Pediatric Otosclerosis 

Updated: Mar 23, 2018
Author: Joe Walter Kutz, Jr, MD, FACS; Chief Editor: Ravindhra G Elluru, MD, PhD 

Overview

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.

Usually, symptomatic hearing loss from otosclerosis first develops early in the third decade of life, though onset can occur during childhood. Otosclerosis is well recognized as a cause of conductive hearing loss from fixation of the stapedial footplate in the oval window niche. Less well recognized is 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 necessitates treatment eventually develops in about 1% of the white population. Clinical disease occurs in about 0.5% of people of Asian and South American descent and in about 0.1% of those of African descent. The disease is bilateral in most cases.

For patient education resources, see the Ear, Nose, and Throat Center, as well as Tinnitus.

Pathophysiology

Two separate pathologic phases of the disease process can be identified:

  • Early otospongiotic phase
  • 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.[3]  (See Histologic Findings.)

Epidemiology

Histologically, otosclerosis has a prevalence of about 10%. However, only about 10% of persons with histologic disease are clinically affected, and thus, the prevalence of clinically significant disease is about 1%. The most common 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. Rarely, patients may present with vertigo.[4]

Clinical otosclerosis can manifest as early as age 7-8 years but most commonly appears in persons aged 15-35 years. Women seek medical attention for hearing loss due to otosclerosis more frequently than men do. 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. Otosclerosis is much more common in whites than in persons of other races: Histologic otosclerosis occurs in 10-20% of whites but in only about 1% of people of African descent.

Prognosis

The 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. SNHL can result in total deafness, but such severe progression is uncommon.

 

Presentation

History

Hearing loss and tinnitus are the principal symptoms of otosclerosis. Hearing loss is progressive, but the rate of progression varies, and loss of hearing 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.[4] Dizziness secondary to otosclerosis can be difficult to distinguish from dizziness related to 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 progresses, 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 head of the malleus can occur congenitally, often in association with other stigmata of aural atresia, or it can be acquired, usually from 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, in contrast to the bilateral disease more often seen in otosclerosis.

Paget disease produces a clinical picture indistinguishable from that of 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 or blue sclera), but subtle cases may be indistinguishable from typical otosclerosis. At the time of operation, surgical findings are identical.

Physical Examination

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 stapedectomy procedure.

The Weber test should lateralize to the ear with a greater degree of conductive 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, though they do not rule out the possibility of stapes fixation due to otosclerosis. The exception is the presence of a Schwartze sign, with which increased vascularity is seen over the cochlear promontory. A positive Schwartze sign is a finding characteristic of otosclerosis.

A thorough audiometric evalution is essential before a diagnosis is established or a treatment plan determined.

 

DDx

Diagnostic Considerations

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

In the context of a normal computed tomography (CT) scan, the only way to make a definitive diagnosis of otosclerosis is by means of 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 on the basis of its manifestation in areas other than the otic capsule. Osteogenesis imperfecta, similarly, is diagnosed on the basis of associated symptoms (eg, blue sclerae or multiple fractures).

Another 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 frequently show decreased thresholds in this disease. Electrocochleography usually yields abnormal findings.

Differential Diagnoses

 

Workup

Imaging Studies

In otosclerosis, fine-cut computed tomography (CT) 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.[5] The outlining of the resultant labyrinth is sometimes referred to as a "halo sign."

Audiometric Testing

Diagnosis depends on a combination of audiometric testing and historical features.[6] 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 (sensorineural hearing loss [SNHL] of 20-30 dB at approximately 2000 Hz) is a frequent audiometric finding in otosclerosis but is also seen in other types of conductive hearing loss; it does not represent 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 frequently absent
  • Fine-cut CT often shows 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 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&E) preparations are referred to as blue mantles of Manasse.

 

Treatment

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 and 1970s.[7, 8] Fluoride ions replace the usual hydroxyl group in hydroxyapatite. The result is a fluorapatite complex resistant to osteoclastic degradation.

Although sodium fluoride therapy is now less commonly used, it still has supporters. The recommended dosage is 20-120 mg/day. Effectiveness is monitored by noting the disappearance of the Schwartze sign, repeating audiometric testing, and performing follow-up computed tomography (CT).

Hearing loss can be effectively remediated by using amplification. Hearing aids can often provide almost complete elimination of the conductive hearing loss and aided thresholds can return to near normal.

Their utility notwithstanding, hearing aids can be 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, which produces sound quality that hearing aid users describe as  like "hearing in a barrel." Moreover, the devices are generally not worn at night, are sometimes difficult to adjust, can produce shrill screeching noises (from feedback), and provide unnatural sound quality. Additionally, in 21st-century American society, hearing aids carry the stigma of infirmity or disability.

Surgical Care

Most patients elect surgical repair. If surgery is considered in the pediatric population, the patient should be not be prone to the development of otitis. This could result in a higher incidence of postoperative sensorineural hearing loss (SNHL).[9] 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 in 45-60 minutes with general or local anesthesia.[10, 11, 12]

Procedure

The first step in the surgical procedure is elevation of the tympanic annulus from its sulcus, so 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. Often a small vessel extends 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.

Before 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. Although a hand vein provides an excellent graft, obtaining the graft requires that a second operative site be exposed and prepared. More commonly, tragal perichondrium is used. 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 the 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.

Next, the control hole 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 its 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 that is slightly larger than the piston of a prosthesis. (A laser has also been used to make the hole.[13] ) This procedure is referred to as a stapedotomy[14]  and is to be distinguished from 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.

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

Complications

Various operative and postoperative complications are possible.

In 1-2% of cases, all hearing is lost in the operated ear, resulting in complete SNHL. Such a catastrophic perioperative loss is irremediable. 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 and are relatively easy to repair.

Because the chorda tympani lies directly across the ossicular chain, it must either be mobilized or, in some cases, divided to afford access to the oval window niche. Consequently, 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 treated surgically 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

Medication Summary

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.

Mineral and vitamin supplements

Class Summary

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

Sodium fluoride (Fluoritab, Luride, Pediaflor)

Fluoride is an element essential for the development of healthy teeth and bones.

Vitamin D

Stimulates calcium and phosphate absorption from small intestine and promotes calcium release from bone into blood.

Calcium carbonate (Oystercal)

Used in combination with vitamin D and sodium fluoride.