Stapedotomy

Considerations

Indications:

Progressive conductive hearing loss in setting of absent reflexes
Air-bone gap greater than 20dB in at least three frequencies
Tympanosclerosis with stapes footplate fixation
Trauma-induced footplate fracture or subluxation

Contraindications:

Tympanic membrane perforation. It is necessary that an intact tympanic membrane be present prior to stapes surgery. This helps prevent contamination of the vestibule by external ear flora. Similarly, it is recommended that patients with ventilation tubes undergo removal and healing of the tympanic membrane prior to stapedotomy
Air-bone gap less than 20dB in at least three frequencies
Meniere Disease. Relative contraindication due to increased incidence of vertigo and sensorineural hearing loss
Active external or middle ear disease
Only or better hearing ear

Physical exam:

Typically the ear examination is normal. Bilateral otomicroscopy should be performed on all patients with suspected otosclerosis. Confirmation of normal external auditory canals and healthy appearing tympanic membranes should be performed. This helps distinguish any other external or middle ear pathology as sources for possible conductive hearing loss.
Schwartz’ sign. Occasionally, slight redness may be seen beyond the tympanic membrane due to the increased vascularity over the promontory during active remodeling or otospongiosis.
Tuning fork examination is also critical. Classic findings for conductive hearing loss using 256 and 512 Hz tuning forks involve a negative Rinne in which bone conduction is greater than air conduction (classically termed “flipped forks”) and a Weber examination that lateralizes to the affected ear (if one ear has greater conductive loss than the other). These findings suggest that at least a 15 dB air-bone gap will exist on formal audiometric testing.

Audiometric findings:

Conductive hearing loss - an air bone gap of at least 20dB should be appreciated prior to offering surgery. Hearing loss less than this should prompt non-operative management and re-evaluation at a later date.
Carhart’s notch - an audiologic finding consisting of a dip in bone conduction at 2000 Hz thought to result from loss of the resonant frequency of the ossicular chain. Other conditions such as middle ear effusion and primary malleus fixation may lead to similar findings and thus Carhart’s notch is suggestive but not pathognomonic of otosclerosis
Stapedial reflexes - in cases of early otosclerosis, the stapedial reflexes may still be intact. However, presence of preserved stapedial reflexes should lead one to consider alternate diagnoses such as superior canal dehiscence where conductive loss can also be present due to a “third window” effect.

Preparation

Key anatomic landmarks:

1. Horizontal facial nerve
2. Pyramidal eminence with stapedial tendon
3. Promontory
4. Malleus/cochleariform process
5. Round window

When in view, these 5 anatomic landmarks ensure that the stapes and lenticular process of the incus are adequately visualized

Anesthesia: Local vs. general. Understanding a patient’s mobility and comorbidities may help guide the determination of local monitored anesthesia care versus general anesthesia with endotracheal intubation. In patients with poor mobility or unable to sit still for an extended period of time, then general anesthesia may prove more useful. Similarly patients who have extensive comorbidities where general anesthesia poses a greater risk, local sedation should be considered.

Local anesthesia with sedation. Benefits of this include being able to verify hearing improvement intraoperatively. Patients can also report vertigo. However, patients may startle or move during surgery. This also may not be well tolerated in patients with poor neck mobility.

General anesthesia allows for more ease of positioning and reduced the risk of unexpected movements, though also precludes intraoperative verification of prosthesis function or vertigo complications.

Positioning: Patients are typically positioned in the supine position with the head turned away, exposing the operative ear. If lateral neck rotation is limited then table tilt can be employed. Horse-shoe headrest, or a positioning bump/roll under the torso and hip on the operative side can improve access. Pad the arms and knees. If vein graft is to be taken, the contralateral hand should be positioned with padding under the wrist and fingers, exposing the dorsum of the hand. This area should be prepped and draped carefully as to not contaminate the area as the primary drape is being pulled over the body.

Perioperative antibiotics: Not indicated.

Monitoring: Facial nerve monitoring is not indicated. The risk of facial nerve injury is very low. However, if the patient is under general anesthesia, it is advisable to not use long-acting paralytics so that stimulation of the nerve would be an option if concern arose during the case.

Pre-operatively:

(Yoshi) Ensure that the vein graft is on the consent and IV is not inserted in the back of the left hand preoperatively

Procedure

Laser stapedotomy with bucket-handle prosthesis

Inject the canal with local anesthetic (lidocaine with epinephrine) using a 27g needle.
- Care should be taken to inject slowly to avoid ballooning of the skin and/or canal hematomas.
- A blanch should be seen extending down onto the tympanic membrane; this is best seen if the injection is performed under the microscope.
- Injection should be performed circumferentially (4 points), ending with the anterior canal to minimize blood dripping into the field.
Make the tympanomeatal flap incisions.
- Use the sickle knife or Beaver blade to make tangential incisions emanating from the annulus at 12 o'clock and 6 o'clock.
- Connect these with a transverse incision (usually 5-6 mm from the annulus) using a round canal knife.
- This second incision determines the flap length, which should be long enough to cover the defect that will be made after curetting the scutum.
Elevate the flap.
- Use the round canal knife to elevate the flap off the bony EAC, with the No. 3 suction in the other hand to clear any blood out of the way.
- Avoid placing the suction on the flap itself.
Pierce the middle ear mucosa posterosuperiorly with the Rosen pick, which will enter the middle ear space.
- The chorda tympani is adherent to the bony tympanic annulus here.
- Identify the chorda and separate it from the bone to allow mobilization of it for better exposure.
Continue to divide the middle ear mucosa inferiorly, thus elevating the annulus of the tympanomeatal flap.
Curette the scutum to improve exposure of the aforementioned landmarks.
- Initially, curette several millimeters posterior to the edge of the tympani annulus (leave a bony lip).
- Starting at the edge ("lip") can result in injury to the chorda or inadvertent displacement of the curette into the middle ear space with dislocation of the incus.
- Posterior curetting allows the bone to be weakened by creating a trough; the bony lip is then easily fractured off with little force.
Palpate the ossicular chain for fixation.
- Gently lift laterally on the malleus and look for movement of the incus.
- Push on the distal incus and look for compression at the incudostapedial join or for movement of the stapes.
Separate the incudostapedial joint with a joint knife or angled pick.
- Do this in a posterior to anterior direction to utilize the stabilization/counter-traction provided by the stapedius tendon.
Palpate the ossicular chain again to ensure it is the stapes that is fixed, and that the lateral chain is mobile (there can be idiopathic malleus head fixation).
Harvest a soft tissue or vein graft and allow it to dry (if performing a large stapedotomy or a stapedectomy).
- The vein graft is taken from the dorsum of the contralateral hand.
- Mark a straight vein segment without branches, and inject the area with local anesthetic.
- Make the skin incision with a 15 blade through the skin and dermis, along the axis of the vein.
- Dissect out the segment of the vein with tenotomy scissors or a curved hemostat.
- Tie off a 1 cm segment with either 4-0 Vicryl or Chromic suture.
- Clean any fat or adventitia off the vein.
- Thread it over one tyme of the tenotomy scissor and cut open the lumen.
- Lay the vein out to dry.
- Close the incision with 5-0 fast gut.
Institute laser precautions.
Test the laser on a tongue depressor to ensure the laser is focused and aligned with the aiming beam, if present, and that the burn is satisfactory.
Divide the stapedial tendon with the laser. The Bellucci scissors can be used alternatively.
Laser the posterior crus of the stapes.
Make a fenestration control hole in the stapes footplate.
- The fenestration control hole has two functions:
  - - Identify a perilymphatic gusher.
    - Second, provides an opening in which an obtuse hook can be inserted if the footplate is inadvertently mobilized.
Downfracture the stapes superstructure towards the promontony with a Rosen pick. Push the freed superstructure down onto the promontory and remove it with cupped or alligator forceps.
Measure the distance and select the desired prosthesis.
- Measuring technique varies for different prostheses.
- For the classic bucket-handle type prosthesis, measure from the vestibule to the medial edge of the incus.
- If measuring is done prior to the stapedotomy, measure from the footplate to the mid-thickness of the incus.
Make the stapedotomy.
- Enlarge the fenestration control hole with the laser in a rosette pattern (ie overlapping each subsequent laser blasts).
- This helps to prevent floating fragments of footplate bone.
- Remove the bone with a footplate pick or rasp, which can also be used to enlarge the stapedotomy.
- If there is perilymphatic fluid leaking, be gentle in suctioning this away. Do not place the finger on the hole, and only suction at the margins of the oval window.
Place the vein graft.
- Trim the graft so that the edges are clean.
- The vein graft should ideally drape onto the facial nerve and promontory. Typically, this is 5 mm x 4 mm.
- Push the vein down in the center, over the stapedotomy, to help visualize where the prosthesis should go even though the stapedotomy is now covered.
- The adventitial side of the vein interfaces with the footplate.
Alternatively, some surgeons do not use the vein graft and instead use a blood patch to seal the oval window AFTER the prosthesis has been placed.
- Apply autologous venous blood to the oval window with a 20-gauge suction tip connected to a 3 mL syringe.
- Enough blood should be applied to fill the oval window.
Place the bucket-handle prosthesis.
- Use an alligator forceps to hold the posterior lip of the bucket. The handle is resting inferiorly.
- Place the piston end into the depression made in the vein graft overlying the stapedotomy.
- Rest the bucket against the incus and remove the alligator forceps (video 135-5).
- Use the right angle hook to gently retract/stabilize the incus.
- Place the Rosen needle into the well of the bucket and gently push the prosthesis medially to slip the bucket under the lenticular process of the incus.
- Elevate the bucket handle over the distal end of the incus.
- If the bail of the handle is loose, a small piece of vein can be placed over the bucket handle to help secure it in place.
Check for the round window reflex.
Replace the tympanomeatal flap with care to ensure the edges are not curled under and that it covers the scutal defect.
Place Floxin-soaked Gelfoam over the flap.
Place a cotton ball in the meatus.

Laser stapedotomy with crimped-wire piston prosthesis

Steps 1-19 are the same.
Make the size of the fenestra 0.1 mm larger than the diameter of the piston.
The piston prostheses are sized to the bottom of the "shepherd's crook", which is the name of the portion of the wire that is crimped.
Place the piston into the fenestra.
Place the shepherd's crook over the narrowest portion of the incus.
Crimp the wire of the prosthesis over the incus; this is done with the specialized crimping instrument.
Slide the prosthesis inferiorly towards the lenticular process; the incus typically widens at this point and this result in a snug connection.
Overcrimping may lead to incus necrosis in the long term.
Nitinol-polytef (Teflon) prostheses allow heat-activated crimping of the wire. Olympus makes a version of this called the SMart 360 piston.
- Nitinol has shape memory.
- When heated, it returns to its crimped shape.
Place the autologous blood seal as described in step 19 above.

Sample Operative Report

Findings:

- All findings pertain to the LEFT side

- Stapes fixed.

- Malleus and incus mobile.

- Otosclerosis present at anterior rim of oval window.

- Facial nerve without dehiscence.

- Chorda tympani idenified and preserved.

- Performed: LEFT-sided CO2 laser stapedotomy with placement of SMart 360 piston prosthesis, 4.5 mm length

Procedure in Detail:

The patient was brought into the operating room and laid supine on the table. A time out was performed. Anesthesia was administered. The patient underwent endotracheal intubation. The head was turned to the right so that the left ear was facing upwards. The left external auditory canal was infiltrated with 2 mL of 1% lidocaine with 1:100,000 epinephrine at 4 points. The patient was then prepped and draped in a sterile fashion.

A size 7 speculum was inserted into the ear canal. The tympanic membrane was visualized and noted to be intact with normal anatomy. The sickle blade was used to make tangential incisions extending laterally from the tympanic annulus at the 12 o'clock and 6 o'clock positions. These tangential cuts were then connected with a transverse incision using a round canal knife, approximately 6 mm lateral to the annulus. The round canal knife was then used to raise the tympanomeatal flap. The middle ear mucosa was pierced with the Rosen needle and the middle ear space identified. The rest of the mucosa was divided to complete the elevation of the flap. The chorda tympani nerve was identified and preserved. The scutum was curetted to better expose the horizontal fallopian canal, oval window, stapedius tendon, and the pyramidal process. Otosclerosis was seen at the anterior rim of the oval window. The facial nerve was not dehiscent. The ossicular chain was palpated and the stapes was fixed while the lateral ossicular chain was mobile. The incudostapedial joint was separated with the joint knife. The ossicular chain was again palpated. It was confirmed that the stapes was fixed. The stapedial tendon was divided with the CO2 laser at 3 watts with 80 msec of exposure time. The posterior crus was then divided with the laser as well. The stapes superstructure was downfractured with the Rosen needle and then removed with alligator forceps. The distance from the stapes footplate to the lateral aspect of the incus was measured at 4.5 mm. The footplate fenestra was created with the CO2 laser. This was enlarged with a rosette technique. Bone fragments were removed as needed. A Smart 360 piston prosthesis was placed into the fenestra. The wire of the prosthesis was placed around the lenticular process of the incus. This was then crimped with the heat of the CO2 laser at 1 watt. Autologous blood was applied to the oval window to seal it. The round window reflex was tested and found to be present. The tympanomeatal flap was laid back down and adequately covered the scutal defect. Floxin-soaked Gelfoam was placed lateral to this. A cotton ball was placed at the external auditory canal meatus.

Anesthesia was discontinued. The patient was awakened, extubated, and then taken to the recovery room in good condition.

Post-op

General:

Patients will go home same day. Consider admission of elderly patients with poor mobility or advanced comorbidities
Avoid brisk head movements.
Avoid heavy straining/lifting or nose blowing.
Air travel should be avoided until ear is noted to be well healed.
Patients should return for follow up in one to two weeks for packing removal.
Postoperative audiogram is typically done between 1 - 3 months postoperatively; however, there can be continued mild improvement after that point.
MRI compatibility: patients should be notified of what type of prosthesis they have and the MRI compatibility for the particular prosthesis.

Medications:

PRN analgesics.
Postoperative antibiotics are not indicated.

Pearls & Pitfalls

Common Errors in Technique:

Insufficient length of the tympanomeatal flap which fails to cover the posterior bony canal wall in the setting of needed extra curettage of the scutum.
Improper exposure of the necessary landmarks may lead to increased operative time.
Mis-identifying the IS joint. Take care to feel and identify the joint space before trying to separate the IS joint. A novice mistake is to assume the IS joint is more lateral than it is, and accidentally cutting the lenticular process. This is more pertinent when a bucket prosthesis is used.
Excessive mobilization of the incus.
Inadequate crimping of wire-piston prosthesis. Failure to crimp or tighten the hook adequately can lead to mobilization of the prosthesis and erosion of the incus long process from excessive motion. Over-crimping may also lead to necrosis of the long process.
Suctioning near the vestibule. Even when there is blood in the oval window niche, the suction should be pointed away from the vestibule to remove the blood.

Complications:

Tympanic membrane perforation. If an iatrogenic perforation is small then the surgeon can consider intraoperative medial graft tympanoplasty. However, if the perforation is large, then one should consider performing only the tympanoplasty and return at a future date to complete the stapedectomy/stapedotomy so as to reduce risk of vestibular contamination.
Nerve injury. Both the chorda tympani and facial nerve are at risk during this procedure. In order to avoid injury to the chorda tympani, care should be taken with elevation of the tympanomeatal flap, annulus and entering the middle ear. Clear identification of the nerve makes injury less likely. In rare instances, the chorda tympani carries a tortuous course and may disrupt the operative view, then consideration to complete sectioning should be given. In this case, or in the case of iatrogenic injury to the nerve, care should be taken to reapproximate the nerve fibers at the conclusion of the case. Most patients will complain of temporary dysgeusia which usually resolves over the course of several months. Facial nerve injury is rare. In cases where the nerve is dehiscent or overhangs the oval window, usually fastidious technique can ensure appropriate stapedotomy without injury to the nerve.
Ossicular dislocation. Careful elevation of the tympanomeatal flap can help avoid this possible complication. Ossicular dislocation may also occur if aggressive palpation of the ossicles occurs. More commonly, this issue arises when the incus is laterally displaced during placement of the prosthesis.
Vertigo and sensorineural hearing loss. Aggressive manipulation of the stapes can result in damage to the vestibule and cochlea resulting in sensorineural hearing loss. Furthermore, misplacement of the prosthesis or excessive loss of perilymph can result in significant vertigo.
Floating stapedial footplate. This occurs as a result of down-fracture of the stapedial superstructure with resultant detachment of the remnant annular ligamentous attachment of the footplate and its displacement into the vestibule. Floating footplate can be avoided if prior to down-fracturing, a control fenestration hole is made in the footplate. The control hole facilitates extraction of the footplate if needed with a right angle hook. If a control hole was not made, drilling of the promontory may be necessary to engage large fragments of the footplate and subsequent extraction. Smaller fragments should be left in place as they rarely cause hearing loss though may contribute to positional vertigo. Multiple attempts to externalize the footplate or suctioning over the vestibule may lead to untoward outcomes including increased risk of postoperative vertigo and iatrogenic sensorineural hearing loss. If the floating stapedial footplate is not easily removed, consider applying the tissue graft and prosthesis and terminating the surgery.
Perilymphatic gusher. Occasionally a widely patent cochlear aqueduct may lead to excessive flow of perilymph after the vestibule is opened with the stapedotomy. In this case, the head of bed should be elevated to decrease flow. Some authors suggest suctioning of the fluid until the reservoir at the cerebellopontine cistern is exhausted. Ultimately, a fascia, fat or vein graft is placed over the oval window and the prosthesis positioned to hold it in place. . Rarely is a lumbar drain necessary to aid in decreasing flow postoperatively.
Reparative granuloma. This is a rare complication occurring in approximately 0.1% of cases. Typically it occurs 1-6 weeks postoperatively and can be associated with vertigo, sensorineural hearing loss and roaring tinnitus. Treatment options include steroids and antibiotics vs. exploratory surgery in which the granulation tissue, prosthesis and graft (if used) are removed and replaced.