History

History is one of the most important aspects of the evaluation. Typically, with otosclerosis, hearing loss is of gradual onset and progresses slowly over several years. Approximately 70% of otosclerosis cases are bilateral and become apparent in individuals in their late teens or 20s. Hearing loss may not become apparent to the patient until age 30 or 40 years. Because most patients with otosclerosis have a conductive hearing loss, the patients report difficulty hearing conversation while chewing and may hear better in noisy rooms because of a phenomenon known as paracusis of Willis. This phenomenon is characteristic of conductive hearing loss and occurs because people speak louder in noisy surroundings. Unilateral hearing loss is less noticeable to the patient. With unilateral hearing loss, patients tend to have difficulty with direction of sound and in noisy rooms.

There is usually a positive family history of hearing loss and often of surgical correction of hearing loss. The patient usually has a negative history for infections or trauma as a possible cause of the conductive hearing loss.

Physical Examination

Physical examination includes careful otoscopy, often with the operating microscope. Pneumo-otoscopy is important to rule out middle ear serous fluid or a small perforation that could be the cause of a conductive hearing loss. There may be a red blush over the promontory or the area anterior to the oval window, known as the Schwartze sign. Tuning forks are essential for evaluation of any patient with a hearing loss¹³ because they may confirm or dispute the finding of a conductive hearing loss on audiometry.

The Weber test is performed by placing a 512-Hz fork on the center of the forehead, bridge of the nose, or anterior incisors. The Weber test lateralizes to the ear with the conductive or greater conductive hearing loss (in the case of bilateral disease). It lateralizes with 5 dB of conductive hearing loss. The Rinne test compares the patient’s perception of the relative loudness of air conduction versus bone conduction. It is performed by placing the base of a 512-Hz or 1024-Hz fork over the antrum behind the ear. The sound is compared with the loudness when the tines are placed about 2 to 3 cm from the external ear canal. The tines of the fork should be parallel with the plane of the canal. The Rinne test is sensitive and can be used to predict the degree of the conductive component of the hearing loss. When the 512-Hz fork reveals bone conduction greater than air conduction, the patient has at least a 15-dB to 20-dB conductive hearing loss. If the patient reverses the 512-Hz and 1024-Hz forks, the loss is at least 30 dB. Surgery should not be performed on a patient with a conductive hearing loss if the 512-Hz fork does not reverse.

Audiometry

The audiometric evaluation includes air conduction, bone conduction, and speech audiometry, and is usually performed by a trained audiologist. Because otosclerosis may cause unilateral conductive hearing loss, masking is important and may present problems for the tester.

The immittance audiometry battery consists of tympanometry, static compliance, and acoustic reflex testing. Immittance audiometry can be helpful in some cases of otosclerosis, confirming lack of mobility of the stapes with absent acoustic reflexes. The middle ear pressure is not affected by otosclerosis, and the tympanogram is normal with a distinct peak that occurs within the normal range. Many conditions affect the tympanogram, such as scarring of the tympanic membrane or tympanosclerosis. These conditions may coexist with otosclerosis. The peak may be lower than normal in the presence of a healthy-appearing tympanic membrane, alerting the examiner to the possible diagnosis.

Acoustic reflexes are a sensitive measure of the movement of the stapes. In the presence of otosclerosis, the reflex is absent. With early stapes fixation, the reflex may be abnormal in that there is a negative on-off effect or diphasic reflex (Fig. 144-5). With more advanced disease, the reflex is absent when the probe is in the involved ear. As the disease and hearing loss worsen, the contralateral reflex is affected as a result of the degree of conductive hearing loss in the otosclerotic ear. Hannley¹⁴ wrote an excellent article about audiologic evaluation of a patient with otosclerosis.

Figure 144-5. Progressive changes in the configuration of the acoustic reflex with stapedial fixation. A, Healthy reflex with a sustained change in compliance as long as the stimulus is on. B, Diphasic reflex with an on-off pattern. This is seen in cases of early otosclerotic stapedial fixation. C, As the stapes becomes fixed, the diphasic reflex is replaced by an absent acoustic reflex.

Small Fenestra Stapedotomy

Before surgery is considered, the risks, complications, and alternatives are thoroughly discussed with the patient. Although the risk of sensorineural hearing loss is low, the patient needs to be informed of this possibility. Total sensorineural hearing loss occurs in about 0.2% of cases, but the patient is told that there is a less than 2% chance of further hearing loss, and a less than 1% chance of losing all hearing in the operated ear. Because of the slight chance of further or total hearing loss. the poorer hearing ear is selected for surgery. We never operate on the only-hearing ear or better hearing ear.

There is a slight chance of dizziness postoperatively. This possible complication must also be discussed with the patient before surgery. Dizziness is usually transient and brief, but may persist, and in extremely rare cases could be permanent. The possibility of facial palsy is mentioned in written material, but is not discussed because of the extremely rare incidence of this complication. In a review of more than 700 stapedectomies at the House Ear Clinic, only 2 patients had transient facial weakness of delayed onset. Since the senior author has been performing small fenestra stapedectomy, he has not seen postoperative temporary facial palsy.

Surgery is usually performed as an outpatient procedure with the patient under local anesthesia. We prefer local anesthesia because (1) an awake patient can inform the surgeon if vertigo occurs, and (2) the surgery is usually of short duration with minimal discomfort and does not warrant the risks or costs of general anesthesia.

An intravenous line is placed, and the patient is given sedation with midazolam (0.5 to 2 mg) as needed; this is occasionally supplemented with intravenous morphine (2 to 4 mg). The ear is anesthetized with 1% or 2% lidocaine with epinephrine 1 : 100,000. To lessen the pain associated with the injection, 18 mL of lidocaine can be buffered with 2 mL of 7.5% bicarbonate.

The patient is placed supine on the operating table with the head turned away from the surgeon. The microscope is placed at the head of the table with the nurse standing across the table from the surgeon (Fig. 144-6). If general anesthesia is used, the anesthesiologist is seated at the foot of the table.

Figure 144-6. The operating room during stapes surgery. The nurse is on the opposite side of the patient, and the microscope is at the head of the table.

There are many variations in the basic stapedectomy technique. Any technique that produces comparably good results should be continued.

The four quadrants of the ear canal are injected at the level of the hair-bearing area. This injection works best if placed just under the skin. A fifth injection is placed in the vascular strip down to the bone. If a tissue graft is to be used, the superior postauricular area is prepared and injected. Some surgeons use a vein graft; in this case, the graft is harvested from the hand before beginning the stapes surgery.

Incisions are performed with a sickle knife (No. 1) at the lateral process of the malleus and inferiorly at about the lower one fourth of the canal extended laterally approximately 8 mm. These two incisions are connected laterally with a House canal knife (No. 2). This flap is elevated evenly from lateral to medial with a canal elevator or a round knife (Fig. 144-7). It is important to elevate all of the flap at the same time so as not to tear it. When the anulus is reached, it is carefully exposed and elevated out of its bony canal with an anulus elevator “gimmick”. Care is taken during elevation to identify the chorda tympani nerve so that it is not stretched or injured. The superior elevation is carried forward to the malleus. Care is taken not to dislocate the incus. Usually the stapes is not entirely visualized because of the bony posterior superior external auditory canal overhang. This overhang is removed with a curet; alternatively, some surgeons prefer a microdrill (Fig. 144-8). The exposure is adequate when the facial nerve can be visualized superiorly, and the pyramidal process can be visualized posteriorly.

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