Chapter 15

The problem of stapedial fixation was identified in the 1860s.1 Many authors considered the implications of the fixation, including those who bypassed (fenestration)² and those who mobilized³ the stapes. The basic principles of stapedectomy were defined in 1958 with John Shea’s⁴ description of removal of the stapes and replacement of the stapes with a prosthesis. Controversy continues to exist over the best type of prosthesis, the ideal place and way to anchor the prosthesis, the importance of the stapedius tendon, the amount of the footplate to remove, the material to use to seal the oval window, and other details. The important observation is that the vast majority of stapedectomy operations are successful.⁵

Because the anatomy of the oval window tends to be consistent from case to case, and the steps of stapedectomy are well defined, each portion of the operation lends itself well to study. Thus, in stapedectomy, each portion of the operation has been studied and optimized in different ways. Surgeons have been able to define success using an optimal technique that works well in their hands.

PATIENT PRESENTATION AND INITIAL EXAMINATION

Patients present with the primary complaint of hearing loss. The hearing loss usually develops insidiously between puberty and the age of 30. Often, patients delay seeking assistance for 2 or 3 years.⁶

The family history may or may not be positive for hearing loss treated by surgery. Numerous authors in reviewing their experience have found that about 50% of patients have a positive family history.^7,8 A sibling of a patient with otosclerosis has only about a 1 in 10 chance of developing otosclerosis.⁹ In spite of the changing population of the United States, these statistics have changed little over many years.

The physical examination of the ear is normal. In most patients with stapedial fixation today, there are no physical findings of note. The external ear, the canal, and the drum are all completely normal. In years past, Schwartze’s sign could be seen; that is, through the tympanic membrane, a red hue of engorged blood vessels leading to an active metabolic focus of otosclerosis could be seen. Such a finding today is rare, because most disease is seen at an earlier stage.

Otosclerosis, the disease of bone that seems to cause the stapes to be fixed in the narrow oval window niche, continues to be a disease of many faces. Histologically, the disease affects 10 times more people than have clinical evidence of disease. The histologic picture is that of a basophilic focus of remodeling bone occasionally involving the cochlea and the balance canals. The occurrence of this remodeling process in endochondral bone makes otosclerosis unique. The etiology of the disease remains obscure with several theories being predominant. The first, that otosclerosis is an inherited disease, has been held for many years.10 Genetic analysis has shed some light on the possible etiology of this situation. By comparing the components of the abnormal type I collagen gene found in osteo-genesis imperfecta, with the genes found in the collagen of otosclerosis, common sequences were found, suggesting a common genetic link.¹¹ The second, that otosclerosis may be an immunologic reaction to a measles virus insult, is of more recent origin.¹² Modern genetic and immunohistochemical data support both etiologies.

AUDIOLOGY

There are three audiometric profiles in otosclerosis. The first is that of a progressive sensorineural hearing loss. It may be possible for these individuals to have had a small air bone gap at some point in the past, and that gap to have resolved over time. The loss is typically progressive over a period of several decades. Such a loss can eventually result in a profound and complete hearing loss.

The second pattern of presentation is with a conductive hearing loss. In a conductive hearing loss, there has been gradual encroachment of the otosclerotic focus of bone onto the stapes. The encroachment can occur at the anterior arch or the footplate at the annulus. As there is more encroachment, the conductive hearing loss becomes greater, until a maximum conductive hearing loss is reached. Thus, a 50-dB hearing loss suggests a great deal of fixation of the footplate.

Finally, the two types of hearing loss can present together as a mixed hearing loss. That is, an individual can present with both a sensorineural hearing loss and a conductive component to their hearing loss, the combination of the two yielding the total mixed hearing loss. Carhart¹³ noted an over-correction of the hearing in many patients operated for otosclerosis. The exact mechanism of this improvement is unknown; therefore, predicting which patients will benefit in this way is difficult. Relying on such a response may prove disappointing to physician and patient.

IMPEDANCE AUDIOMETRY

Tympanometric findings are characteristic. The ear is most compliant at normal pressures, but the degree of compliance is reduced because of the ossicular fixation. Thus, the tympanogram appears relatively flat, with maximal compliance at zero pressure. The acoustic reflex patterns can be diagnostic in oto-sclerosis. If the stapes is firmly fixed, the reflexes will be absent. Early in the disease, the stapes will be only slightly fixed, and a biphasic “on-off” response will be elicited at the onset and the offset of the stimulus. If symptoms are present less than 5 years, 94% of patients will show the effect. Between 5 and 10 years, only 50% show the effect, and after 10 years, virtually no patients will show the effect.¹⁴

PATIENT SELECTION

The patient considered for stapedectomy should have two appropriately masked audiograms to confirm adequate bone thresholds and an air bone gap in excess of 15 dB. The conductive loss must be confirmed with a reversed (bone conduction greater than air conduction) 512-Hz tuning fork, and a Weber test that lateralizes to the affected ear. The acoustic reflexes will be absent or demonstrate the on-off effect. Concomitant pathology is excluded by examination.

The poorer-hearing ear is appropriately selected for intervention. When hearing levels are similar and one ear had been previously operated, the unoperated ear should be treated rather than revising an ear. The surgery will be easier, the benefits greater, and the patient will generally be happier.

Rarely, a patient presents with otosclerosis in an only hearing ear. Much thought and consideration should be given to the decision to operate. Although one should rarely, if ever, operate on an only hearing ear, maintenance of communication and stabilization of hearing are important considerations in otosclerosis, which tends to be a progressive disease. Thus, there may be a rare patient for whom surgery might be considered in an only hearing ear. These cases should be attempted only by very experienced surgeons, and even then with trepidation.

Speech discrimination should be adequate. With a pure conductive loss, discrimination will improve to 100% if the stimulus can be made loud enough. Patients should be in reasonable health, although advanced age is not a contraindication to surgery. Stapedectomy in very young children (younger than 5 years of age) may be contraindicated until it is demonstrated that they are not prone to otitis media. The benefits of surgery for both children and the elderly have been demonstrated.15,16

Stapedectomy can be beneficial in patients with far-advanced otosclerosis. These patients have a severe or profound mixed loss. Surgery may raise their thresholds into the aidable range, when pre-viously a hearing aid could not be worn. Typically they have excellent speech production and air conduction no better than 95 dB with bony thresholds in excess of 60 to 75 dB (the limit of the audiometer). The conductive element may be detectable with the 512-Hz tuning fork applied to the teeth when it is not heard on the mastoid. The upper central incisors and the alveolar ridge give an 11-dB gain over applying the fork to the mastoid. The examiner must be sure that the fork is heard and not felt by the patient.¹⁷

ALTERNATE THERAPIES

SODIUM FLUORIDE THERAPY

Sodium fluoride supplements with calcium and vitamin D have been prescribed as a measure to prevent further hearing loss when it is diagnosed. Unfortunately, documentary proof of the treatment effectiveness has been scanty.¹⁸ Because of anecdotal evidence, however, it may be appropriate to continue to prescribe the over-the-counter medication. A course of sodium fluoride (as Fluorical, two tablets twice daily for 2 years) is used.

HEARING AIDS

Any patient who will benefit from a stapedectomy will also benefit from a hearing aid. This alternative must be offered to the patient.¹⁹ Many patients elect to try a hearing aid, but after considering the convenience of surgery versus the convenience of hearing aids, they elect to return for further consultation for surgery.

OBSERVATION

Occasionally, patients elect merely to observe their hearing loss. This can occur for many reasons, including lack of insurance coverage, other commitments, and fear. Gentle reassurance and supportive observation generally guide the patient back to the office at a later date.

CONTRAINDICATIONS

Infectious ear disease is a contraindication to surgery. This includes diseases of the middle and external ear. The presence of external otitis or a respiratory tract infection is cause to delay surgery pending resolution of the problem. Either problem can result in entry of bacteria or viruses into the inner ear with a potentially disastrous result. Meniere’s syndrome poses a potential contraindication. The dilated saccule may sit immediately beneath the footplate and be damaged upon opening the vestibule.²⁰

The patient’s occupation is not a contraindication to surgery. Six active-duty fighter pilots have been operated, as well as a ballerina, and they continued to perform their duties.²¹ As with any surgery, however, patients should be fully informed about the potential complications as well as the benefits of surgery.

OPERATING ROOM SETUP AND PATIENT POSITIONING

It is important to perform all stapes surgery under local anesthesia with sedation. This permits less postoperative nausea and a shorter stay. Additionally, patients can inform the surgical team of any intraoperative nausea or vertigo. In revision surgery, vertigo can inform the team of adhesions between the prosthesis and the saccule, preventing complications. As a final benefit, intraoperative audiometry can be completed, allowing perfect adjustment of the prosthesis during surgery.²²

The patient is premedicated with midazolam 1 mg IV (Versed) 1 hour prior to surgery. Upon arrival in the operating room, an air threshold audiogram is completed by the operating room nurse and compared with the results from the office. Intravenous sedation with propofol (Diprivan or Brevital) is accomplished to provide amnesia and sedation during the ear canal injections. A four-quadrant injection with lidocaine 2% with 1:10,000 epinephrine is completed. The ear is prepared with povidone iodine and any remaining prep solution is irrigated from the ear by the surgeon.

An appropriately sized speculum is introduced into the ear and rotated to dilate the ear canal. The short process of the malleus should just be visible in the speculum. Patient position should be adjusted at this point to provide an easy view of the malleus and the posterior half of the eardrum. Often, a small amount of head-down positioning with the chin moved to the contralateral shoulder suffices. A final injection of the lidocaine solution is made into the vascular strip, permitting a small amount of hydro-dissection of the flap. A speculum holder facilitates the remainder of the procedure.

The surgeon sits behind the patient with the ear to be operated positioned up. The anesthetist sits across from the surgeon, allowing him or her to provide consolation for the patient and to assess the ongoing level of sedation. The scrub nurse can stand on either side of the surgeon, using his or her Mayo stand to hold the necessary instruments, and be at the surgeon’s dominant hand.

What material to use for grafting the open oval window has been widely discussed. Blood, fascia, vein, and other tissues have been described. A study in the 1960s addressed the idea of the characteristics of the ideal grafting material.23 Fascia and vein are comparable in metabolic rate. Vein creates a very thin membrane. Thick fascia may be difficult to mold to the shape of the oval window. Loose areolar connective tissue “moon glue” is one of the more ideal tissues, being composed of fascia, but more malleable.²⁴

THE INCISION

Stay updated, free articles. Join our Telegram channel

Join