinician to definitively distinguish SNHL caused by otosclerosis from hearing loss due to other causes.
• Diagnosis of cochlear otosclerosis (ie, SNHL due to otosclerosis) generally requires a halo sign on fine-cut CT scanning or SNHL that is more advanced than expected from presbycusis, in the presence of some sign of stapedial involvement (eg, conductive hearing loss from footplate fixation, abnormalities of stapedius reflex testing).

Histologic Findings

• The otospongiotic phase of the disorder is characterized by bone resorption. Several cell types, such as histiocytes, osteocytes, and osteoblasts, participate in this process.
• Bone resorption begins around existing vessels with consequent enlargement of vascular channels. Resultant hypervascularization, or a red blush, seen on the medial wall of the inner ear through the tympanic membrane is the Schwartze sign. This hypervascularization can sometimes be visualized during clinical otoscopy.
• As the otospongiotic phase continues, a ground substance is deposited as a replacement for resorbed bone. The result is new spongy bone that has a blue appearance on histologic staining. These blue areas seen on hematoxylin and eosin (H and E) preparations are referred to as blue mantles of Manasse.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

For the vast majority of patients with otosclerosis, the principal goal is remediation of hearing loss. Only a small minority of patients have vestibular symptoms that are pronounced and warrant treatment solely on that basis.

• Use of sodium fluoride to arrest development of otosclerosis was championed by Shambaugh and was fairly widespread in the 1960s-70s.^{3, 4} Fluoride ions replace the usual hydroxyl group in hydroxy apatite. The result is a fluorapatite complex resistant to osteoclastic degradation. Sodium fluoride therapy is used less commonly now, but it still has supporters. The recommended dosage is 20-120 mg/d. Effectiveness is monitored by noting the disappearance of Schwartze sign, repeated audiometric testing, and follow-up CT scanning.
• Hearing loss can be effectively remediated using amplification. Hearing aids can often provide almost complete elimination of the conductive hearing loss and aided thresholds can return to near normal. Although useful, hearing aids are poorly accepted for various reasons. The presence of the occlusive mold within the external auditory canal produces an unpleasant effect, termed the canal occlusion effect. Individuals who use hearing aids report that the effect produces sound quality similar to that of "hearing in a barrel." Moreover, the devices are generally not worn at night, are sometimes difficult to adjust, can produce shrill screeching noises (as a result of feedback), and do not provide natural sound quality. Additionally, in 20th century American society, hearing aids carry the stigma of infirmity or disability.

Surgical Care

Most patients elect surgical repair. Surgery for otosclerosis is very successful, and more than 90% of patients experience complete elimination of conductive hearing loss (ie, <10 dB of residual air bone gap). The operation is a day surgical procedure that can be performed under general or local anesthesia. The operation is completed in 45-60 minutes.

• The first step in the surgical procedure is elevation of the tympanic annulus from its sulcus, such that the tympanic membrane can be reflected anteriorly. Elevation provides access to the entire posterior middle ear, including the ossicular chain. Once the drum has been elevated, small instruments are used to palpate the ossicular chain and to confirm that the stapes is fixed and immobile within the oval window niche. Once the diagnosis is confirmed, incisions are made in the mucosa around the footplate to free it from the remainder of the middle ear mucosa. Generally, a small vessel extends anteriorly just over the anterior lip of the oval window niche. This vessel can produce significant bleeding and should be controlled prior to attempted footplate removal so that the bleeding can be controlled before the oval window is opened.
• Prior to removal of the stapes, a graft must be obtained that can be used to seal the open oval window after footplate removal.
• • A small piece of vein can be taken from the hand. The hand provides an excellent graft; however, a second operative site must be exposed and prepared. Tragal perichondrium is used more commonly. Perichondrium can be obtained from the tragus of the ear within the same surgical field.
  • A measurement is made to determine how long the prosthesis needs to be.
  • Once the graft material has been obtained and cut to the appropriate size, a control hole is made in the center of the fixed footplate. After a control hole has been made, the incudostapedial joint is separated, and the stapedius tendon is cut. The suprastructure of the stapes then is fractured away. Because the stapes footplate is fixed in the oval window, pressure on the crura causes them to fracture at their base. The control hole now is slightly enlarged (0.1 mm) with a right angle hook. Larger instruments are used to extract the remainder of the footplate. The graft then is placed over the open oval window, and the prosthesis is positioned to span the gap between the distal portion of the incus and the grafted oval window. The eardrum is returned to anatomic position, and the procedure is terminated after the canal has been filled with nonototoxic antibacterial ointment.
• As an alternative to removal of the entire footplate, a small hole can be drilled into the footplate itself just sufficient to accommodate the end of the prosthesis. Such a procedure is referred to as a stapedectomy as opposed to the classic stapedectomy, in which the complete footplate is removed. Both procedures have high success rates, and little long-term difference between them has been demonstrated.
• Various operative and postoperative complications are possible.
• • In 1-2% of cases, all hearing is lost in the operated ear, resulting in complete sensorineural hearing loss (SNHL). Such a catastrophic perioperative loss is unremediable. Neither revision surgery nor amplification provides any meaningful hearing improvement. The exact circumstances that create such catastrophic injuries are unclear. However, cases of complete SNHL that follow an entirely uneventful surgical procedure are well documented.
  • Permanent facial nerve injury occurs in fewer than 1 per 100 (probably <1 per 1000) cases.
  • In 1-2% of cases, a tympanic membrane perforation results from elevation of the eardrum. Such tympanic membrane perforations are generally in the posterior quadrant and are relatively easy to repair.
  • Because the chorda tympani lies directly across the ossicular chain, it must either be mobilized or, in many cases, divided to access the oval window niche. Consequently, some alteration of taste may follow the operation. This condition generally resolves in a few weeks to a couple of months.
  • Dysequilibrium and vertigo with nausea and vomiting are frequent in the immediate postoperative period and often last for several days. Long-term balance disturbance occurs but is very uncommon.
  • Individuals may develop tinnitus after the operation. Some patients who had tinnitus preoperatively have worse tinnitus postoperatively. However, most patients who experience hearing improvement report either significant improvement in their tinnitus or no meaningful change.
• The operation is performed in only one ear at a time; the worst-hearing ear should be approached first. Many patients desire correction of the second ear if the operation on the first ear was successful. The second ear should be subjected to surgery only if the surgeon is convinced that the operation has been successful in the first ear and that the result is permanent. As a general rule, 3-12 months should elapse between the first and second operations.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Sodium fluoride and calcium are the only drugs used in the treatment of otosclerosis; however, because it is typically not apparent until late adolescence, studies in pediatrics have not been pursued.

Drug Category: Mineral and vitamin supplements

Sodium fluoride is thought to mature the active focus of otospongiosis and to limit progression of the disease, especially sensorineural hearing loss (SNHL).

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• In patients with otosclerosis, audiography should be performed on an annual basis indefinitely.

Prognosis

• Clinical progression of the disease is unpredictable. Bilateral involvement is typical, and, in most cases, conductive hearing loss progresses until the maximal 50-60 dB loss develops.
• Sensorineural hearing loss (SNHL) can result in total deafness, but such severe progression is uncommon.

Patient Education

• For excellent patient education resources, visit eMedicine's Ear, Nose, and Throat Center. Also, see eMedicine's patient education article Tinnitus.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• No unusual or unexpected areas of medicolegal exposure in otosclerosis are recognized.
• The most likely causes of action would be failure to diagnose or failure to inform parents of treatment alternatives. In the latter context, all patients with otosclerosis and their families must recognize that hearing aids work fairly well to remediate hearing loss and that surgery, although the preferred treatment, is not the only treatment

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Gordon MA. The genetics of otosclerosis: a review. Am J Otol. Nov 1989;10(6):426-38. [Medline].
2. Ealy M, Chen W, Ryu GY, et al. Gene expression analysis of human otosclerotic stapedial footplates. Hear Res. Jun 2008;240(1-2):80-6. [Medline].
3. Shambaugh GE Jr, Causse J. Ten years experience with fluoride in otosclerotic (otospongiotic) patients. Ann Otol Rhinol Laryngol. Sep-Oct 1974;83(5):635-42. [Medline].
4. Shambaugh GE Jr, Petrovic A. Effects of sodium fluoride on bone. Application to otosclerosis and other decalcifying bone diseases. JAMA. Jun 10 1968;204(11):969-73. [Medline].
5. Causse JR, Causse JB, Bretlau P, et al. Etiology of otospongiotic sensorineural losses. Am J Otol. Mar 1989;10(2):99-107. [Medline].
6. Dornhoffer JL, Bailey HA Jr, Graham SS. Long-term hearing results following stapedotomy. Am J Otol. Sep 1994;15(5):674-8. [Medline].
7. Hannley MT. Audiologic characteristics of the patient with otosclerosis. Otolaryngol Clin North Am. Jun 1993;26(3):373-87. [Medline].
8. Hinojosa R, Marion M. Otosclerosis and sensorineural hearing loss: a histopathologic study. Am J Otolaryngol. Sep-Oct 1987;8(5):296-307. [Medline].
9. Hough JV, Dyer RK Jr. Stapedectomy. Causes of failure and revision surgery in otosclerosis. Otolaryngol Clin North Am. Jun 1993;26(3):453-70. [Medline].
10. Iurato S, Ettorre GC, Onofri M, Davidson C. Very far-advanced otosclerosis. Am J Otol. Sep 1992;13(5):482-7. [Medline].
11. Linthicum FH Jr. Histopathology of otosclerosis. Otolaryngol Clin North Am. Jun 1993;26(3):335-52. [Medline].
12. Rama-Lopez J, Cervera-Paz FJ, Manrique M. Cochlear implantation of patients with far-advanced otosclerosis. Otol Neurotol. Feb 2006;27(2):153-8. [Medline].
13. Rizer FM, Lippy WH. Evolution of techniques of stapedectomy from the total stapedectomy to the small fenestra stapedectomy. Otolaryngol Clin North Am. Jun 1993;26(3):443-51. [Medline].
14. Roland PS, Meyerhof WL. Otosclerosis. In: Head and neck Surgery-Otolaryngology. Vol 2. 1998:2083-97.
15. Willis R. Stapedectomy--past and present. Ann Acad Med Singapore. Sep 1991;20(5):680-5. [Medline].
16. Zehnder AF, Kristiansen AG, Adams JC, et al. Osteoprotegrin knockout mice demonstrate abnormal remodeling of the otic capsule and progressive hearing loss. Laryngoscope. Feb 2006;116(2):201-6. [Medline].

Article Last Updated: Oct 16, 2008