Chapter 51. Otosclerosis

• Slowly progressive unilateral or bilateral conductive hearing loss
• Most commonly presents by the third and fourth decades
• Family history of otosclerosis
• Normal otoscopic examination or positive Schwartze sign
• Audiogram with Carhart notch and abnormal or absent stapedial reflexes.

Otosclerosis is a disease process unique to the temporal bone and unlike other generalized bone dyscrasias such as Paget disease and osteogenesis imperfecta; it nearly exclusively involves the otic capsule. Disease progression is characterized by abnormal removal of mature dense otic capsule bone by osteoclasts, and replacement with the woven bone of greater thickness, cellularity, and vascularity. While otosclerosis may potentially involve any part of the bony labyrinth, it carries a distinct predilection for the region near the anterior border of the oval window (fissula ante fenestram). When disease involves the annular ligament of the oval window and stapes footplate, a conductive hearing loss (CHL) invariably occurs. Involvement of other parts of the otic capsule may result in sensorineural hearing loss (SNHL) and vestibular symptoms.

The true prevalence of histological otosclerosis is unknown. Estimates reported for clinical disease (ie, clinical otosclerosis) range from 0.5% to 1.0%. However, the incidence of subclinical disease (ie, histologic otosclerosis) in unselected autopsy series has been reported as high as 13%. About 15 million people in the United States have been diagnosed with otosclerosis, and it is considered among the most common causes of acquired hearing loss. Compared to caucasians, otosclerosis is half as prevalent among Asians (0.5%) and one-tenth as common in African-American patients (0.1%). In practice, otosclerosis is seen more often in women than in men by the ratio of approximately 2:1. However, it has been proposed that the incidence may be the same in both sexes and that hormonal influences during pregnancy might cause a more rapid progression in women, bringing them to clinical attention. Symptoms rarely become apparent before late teens, with most patients presenting between the age of 20 and 45.

The otic capsule and stapes form from a cartilaginous anlage, which begins endochondral ossification by the 19th week of embryogenesis and is complete by the end of the first year of life. The vestibular surface of the footplate remains cartilaginous throughout life. Bone turnover, which is normally seen in other parts of the body, does not occur in the “healthy” otic capsule after initial development. However, with otosclerosis there is increased osteoblastic and osteoclastic activity and vascular proliferation. The otosclerotic focus is defined by an area of increased bony turnover and metabolic activity and the term “otospongiosis” is most descriptive of the histologic appearance at this stage of the disease. As the disease stabilizes or “burns out,” the normal bone of the otic capsule is replaced with a focus of metabolically quiescent, dense mineralized bone. The most common location of the otosclerotic focus is the region of the otic capsule anterior to the stapes footplate (the region of the fissula ante fenestram). Fixation of the stapes begins as the lesion spreads to involve the annular ligament. Extension over the footplate is uncommon but may lead to total obliteration of the footplate. Less frequently, lesions may extend into the inner ear resulting in hyalinization of the spiral ligament and SNHL. Rare cases of pure SNHL from isolated cochlear otosclerosis without ossicular involvement have been reported.

The inciting stimulus for the abnormal bone remodeling in otosclerosis is unknown and has been attributed to both genetic and environmental factors. In most cases, the disease is inherited as a simple autosomal dominant trait with incomplete penetrance and variable expressivity. Recent findings suggest an association between the measles virus and otosclerosis; whether the measles virus is a factor that can initiate the otospongiotic process remains to be determined.

Symptoms and Signs

The typical patient with otosclerosis presents with a history of slowly progressive hearing loss that is usually bilateral and asymmetric, although unilateral disease may occur in up to 30% of patients. Patients with CHL including those with otosclerosis may also report improved hearing with background noise, a paradoxical phenomenon known as paracusis of Willis. Hearing deficits typically become apparent when they reach a 25–30 dB loss whereat the patient has difficulty understanding speech. Tinnitus is a common complaint and may be an indication of sensorineural degeneration. Fluctuations in hearing are uncharacteristic but may occur during times of hormonal instability (eg, during pregnancy) and patients rarely have complaints of vertigo.

Physical Exam

Otoscopic examination is essential and best performed with an operating microscope. The goal of the exam is to exclude other causes of a CHL, such as cholesteatoma, tympanosclerosis, and middle ear effusion or masses. Even with advanced otosclerosis, the tympanic membrane is normal, the middle ear space is pneumatized, and the malleus should move with pneumatic otoscopy. In active disease, the astute clinician may appreciate a reddish blush (Schwartze sign) over both the promontory and the oval window niche owing to the prominent vascularity associated with an otospongiotic focus.

Tuning fork tests (Rinne and Weber) should be carefully performed at 256, 512, and 1024 Hz to confirm the findings of the audiogram. Weber testing should lateralize to the ear with the greatest conductive deficit and a negative Rinne test (bone conduction greater than air conduction) at 512 Hz usually indicates an air-bone gap of at least 25 dB (Table 51–1).

Imaging Studies

Computerized Tomography (CT) Scanning

High-resolution CT scanning (less than 1 mm slices) provides excellent visualization of the anatomy of the middle ear and otic capsule and for this reason is the initial imaging modality of choice when the diagnosis is in question. It is valuable in assessing the pathology of the oval window and footplate, and the extent of otic capsule involvement and may also be helpful in identifying contralateral subclinical disease. CT scanning may show subtle areas of demineralization, which are typically located just anterior to the oval window (Figure 51–1), as well as thickening of the footplate. In a recent study examining 209 cases of otosclerosis, 95.8% of patients having confirmed otosclerosis had identifiable preoperative findings on CT. With cochlear involvement, there is a demineralization of the otic capsule (Figure 51–2), which yields the so-called halo sign or double ring sign seen on CT as a low-density zone outlining the basal turn of the cochlea.

In the sclerotic phase of disease or after fluoride therapy, remineralization may occur and CT findings may be indistinguishable from the normal otic capsule. A CT scan is not necessary in most cases but should be considered when the patient has vertigo, SNHL, poor word recognition or if there is a concern for superior semicircular canal dehiscence syndrome. A CT scan is routinely obtained in pediatric patients given the extremely low prevalence in this age group and because of the higher risk of otic capsule and temporal bone malformations.

Magnetic Resonance Imaging (MRI)

MRI provides very limited information regarding otic capsule pathology and is not obtained for routine cases of otosclerosis. In patients with an atypical presentation (pediatric onset, vertigo, SNHL) MRI may detect congenital anomalies of the labyrinth, fibrosis within the cochlea and can exclude retrocochlear pathology, such as an acoustic neuroma. During active disease, T1-weighted images show a loss of normal signal void from the otic capsule. Soft tissue or intermediate signal density may be noted in or around the otic capsule, and contrast-enhanced T1-weighted images can show enhancement of the pericochlear otic capsule. T2-weighted images may be beneficial for preoperative cochlear implant evaluation; a reduction or loss of the normal fluid signal from the membranous labyrinth depicts intracochlear fibrosis or bone deposition, which may hinder full electrode insertion (Figure 51–3).

Special Tests

Given the relatively normal exam findings, audiometric testing is one of the most important tools in evaluating a patient suspected of having otosclerosis. Testing patients who have a mixed hearing loss or far-advanced otosclerosis can be problematic because of masking dilemmas and audiometer limits. An experienced audiologist is invaluable in providing accurate and complete information on this type of testing.

Pure-Tone Audiometry

On pure-tone audiometry, patients with early otosclerosis present with progressive low-frequency CHL. As otosclerosis spreads to involve the entire stapes, an increase in mass compounds the progressive increase in stiffness, resulting in (1) progression of loss in the high frequencies, (2) a gradual widening of the air-bone gap, and (3) a flat audiogram configuration. In the absence of SNHL, pure conductive loss seen with a completely fixed stapes are limited to a 60 to 65 dB hearing level with a maximum air-bone gap across the frequency range. As the disease spreads to involve the cochlea, bone conduction thresholds increase, resulting in a mixed hearing loss in which most of the conductive components are confined to the low frequencies. Decreased bone conduction levels in high frequencies usually represent a true SNHL.

The hallmark of bone conduction thresholds in otosclerosis is the Carhart notch (Figure 51–4). This is characterized by the elevation of bone conduction thresholds of approximately 5, 10, and 15 dB at 500, 1000, and 2000 Hz, respectively. The Carhart notch is thought to result from the disruption of normal ossicular resonance, which is approximately 2000 Hz. It is therefore a mechanical phenomenon and not a true reflection of cochlear reserve since it reverses after successful surgery (see Table 51–1).

Tympanometry

The gradual stiffening of the ossicular chain produced by progressive stapes fixation leads to specific patterns of change on tympanometry. Because middle ear aeration is not affected by otosclerosis, patients with early- and mid-stage disease characteristically have a normal Type A tympanogram. Progressive stapes fixation results in a Type AS (A-shallow) tympanogram (Figure 51–4).

Acoustic Reflex (Stapedial Reflex)

One of the earliest signs of otosclerosis is an abnormal acoustic reflex pattern often preceding the development of an air-bone gap. In the normal hearing ear, the configuration of the acoustic reflex pattern is one of a sustained decrease in compliance owing to the contraction of the stapedial muscle that lasts the duration of the stimulus. In contrast, with early otosclerosis a pathognomonic biphasic “on-off” pattern characterized by a brief increase in compliance at the onset and at the termination of the stimulus occurs. With disease progression, a reduction in the reflex amplitude is seen, followed by elevation of ipsilateral, then contralateral thresholds, and finally, the disappearance of the response. The most common finding at presentation is absent reflexes.

The diagnosis of otosclerosis may be strongly suspected based on the history, physical exam, audiometric findings, and CT scan. However, the diagnosis is confirmed at the time of surgery or upon histologic study of the temporal bone. Other lesions that may cause a CHL are numerous (Table 51–2).

Patients with otosclerosis may be managed by (1) observation, (2) pharmacologic therapy, (3) amplification, and (4) surgery or a combination thereof. The advantages and disadvantages of each should be discussed with the patient to guide informed consent.

Observation

Observation is the most inexpensive and least risky option. It is often the strategy preferred for patients with unilateral disease and those with a mild CHL. If the patient is not troubled by the degree of hearing loss, then no intervention is indicated and audiograms are usually obtained on yearly basis. The natural history of disease progression would predict further hearing loss over time and ultimately this might prompt intervention.

Nonsurgical Measures

Therapeutic strategies to prevent the progression of otosclerosis have been directed toward the suppression of bone remodeling with fluorides and bisphosphonates. However, the efficacy of these agents has not been definitively proven and otologists vary widely in their recommendations regarding their use.

Sodium Fluoride Therapy

Fluoride reduces osteoclastic bone resorption and increases osteoblastic bone formation. Together, these actions may promote recalcification and reduce bone remodeling in actively expanding osteolytic lesions. Sodium fluoride is also thought to inhibit proteolytic enzymes that are cytotoxic to the cochlea and that may lead to SNHL.

Many otologists recommend the use of sodium fluoride in patients with new-onset otosclerosis, rapidly progressive disease, or inner ear symptoms such as SNHL and dizziness. The treatment is usually continued for 1–2 years. Patients with cochlear otosclerosis may be treated for longer periods of time or even indefinitely.

Bisphosphonates

Bisphosphonates are potent antiresorptive agents that are useful for the prevention and treatment of osteoporosis and other conditions characterized by increased bone remodeling. They have been widely used in the treatment of osteoporosis and hold some promise in controlling otosclerosis. Following oral intake, bisphosphonates are incorporated into the bone, where they inhibit the osteoclastic activity. The most promising bisphosphonates in clinical use include alendronate, etidronate, risedronate, and zoledronate. These bisphosphonates potently inhibit bone resorption without significantly affecting bone deposition.

Amplification

Most patients with otosclerosis have normal cochlear function with excellent speech discrimination and are therefore good hearing aid candidates. Before proceeding with surgery, patients should be encouraged to try a hearing aid (or aids). Some patients become successful hearing aid users and can therefore avoid surgery and its risks. However, although there is little risk to the patient with hearing aid use, there are some significant disadvantages when compared with the result of a successful surgery. The disadvantages include a poorer sound quality, cosmesis, cost, maintenance requirements, being able to hear only when the aid is in use, occlusion effect, and potential discomfort. In practice, most patients with good sensorineural reserve prefer to have surgery.

Patients with a severe to profound mixed hearing loss may require surgical correction of the conductive loss in order to gain benefit from a hearing aid. For patients who gain limited benefit from conventional hearing aids cochlear implantation is an effective alternative.

Surgical Measures

Indications for Surgery

Most patients with CHL due to otosclerosis can be treated surgically (Table 51–3). The average patient with otosclerosis and a bone conduction level of 0–25 dB in the speech range (250–4000 Hz) and an air conduction level of 45–65 dB is a suitable candidate for surgery; an air-bone gap of at least 15 dB and speech discrimination scores of 60% or better are preferred. Clearly, those with a larger preoperative air-bone gap have more to gain from surgical intervention. If bilateral disease is present, generally the poorer hearing ear should be chosen. If the patient is a candidate for bilateral surgery, the poorer ear should undergo surgical correction first. It is recommended that the surgery on the contralateral ear be delayed at least 6 months to allow the patient to adjust to the first ear and assure stability of the hearing result.

A subset of patients with a severe-to-profound mixed hearing loss have been referred to as having far-advanced otosclerosis. In such cases, the otosclerotic process has progressed to the point where there is minimal to no detectable air conduction threshold and bone conduction is difficult to interpret at high levels because of vibrotactile sensations. Many such patients have been successfully treated with stapedotomy with postoperative amplification. Patients who do not gain sufficient benefit with amplification should be considered for cochlear implantation.

Preoperative Counseling

Surgery for otosclerosis is an elective procedure and should be preceded by a thorough explanation of all treatment alternatives. With refined techniques and new technologies, excellent outcomes (air-bone gap closure of less 10 dB) should be expected in over 90% of cases; however, the patient must be informed about the potential for short-term and long-term failure, the possible need for revision surgery and potential complications. In the long term, patients with otosclerosis lose inner ear function at a more rapid rate than the general population, and they are therefore more likely to eventually need a hearing aid even despite a successful surgery.

Preoperative Considerations

Surgery may be performed under local or general anesthesia depending on the preference of both the patient and the surgeon. There are several advantages to local anesthesia. (1) The patient's hearing can be tested after prosthesis placement by repositioning the tympanic membrane and either talking with the patient, performing tuning fork tests or even abbreviated intraoperative audiometry. (2) If the patient complains of vertigo during the procedure, the surgeon can alter his or her technique to reduce vestibular irritation. (3) The patient can avoid the postoperative nausea that often accompanies general anesthesia; the newly reconstructed ear is therefore not subjected to the potential extreme pressures associated with arousal from anesthesia. Despite these potential advantages the use of a general anesthetic is preferred by many surgeons. Patients operated under local anesthesia may experience pain, become anxious, and move unpredictably resulting in a more difficult and risky surgery.

Surgical Technique

Over the years there have been numerous advancements that have led to the currently employed surgical strategy. Many subtle variations of technique are used by surgeons but the basic concept and steps of the procedure are similar.

After adequate cleaning of the ear and administration of both a local anesthetic and a vasoconstrictive agent, a tympanomeatal flap is elevated to expose the middle ear space. If the stapes cannot be well visualized, the scutum is removed with a curet or drill. The ossicular chain is inspected and palpated to confirm the diagnosis of otosclerosis. Once the diagnosis is made, there is considerable variation in how a surgeon can handle the stapes superstructure and footplate. Typically, the incudostapedial joint is separated, the stapes superstructure removed and either a small fenestra stapedotomy or a total stapedectomy is performed, and the prosthesis is placed from the incus through the opening into the vestibule (Figure 51–5). The mobility of the prosthesis is assessed by gentle palpation of the malleus. Tissue or blood is used to seal the area around the prosthesis, and the tympanic membrane is repositioned. If surgery is performed under local anesthesia, intraoperative hearing improvement can be confirmed at this point by whispering in the patient's ear, the use of tuning forks or even abbreviated intraoperative audiometric testing. Most surgeons allow the patient to return home the day of the surgery.

Laser Use

Lasers are commonly used in otosclerosis surgery. The cited advantages of laser use are an improved ability to prepare a bloodless fenestra, precise ablation of the footplate, and a reduced risk of footplate subluxation. Lasers are also used to generate heat to activate shape memory or self-crimping Nitinol prostheses. Various types of lasers have been safely used, including the CO2, KTP, and argon.

Cochlear Implantation

Patients with severe to profound hearing loss secondary to otosclerosis usually derive excellent benefit from cochlear implantation. However, implantation can be complicated by ossification or soft tissue fibrosis within the cochlea that may preclude a routine full electrode insertion. Preoperative imaging should alert to the surgeon to this possibility and the need for more advanced surgical maneuvers such as drilling the basal turn, placement in the scala vestibuli or other modification of the standard insertion technique.

After device activation there is a reported higher incidence of facial nerve stimulation from current spread through the otosclerotic bone. Reprogramming the device and eliminating the offending channels can usually eliminate this undesirable side effect. In a more recent study, increased speech perception outcomes were associated with less severe signs of otosclerosis on CT scan, full insertion of the electrode, little or no facial nerve stimulation, and a limited need for channel inactivation.

Revision Surgery

Most patients should be encouraged to try a hearing aid before a revision because of the increased risk of SNHL with the second procedure. Only experienced stapes surgeons should perform revision surgery. The reasons for failure of the initial surgery can include incus necrosis, displacement of the prosthesis from the incus or oval window, insufficient stapedotomy size, and reobliteration of the oval window. It is also important to consider the possibility of previously unrecognized diagnosis such as malleus or incus fixation or superior semicircular canal dehiscence syndrome. Because the risk of hearing loss is higher in revision surgery, it is advisable to approach the surgery with an idea of exploring the ear and proceeding with the revision surgery only if it appears favorable.

Patients with SNHL are less likely to benefit from revision surgery. In a large series, up to 80% of patients with postoperative SNHL had no identifiable cause on revision exploration. It is now recommended that for those with postoperative SNHL, only patients with a history of trauma or dizziness be considered for revision. Such circumstances might be caused by a persistent perilymphatic fistula and be amenable to surgical correction.

Stapes Surgery in Children

With the increased risk of congenital malformations and the low overall incidence of pediatric disease, CT is always recommended on younger patients suspected of having otosclerosis. Owing to the rarity of juvenile otosclerosis, the effectiveness of stapedectomy surgery in children has been less critically reviewed. Pediatric patients are more likely to require the use of a drill (“drill-out stapedotomy”) for obliterative otosclerosis as compared to their adult counterparts. Despite this finding, reports have disclosed up to a 91.7% success rate in achieving a 10 dB air-bone gap after five or more years of follow-up. Other studies reported an 82% success rate in primary otosclerosis cases but only a 44% success rate in cases of congenital footplate fixation.

The optimal time for surgery in children remains a point of controversy. With the higher incidence of otitis media during childhood, there is concern for the potential spread of infection through the oval window resulting in meningitis. Moreover, most children benefit from amplification, and delaying surgery until they are older is an acceptable option.

Table 51–4 details some of the potential complications that may result from stapes surgery.

Tympanic Membrane Perforation

If a tympanic membrane perforation is created during flap elevation this is repaired with a soft tissue underlay technique using temporalis fascia. Occasionally, the surgeon will find that the elevated flap is too short after bone has been removed from the scutum; such defects maybe repaired with temporalis fascia, or tragal perichondrium.

Dysgeusia

All efforts should be made to preserve the chorda tympani nerve and minimize manipulation. The nerve is particularly vulnerable during the removal of scutum. Injuring the nerve may result in dysgeusia causing a salty or metallic taste. Although controversial, many authors suggest sharply dividing a stretched or torn chordae tympani nerve to reduce the risk of taste disturbance postoperatively. Typically, taste changes gradually resolve over a few weeks or months; but occasionally they do persist indefinitely.

Abnormalities of the Facial Nerve

Histological dehiscence of the facial nerve occurs in as many as 40% of temporal bone specimens and clinically may be seen in the vicinity of the oval window in about 0.5% of cases. A dehiscent or aberrant facial nerve course may restrict safe access to the footplate and early recognition is critical to preventing injury, particularly if a laser is used. A facial nerve monitor may also be of benefit in preventing nerve injury. If one's view is only mildly hindered the experienced surgeon may cautiously proceed; however, in the rare case of extreme overhang, the case may be terminated given the unfavorably high risk of facial nerve injury.

After surgery, a patient may experience an acute facial nerve weakness due to the injection of local anesthetic either in the pretragal area or from excess anesthetic entering the middle ear and bathing a dehiscent portion of the facial nerve. This weakness should abate over 2–4 h as the medication effects dissipate. Occasionally, a patient develops a delayed paralysis 5–7 days after surgery. This paralysis is likely due to a viral reactivation within the nerve, analogous to Bell's palsy, and is treated with prednisone and an antiviral medication. In this scenario, the prognosis is excellent and the patient can expect full recovery.

Malleus and Incus Fixation

After the middle ear has been exposed, it is important to palpate the long process of the malleus and assess the mobility of the malleus, incus, and stapes. The mobility of the stapes can be evaluated with light palpation by (1) pushing the superstructure side-to-side and (2) gently pushing toward the vestibule on the long process of the incus. With experience, it is possible to appreciate partial stapes fixation and subtle abnormalities in ossicular mobility. If the stapes is mobile and the malleus or incus is fixed, the surgeon must decide whether to close the ear and recommend a hearing aid or proceed to address the ossicular fixation utilizing other standard ossiculoplasty techniques.

Perilymphatic “Gusher”

High perilymphatic outflow after performing a stapedectomy or stapedotomy is termed as perlymphatic “gusher.” Excessive perilymphatic outflow is the result of either an abnormally patent cochlear aqueduct or malformation of the lateral end of the internal auditory canal allowing for a high flow communication of intracranial cerebrospinal fluid (CSF) to the inner ear. It is more common in patients who have a congenitally fixed footplate, those with an enlarged vestibular aquaduct syndrome, or patients with mondini malformations. Given the higher prevalence of such conditions in the pediatric population, a preoperative CT scan is highly recommended for younger patients or for patients who manifest hearing loss at a young age. If these conditions are suspected preoperatively, surgery is contraindicated because of a high risk of causing complete SNHL. If this complication occurs during surgery, fat or muscle grafts may be used to seal the leak. Postoperatively, the patient should be maintained in a head-elevated position and placed on stool softeners. Severe leaks may require packing the middle ear and placing a temporary lumbar drain to reduce CSF pressure postoperatively.

Floating or Submerged Footplate

A floating or submerged footplate presents a difficult technical challenge. The footplate may become mobile during curetting due to inadvertent contact with the ossicular chain, while attempting to fracture the stapes superstructure or during manipulation of the footplate. If the footplate becomes mobile prior to the separation of the incudostapedial joint and removal of the crura, it may be best to terminate the procedure; the result may be quite satisfactory. If refixation occurs, the ear can be re-explored at a later date. If the footplate is mobilized during or after removal of the crura there are several options. The procedure can be terminated, a prosthesis can be placed on the mobile footplate, or a stapedotomy can be performed with the laser and the is operation completed. A mobile footplate presents a surgical challenge but poses little threat to the inner ear function. On the contrary, a submerged footplate places the patient at higher risk of having vestibular or cochlear dysfunction. No effort should be made to retrieve a submerged footplate from the vestibule. A graft can be placed over the oval window and a prosthesis placed.

Obliterative Otosclerosis

Obliterative otosclerosis describes the condition where excessive bony overgrowth has occurred to the point that the oval window is nearly indistinguishable from the surrounding promontory. In such cases, surgery is more difficult and the results are often less satisfying. If surgery is attempted, the obliterative bone should be removed by saucerizing (drilling on a broad front) around and over the footplate until a thin blue area is created. At this point, either a laser or drill-assisted stapedotomy may be performed and a prosthesis inserted.

Vertigo

During stapes surgery, vertigo may result from several causes including diffusion of the anesthetic agent into the labyrinth, aspiration of perilymph, manipulations within the vestibule, a displaced footplate, or the introduction of a prosthesis that may be too long. One of the advantages of using local anesthesia is that, in a patient who is awake, vertigo is readily monitored and maneuvers resulting in vertigo may be averted. A delayed onset of vertigo may be the result of a perilymphatic fistula, an excessively long prosthesis, or labyrinthitis.

Sensorineural Hearing Loss

Severe to profound SNHL is one of the most feared complications of stapes surgery and occurs in approximately 1% of patients after primary surgery and in up to 10% of patients after revision surgery. Mild to moderate losses occur more commonly, particularly in the high frequencies, but the incidence is not known.

Hearing loss may be either early or late. Possible causes of early hearing loss include intraoperative trauma, labyrinthitis, postoperative infection, granuloma formation, and a perilymphatic fistula. Patients with postoperative SNHL should be treated with a course of prednisone and antibiotics in an attempt to halt or potentially reverse losses. The cause of a delayed loss is unknown. Many surgeons prefer to wait at least 6 months and often 1 year before considering surgery on the second ear because of this risk. In addition, some patients with clinical bilateral disease may find that after their first surgery their hearing is adequate and they may forgo surgery in the contralateral ear.

Tinnitus

Most often tinnitus that is present preoperatively improves after surgery. If a SNHL has occurred due to surgery, then any existing tinnitus may worsen. Preoperative preparation for this possible complication is exceedingly important; an inadequately informed patient who develops even a mild case of postoperative SNHL and tinnitus is frequently very dissatisfied.

Incus Dislocation, Fracture, and Necrosis

If the incus is moderately mobilized, it can simply be repositioned and the integrity of the ossicular chain will be preserved. If it is truly subluxated, repositioning and terminating the procedure may result in the incus becoming stable again allowing for a standard surgical procedure in the future. Alternatively, a malleus-to-footplate prosthesis could be used. If during crimping the long process is fractured, a number of options exist. A groove can be drilled proximally along the long process and the wire crimped in this location. A shape-memory (Nitinol) prosthesis may fit well without drilling a groove. Alternately, a prosthesis designed to fit under the long process of the incus can be used. If the incus is too short, a malleus-to-footplate wire can be used. Lastly, bone cements continue to improve and may be helpful in stabilizing a prosthesis in this situation. Incus necrosis is the most common finding at revision surgery and is addressed in the same manner. The cause of incus necrosis has been ascribed to devascularization, thermal injury or, a prosthesis wire that is too tight or too loose. It is important to have available a variety of prostheses for each surgery and to be facile with different reconstructive techniques.

Loose Wire Syndrome

Loose wire syndrome may result from a lax union between the prosthesis and its connection to the incus. Patients will often complain of a “tinny” or distorted sound and they generally have a normal audiogram. Observation and reassurance is reasonable in patients with minimal symptoms however those with severe and constant symptoms, revision surgery with tightening of the wire, prosthesis replacement or fixation with cement will usually correct the problem.

The immediate success rate after stapedial surgery declines slowly over time owing to delayed CHL and potentially further SNHL. In one series reporting on primary stapedectomy cases, an air-bone gap closure of ≤10 dB was reported in 95.1% of cases after 1 year, in 94.7% after 2–5 years, and in 62.5% after 30 years. In revision cases, the reported rates of an air-bone gap closure measuring ≤10 dB was 71.1% after 1 year, 62.4% after 2–5 years, and 59.4% after 6–36 years. In a similar review, a residual air-bone gap of ≤10 dB was reported in 79% of primary cases, with a follow-up period ranging from 1 to 21 years, with a mean of 7 years. The decline in hearing after stapedotomy and stapedectomy has been estimated to occur at a rate of 3.2 dB and 9.5 dB per decade, respectively. Based on this predicted deterioration rate, it is estimated that a typical stapedectomy patient will reach the critical level of 40 dB, which will require amplification 13 years after surgery. In contrast, stapedotomy patients are not expected to reach this level for 21 years.

We would like to acknowledge Derek Kofi O. Boahene, MD for his contribution to this chapter in the previous editions.