Stapedotomy (Endaural)

Abstract

Otosclerosis is a condition characterized by abnormal bone growth that inhibits the movement of the stapes, leading to a gradual conductive hearing loss. The treatment options encompass observation, the use of hearing aids, and surgical intervention. If the patient opts for surgery, either a stapedotomy or a stapedectomy can be executed to liberate the stapes from the sclerotic bone. In the case of a stapedotomy performed with an endaural approach, access to the middle ear is gained through a minor incision extending from the anterior ear canal to the incisura, also known as the intertragal notch. The surgeon then proceeds to remove the superstructure of the stapes, create an opening in the footplate of the stapes, and subsequently place a prosthesis into the opening, which is then connected to the incus. The outcomes of this procedure are generally positive, with 90–95% of patients experiencing an improvement in hearing.

Keywords

Conductive hearing loss; otosclerosis; stapedectomy; minimally invasive surgery; otology; air-bone gap.

Case Overview

Background

The middle ear contains three small bones known as ossicles: the malleus, incus, and stapes. These bones play a vital role in hearing by transmitting vibrations from the tympanic membrane to the oval window of the middle ear. The stapes is the smallest bone in the human body and it connects the incus to the oval window. Disruption of the conduction of vibrations from the tympanic membrane to the middle ear leads to conductive hearing loss. One potential cause of conductive hearing loss is otosclerosis, which occurs in about 10% of the Caucasian population; it is less common in the Japanese and South American populations and rare in African Americans.¹ In patients with otosclerosis, abnormal growth of bone results in stapes footplate fixation.^1-3 Stapes fixation prevents the ear’s normal conducting mechanism, leading to progressive hearing loss, tinnitus, and dizziness.¹

Treatment of otosclerosis includes observation, hearing aids, and surgery. The standard surgical intervention for otosclerosis is either complete stapes removal (stapedectomy) or footplate fenestration (stapedotomy) and replacement with a prosthetic implant.⁴ Stapes superstructure is removed and replaced by a prosthesis thus restoring conduction and hearing in both procedures. Numerous studies have demonstrated the high rates of success and long-term stability of both procedures; however, compared to stapedectomy, stapedotomy has been shown to provide better high frequency hearing improvement and lower complication rates.^4,5 Removal of the stapes can be accomplished under microscopy using lasers or micro drills. In a stapedotomy, the stapes superstructure is removed, and a fenestration is made in the footplate. A stapes prosthesis is then inserted into the fenestration and affixed to the incus.

In a stapedotomy or stapedectomy, the middle ear can be accessed by an endaural or transcanal approach.⁵ In an endaural approach, as discussed here, the stapes is accessed through an incision extending from the anterior ear canal to the incisura (intertragal notch). The postaural approach utilizes a curved incision in the postauricular sulcus. A transcanal approach uses a skin incision 8–10 mm lateral to the tympanic membrane to access the stapes, which provides limited visualization of the stapes superstructure.⁵ The selected approach is typically based on patient and surgeon preferences.

Focused History of the Patient

Patients with otosclerosis will typically present with gradually progressive hearing loss that can be either symmetric or asymmetric. Patients may also describe improved hearing in noisy environments (paracusis of Willis).⁶ Some patients may have a family history of otosclerosis, as studies have suggested an autosomal dominant inheritance pattern with variable penetrance.⁷

Physical Exam

Patients with otosclerosis will have normal external ears and normal external acoustic canals on a physical exam. Tympanic membranes will be pearly white, clear, not retracted or bulging, and without signs of inflammation. A Webber and Rinne test with a 512-Hz tuning fork will show bone conduction greater than air conduction in the affected ear, with lateralization to the side of the affected ear (negative test [abnormal]).^3,4,6 An audiogram will show conductive or mixed hearing loss ≥ 25 db across all frequencies. Additionally, assessing the acoustic reflex can be achieved by presenting an acoustically loud sound and assessing the contraction of the stapedius muscle. A positive early deflection on acoustic reflex assessment is a distinctive sign of otosclerosis. Otomicroscopy may be performed to assess the movement of the ossicles and to rule out perforation as a cause of conductive hearing loss. While otomicroscopy is an essential part of a thorough ear examination, it is not specifically used to rule out effusion. Instead, tympanometry is the preferred method to detect the presence of an effusion.³

Imaging

Temporal bone computerized tomography (CT) scans are used selectively when considering surgery in children and in patients with congenital stapes fixation.⁶ CT can also be used to rule out X-linked perilymphatic (CSF) gusher syndrome and superior semicircular canal dehiscence, which are both contraindications and not amenable to stapedotomy.⁶

Natural History

Patients with otosclerosis will typically present with progressive hearing loss that typically begins in the 4th decade of life.³ Two-thirds of patients are female, and a majority present with bilateral hearing loss.

Options for Treatment

Options for treatment of otosclerosis include observation, hearing aids to amplify audio, and surgical intervention.^3,6

Rationale for Treatment

The goal of treatment is to improve hearing, although surgery is not expected to reverse tinnitus.^3,6

Special Considerations

Patients are strongly considered for surgery if they have conductive hearing loss with negative (abnormal) Rinne test that has been shown to be secondary to stapes footplate fixation. Additionally, patients with adequate bone conduction thresholds and good speech thresholds and word recognition on audiometric testing are good surgical candidates.^3,6 Stapedotomy is contraindicated in patients with active middle ear infections, tympanic membrane perforation, inner ear malformation, or endolymphatic hydrops (Meniere’s Disease).

Discussion

Dr. John Shea was the first to perform a stapedectomy in 1959.⁴ Since its advent, innovations in techniques, prosthesis materials, and design have improved safety and outcomes. Subsequent advancements in prosthesis materials as well as the emergence of microdrills and lasers enabled surgeons to remove only a piece of the stapes and bore a small hole in the footplate in order to install a piston-shaped prosthesis, and thus the stapedotomy was created. In studies comparing stapedotomy and stapedectomy outcomes, the stapedotomy was found to provide better high frequency hearing improvement and lower complication rates.^4,5

Stapedotomy can be performed either under general or local anesthesia, depending on patient health status and preference. The patient's position is made so that the surgeon can see directly down the ear canal from a sitting position. After prepping and draping, an incision is made from the anterior ear canal to the incisura (intertragal notch), and hemostasis is achieved with bipolar cautery. Then, the bony cartilaginous junction is exposed using both blunt and sharp dissection. Soft tissue is elevated inferiorly along the subperiosteal plane using a House Lancet to create a tympanomeatal flap. Excess fascia is removed to avoid the development of a canal cholesteatoma, a collection of keratinaceous debris beneath the skin that may cause otorrhea and pain. The tympanomeatal flap is advanced to the tympanic annulus, which is then elevated to provide access to the middle ear space. Movement of the ossicles is assessed to confirm stapes fixation. A bone curette is then used to remove bone from the bony external auditory canal to provide better exposure and allow visualization of the entire ossicular chain, stapedial tendon, facial nerve, and round window. Care is taken to avoid damage to the chorda tympani, which would result in taste disturbance. The distance is measured from the footplate to the long process of the incus for prosthesis fitting. A CO₂ laser with Waveguide fiber set to a low power setting (4 W, 100-ms pulse duration) is then used to remove the posterior crus of the stapes and sever the stapedial tendon. Then, the stapedotomy is performed using either the laser or a microdrill to make an aperture in the stapes footplate. The piston of the stapes prosthesis is inserted into the stapedotomy, and the crozet is positioned over the incus and crimped into place using the laser or manual crimping if necessary. Fascia is placed into the oval window to seal it and prevent a perilymph fistula. The incision is closed and saline-soaked Gelfoam is placed along the edges of the tympanic membrane flap to maintain its position. The incision is well hidden in the intertragal notch. Total operating time is roughly 90 minutes, and blood loss is typically minimal.

Postoperatively, the patient may be discharged home on the same day or be admitted for overnight observation, depending on surgeon preference.⁶ Patients should avoid activities that cause pressure changes (nose blowing, airplane travel, SCUBA diving) and prevent water from entering their ear for 3–4 weeks. Post-op follow-up generally occurs at 1 month and 3–4 months after surgery to assess surgical site, facial nerve function, and for full audiometry. Complications from surgery include but are not limited to: sensorineural hearing loss (0.2–3%, may be profound), facial nerve damage (very rare), chorda tympani nerve damage resulting in permanent or temporary dysgeusia (30%), incus necrosis, tinnitus, vertigo, disequilibrium, serous/suppurative labyrinthitis, and reparative granuloma.^3,6,8 Nausea and vertigo can be managed with antiemetics.

Several studies have demonstrated the safety and effectiveness of the stapedotomy.^1,2,4,8 Outcomes are favorable; closure of air-bone gap within 10–15 db is achieved in 90–95% of patients. Hearing is unchanged in 10% and worse in 1%, and 1% of patients will lose hearing after surgery.³

Stapedotomy exists as a minimally-invasive surgical treatment for otosclerosis with excellent outcomes and long-term success in most patients. The endaural approach provides excellent visualization of the stapes and surrounding structures, thus optimizing safety and efficiency. Exciting advancements in technology and techniques continue to improve stapedotomy outcomes and safety, such as Laser STAMP prosthesis-free procedure that have shown promising results.⁴ In laser STAMP procedure an HGM argon laser is used to vaporize the anterior crus of the stapes and the anterior third of the footplate, ensuring complete transection and mobility of the posterior two-thirds of the footplate, followed by sealing the perilymph space with adipose tissue.¹⁰

Equipment

Special equipment for this procedure includes:^6,9

• Standard microscopic ear tray instruments.
• Laser: CO₂ or iridium.
• Microdrill: 0.6–0.8 mm.
• Stapes prosthesis: many types exist; selection is typically based on surgeon preference.
• Measuring rod: to measure the distance between the stapedial footplate and the incus.
• McGee stapes crimpers: to secure prosthesis (if a wire loop is used).

Disclosures

Author C. Scott Brown also works as editor of the Otolaryngology section of the Journal of Medical Insight.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.