Stapedectomy

History of Procedure

Hearing loss due to stapes fixation was first described by Valsalva in 1704 in his volume on the human ear. ^[1] It is unknown when the first attempts at stapes surgery were performed, although Kessel is credited as being the founder of stapes surgery in the 1870s.

Early attempts at stapes mobilization were fraught with complications, including fatal labyrinthitis, and provided hearing gain for only days. These results prompted leading otologists in 1899 at the Sixth International Otology Congress to declare stapes surgery useless, dangerous, and unethical, ^[2] thus ending further work on stapes mobilization procedures.

Following the turn of the 20th century, interest in surgery for stapes fixation was again reignited when Holmgren developed the fenestration procedure, in which a fenestra is created in the lateral semicircular canal, allowing sound to bypass the fixed stapes altogether. This was modified again by Sourdille in the 1930s, but it was Lempert who was credited with popularizing the fenestration procedure when, in 1938, he demonstrated a single-stage endaural fenestration procedure, which was quickly adopted as the procedure of choice for stapes ankylosis.

The current era of stapedectomy was started by Shea in the 1950s, when he created the first stapes prosthesis from Teflon. Various prostheses were then created during the following decade. The concept of stapes footplate surgery also changed, with various authors suggesting removing only portions of the footplate before placement of the prosthesis, and ultimately to the concept of the stapedotomy, in which a small hole is created in the fixated footplate for placement of the prosthesis. This allowed placement of the prosthesis piston into an appropriately sized hole and minimized the potential injury to the inner ear. Such techniques are still used today as the primary method of stapes surgery.

Indications and selection criteria for stapedectomy are as follows:

• Reasonably good health to tolerate anesthesia, especially if general anesthesia is needed

• Conductive hearing loss due to fixation of the stapes

• Presence of an air-bone gap of at least 15 dB across 3 frequencies confirmed with tuning-fork testing

• Good cochlear reserve as demonstrated by presence of good speech discrimination and adequate bone conduction thresholds, although this is not a universal requirement

  • Note: Stapedectomy does not treat sensorineural hearing loss (SNHL). A significant conductive component (as demonstrated by air-bone gap) is pertinent to patient selection especially when considering stapedectomy in patients with advanced otosclerosis (a patient with otosclerosis who has severely decreased speech recognition). Severe retrofenestral sclerosis and speech recognition scores of < 30% are associated with poor results. ^[3]

The ear with poorer hearing, based on the patient’s report rather than audiography, should undergo the operation first. In bilateral cases, the second ear can be operated on 6 months later, assuming this is now the poorer-hearing ear.

Contraindications to stapedectomy include the following:

• Only hearing ear with serviceable hearing

• Inner ear malformations (such as a large vestibular aqueduct and X chromosome-linked gusher)

• Poor physical health

• Current vertigo or balance problems such as active Meniere disease or especially in the case of superior semicircular canal dehiscence, in which the corresponding air-bone gap can potentially mimic otosclerosis

• A fluctuating type hearing loss

• Pre-existing tympanic membrane perforation

• Active external or middle ear infection

• An air-bone gap less than 15 dB across 3 frequencies

• Lateral ossicular chain fixation (perform ossiculoplasty or mobilize lateral chain instead of stapedectomy)

Safe and effective stapedectomy requires a thorough knowledge of the anatomy of the middle ear and proper identification of anatomical variants if present. For more information, see Ear Anatomy.

Surgery is considered successful when the air-bone gap is closed to less than 10 dB across 90% or more of frequencies with improvement in air conduction by > 20 dB and bone conduction not worsened by more than 5 dB on postoperative audiography.

Large studies of thousands of patients who have undergone stapedectomy show that the success rate generally exceeds 95% for primary cases and 50%–70% in revision cases. ^{[4, 5]}  In two large-volume studies, patients reporting concurrent tinnitus had total resolution or decrease in intensity after stapes surgery. ^{[6, 7]}

The failure rate is approximately 5%–10% overall with stapedectomy, which most commonly results from prosthesis malposition. The second most common cause of failure is necrosis of the incus. Recent reports also suggest that patients with otosclerosis are at a higher risk of sensorineural hearing loss (SNHL) than hearing loss due to presbycusis. ^[8] The authors of this article suggest continued follow-up, as most patients who undergo this procedure ultimately require auditory rehabilitation or hearing aids. ^[9]

Complications

Potential complications of stapedectomy include the following:

• Tympanic membrane perforation

• Floating or subluxed stapes footplate

• Perilymph gusher

• Facial nerve injury

• Dysgeusia

• Hearing loss

• Vertigo

• Failure of prosthesis/incus necrosis

• Granuloma formation
• Serous or suppurative labyrinthitis
• Persistent Bleeding / Persistent stapedial artery

Tympanic membrane perforation

If a small perforation occurs during surgery, a fat or fascia myringoplasty or medial graft tympanoplasty can be performed to repair the defect intraoperatively, and stapes surgery can proceed. If a larger perforation is created or encountered, the safest choice is to perform tympanoplasty only and stage the stapedectomy to a subsequent procedure.

Floating or subluxed stapes footplate

This may occur during down-fracture of the stapes superstructure when the footplate can become separated from the annular ligament that attaches it to the oval window. If this occurs, the footplate may be completely pushed into the vestibule. If the footplate does enter the vestibule, the operation should be aborted and the oval window covered with fascia and the prosthesis placed. If the footplate is not completely submerged, it can be removed with small hooks if a pre-existing control hole was made prior to attempted footplate removal. Using a laser for stapedotomy can reduce the force placed on the oval window annulus; this can allow for stapedotomy to proceed or prevent this complication. ^[10] ​ 

Once retrieved, a fascial graft and the prosthesis can be placed. An alternative is to allow the footplate to become re-fixed and then return for the placement of the prosthesis later. No attempt should be made to remove a completely submerged footplate as this has high incidence of SNHL with attempted extrication. ^[10]

Perilymph (CSF) gusher

If the cochlear aqueduct is widely patent, there may be excessive perilymph flow once the fenestration has been created. In such cases, it is usually not noted until the footplate has already been opened or removed. Usually, the flow of fluid diminishes and stops.

The head of the bed should be immediately elevated if a gusher is encountered. A fascia plug that can underlie the prosthesis should be fashioned, and this should be held in place while the prosthesis is placed. In rare cases, a lumbar drain is necessary to reduce intracranial pressure sufficiently to stop the flow of perilymph. The middle ear and external auditory canal should also be packed to reduce flow as much as possible.

Use of preoperative imaging may demonstrate anatomic anomalies increasing risk of perilymph gusher such as a connection between the subarachnoid space and the perilymph or delineate an enlarged vestibular aqueduct.  

Facial nerve injury

The facial nerve is frequently dehiscent in its tympanic segment; however, this dehiscence is on the undersurface and rarely appreciated in most cases. If the dehiscent segment is sufficiently large, the nerve may prolapse and partially cover the footplate. If this is the case, the nerve may be gently retracted superiorly in order to expose the footplate and place the prosthesis. Generally, if the prosthesis must be bent to be placed, it will not provide a satisfactory hearing result. Additionally, when the nerve is dehiscent, extreme care must be used with the laser, as the heat damage from a direct hit with the laser can lead to a facial palsy.  A potential contraindication to stapedectomy can be an anomalous facial nerve that bifurcates around the superstructure, in which mobilization superiorly cannot be performed. ^[10]   

The facial nerve monitor may aid the surgeon by providing feedback during microdissection in the vicinity of the nerve but will not eliminate the risk of facial nerve injury. Facial nerve monitoring is only conducted in cases performed under general anesthesia and is not done in cases performed under conscious sedation.  

Dysgeusia

Transient dysgeusia is common (61.9%) after stapes surgery, however, the majority of these patients (95.8%) will recover within one year.24 Taste disturbances can result from injury to the chorda tympani. During the procedure, the chorda tympani is frequently in a position that obstructs a full view of the oval window. If this is the case, the nerve can be gently retracted superiorly or inferiorly. If, however, a significant stretch or partial tear develops, the nerve should be completely severed, since patients will have shorter-lived dysgeusia if the nerve is completely sectioned rather than partially injured. Some patients report of a metallic taste on the operated side if the nerve is cut.

Unilateral chorda tympani loss is usually not a devastating injury for patients; however, in patients who will undergo bilateral middle ear surgery, great care should be taken to ensure that at least one fully functional nerve remains. Patients in whom bilateral chorda tympani have been sacrificed can suffer from dry mouth and severe taste disturbances.

Hearing loss

Sensorineural hearing loss can result from damage to the cochlea during excessive manipulation of the stapes or inadvertent injury to the cochlea. The incidence of SNHL n stapedectomy surgery is low, with large studies reporting permanent SNHL of more than 15 dB at less than 0.5%. ^[11] This incidence is slightly more common in revision cases. Generally, the only therapeutic management in such cases is amplification with hearing aids in appropriate patients.

Vertigo

Vertigo can result from excessive manipulation of the stapes during surgery. This is slightly more common in revision cases and is ascertainable only if the patient is undergoing surgery under local anesthesia. If this occurs, the patient can be treated with intravenous droperidol and ondansetron to treat the vertigo.

During laser or mechanical stapedotomy, bone fragments may become mobile and fall into the vestibule, which may increase the chances of postoperative vertigo.  Any attempts at removal of such bony fragments from within the vestibule would potentially cause severe injury to the membranous labyrinth and thus should be avoided at all costs. Vertigo due to this mechanism is typically transient, clearing within one to two months of surgery. ^[10]

Postoperative vertigo  can also be caused by a prosthesis that is too long. This cause of vertigo is typically longer lasting and dose not resolve beyond two months postoperatively. If this is the case, the prosthesis should be removed and a shorter prosthesis reimplanted. Temporal bone CT has not been shown to be an accurate method of assessing piston depth within the vestibule. ^[12]  Therefore duration of persistent postoperative, true spinning vertigo alone should be the sole indicator driving clinical decision making on whether to revise and explant a potentially problematic stapes piston. 

Failure of prosthesis

Failure of the prosthesis most commonly results from an inappropriately measured and/or crimped prosthesis. Rarely, the crimping is too tight on the incus, leading to necrosis of the end of the incus long process and displacement of the prosthesis off of the incus. If this occurs, the prosthesis must be replaced in a modified fashion farther up on the incus long process or, occasionally, on the malleus manubrium.

Granuloma formation

A rare occurrence after primary prosthesis insertion (0.07%–5%), this cause of failure is not entirely understood but is thought to be a foreign body tissue reaction, with gelfoam and fat being the most commonly implicated substances implanted within the middle ear causing their development. ^[13]  

Serous or suppurative labyrinthitis

Another uncommon complication is suppurative labyrinthitis or other surgical site infection such as acute otitis media or meningitis following stapedectomy.  Prophylactic antimicrobial therapy has not been shown to reduce the incidence of this already rare complication. ^[14]

Persistent bleeding/persistent stapedial artery (PSA)

Initial injection of anesthetic agent with diluted epinephrine (1:100,000) normally provides adequate anesthesia and vasoconstriction to perform stapedotomy.  However, otosclerotic bone and overlying mucosa may be more hyperemic during the active phase of otospongiotic bone turnover. Bleeding during the procedure is usually controlled with topical application of epinephrine on a gelfoam sponge, and hemostasis is obtained prior to placing the stapes prosthesis to provide adequate view for proper placement.  

A persistent stapedial artery (PSA) (incidence 0.02%–0.48% in general population) may provide an additional challenge during stapes surgery and if not identified prior to surgical manipulation of the stapes can lead to brisk bleeding. A PSA can also be a mimic to otosclerosis audiometrically and cause a CHL by limiting the movement of the stapes. When the artery is small in size, it can be appropriately managed by cauterization with use of bipolar cautery or diffuse mode laser, and middle ear surgery can safely proceed. ^[15]  If a larger diameter PSA is encountered, it is best left in place until it is determined through angiographic studies not to be a critical branch in CNS circulation. ^[10]