Mastoidectomy

Mastoidectomy

Mastoidectomy involves the surgical eradication of disease from the middle ear cleft, which includes the mastoid antrum, mastoid air cells, middle ear, and Eustachian tube. Essentially, two types of surgical techniques are employed for disease eradication: canal wall up (where the posterior canal wall is preserved) and canal wall down surgery (where the posterior canal wall is removed). The posterior canal wall is the common wall between the mastoid and the middle ear.

1. The canal wall up surgeries are cortical mastoidectomy and combined approach tympanoplasty (CAT).
2. The canal wall down surgeries include atticotomy, modified radical mastoidectomy (MRM) and radical mastoidectomy (RM).

Canal Wall Up (CWU) Surgeries.

The posterior bony ear canal wall is preserved during the CWU surgery. It is comparatively difficult to perform. The advantage of CWU is, it avoids the creation of an open mastoid cavity, thus eliminating the associated long-term cavity problems like discharge and debris accumulation. The disadvantage of CWU is, higher risk of residual disease due to incomplete visualisation of all anatomical areas. Consequently, this often necessitates a “second-look” surgery 12–18 months later to check for and remove any remaining disease.

1. Cortical Mastoidectomy (Simple Mastoidectomy or Schwartz Procedure): 🔗Read more:

2. Combined Approach Tympanoplasty (CAT): It was started by Jansen in 1960. Surgery involves cortical mastoidectomy with tympanoplasty and a posterior tympanotomy. Posterior tympanotomy is the creation of a small window in the facial recess area to inspect and remove disease from the middle ear. The facial recess approach to the middle ear is also used in the insertion of cochlear implant electrodes. Facial recess is a triangular area bounded by the facial nerve medially, the chorda tympani laterally and the fossa incudis superiorly.

 

Canal Wall Down (CWD) Surgeries.

The posterior bony ear canal wall is removed during the CWD surgery. The advantage of CWD is, it provides excellent surgical access, ensuring complete disease eradication and minimising the chance of residual disease. The disadvantage of CWD is, it creates a mastoid cavity, which can lead to lifelong problems such as persistent ear discharge, debris, and hearing loss.

1. Modified Radical Mastoidectomy (MRM). Also known as canal wall down mastoidectomy, it is the preferred surgery for atticoantral chronic otitis media with cholesteatoma. The goal of this surgery is to completely eradicate disease from the middle ear cleft and create a single, safe, and dry self-cleansing cavity, while preserving healthy middle ear structures for future reconstruction.

Indications:

1. Cholesteatoma with recurrent discharge and a good cochlear reserve for future hearing reconstruction.
2. When a canal wall up procedure is difficult due to a small, sclerotic mastoid or an inexperienced surgeon.
3. Extensive disease in only the hearing ear
4. Damaged posterior canal wall
5. Labyrinthine fistula
6. Patient is not willing to come for regular follow-up.
7. CSOM is associated with severe complications.

Contraindications

1. Benign chronic otorrhea with a central perforation and without cholesteatoma.
2. Acute otitis media with coalescent mastoiditis.
3. Persistent secretory otitis media.
4. Tubercular otitis media.

Surgical Steps:

1. Mastoid Exenteration: Initial steps are similar to cortical mastoidectomy, clearing the mastoid air cells.

2. Elevation of the tympanomeatal flap. A flap composed of the tympanic membrane and canal wall skin is elevated to expose the middle ear.

3. Removal of scutum. The lateral attic wall (scutum) is removed to ensure complete exposure of the ossicular chain, an area frequently involved in cholesteatoma

4. The bridge is broken. The bridge is the bony arch overlying the epitympanum (between the anterior and posterior buttresses), is systematically removed using a cutting burr with suction-irrigation, taking care to protect the underlying ossicles.

5. Removal of Buttresses: Both the anterior (projection of bone at the junction of the anterior bony meatal wall and epitympanic tegmen) and posterior (projection of bone at the junction of the posterior wall and the floor of the meatus) buttresses are removed to create a smooth transition from the mastoid to the external auditory canal.

6. Facial Ridge is Lowered: This is the defining and most critical step. The facial ridge (posterior canal wall, lateral to the mastoid segment of the facial nerve) is meticulously lowered with suction irrigation using a cutting burr initially and a diamond burr later, always working parallel to the fallopian canal. Avoid excessive drilling that may expose or injure the facial nerve (the most common site of injury during mastoid surgeries is this mastoid segment, specifically the second genu area). Lower the facial ridge up to the level of the lateral semicircular canal and external auditory canal floor. Concomitantly, the chorda tympani nerve is sacrificed along with the posterior wall, which results in a temporary or permanent change in taste on that side of the tongue.

7. Formation of the mastoid cavity: Adequate lowering (removal of the posterior canal wall) ensures a common cavity between the mastoid antrum and middle ear. It helps to obtain a smooth, saucerized, reverse pyramid shape cavity with no overhanging ridges. It provides adequate exposure of the middle ear structures for disease clearance. However, the downside is that a larger cavity, known as a mastoid cavity, is left behind, which can lead to long-term problems such as debris, wax, or discharge buildup.

8. Disease Clearance: All residual pathological tissue is meticulously removed from every recess of the middle ear cleft, including the epitympanum, mesotympanum, protympanum, retrotympanum, and hypotympanum. Particular attention is directed toward hidden regions such as the sino-dural angle (Citelli’s angle), sinus tympani, and facial recess. This often necessitates the use of a Buckingham mirror or an angled endoscope.

9. Reconstruction of hearing mechanism. After clearing the disease, focus on restoring the patient’s hearing. Pars tensa of the tympanic membrane and the middle ear, if healthy, are left undisturbed. If the disease extends into the middle ear, only the irreversible tissues are removed. Ossicles may be removed if diseased or partially necrosed, or if the cholesteatoma is going medial to the ossicles. In these cases, it’s impossible to clear the disease without taking out the ossicles. Reconstruction of the hearing mechanism is done. Ossiculoplasty may be done in the same sitting or as a second-stage (better results) procedure. The second stage of surgery is done after 6 to 9 months.

10. Meatoplasty: It is mandatory for all canal wall down procedures. The large mastoid cavity formed is then exteriorised by performing meatoplasty. It involves enlarging the external auditory meatus to allow for proper ventilation, drainage, and easy postoperative cleaning. A skin flap based laterally at the concha is raised from the posterior and superior ear canal walls. They then turn this flap back into the mastoid cavity to cover the area of the facial ridge, which helps in epithelization of the cavity. Sometimes, a small piece of conchal cartilage can be removed to further enlarge the opening, making it even easier to access the cavity.

11. Closure of the wound in layers is done.

12.  These entire steps of surgery are typically a “back-to-front” (posterior-to-anterior) approach. In cases with less extensive disease, a “front-to-back” (anterior-to-posterior or atticotomy) approach may be used to create a smaller cavity, which reduces the post-operative cavity problems.

Advantages of CWD Mastoidectomy (MRM & RM):

1. Complete Disease Eradication: This technique provides excellent surgical access, ensuring a high success rate for removing cholesteatoma.
2. Low Recurrence: Recurrent or residual cholesteatoma is rare because the surgeon can visualise and remove the entire disease process.
3. No Second-Look Surgery: Therefore, it avoids the need for a second operation to check for residual disease.

Complications of MRM:

1. Facial nerve injury: Facial nerve injury occurs in about 1–2% of MRM cases, most commonly at the second genu. If paralysis appears postoperatively, wait 4 hours if local anaesthesia was used. If the surgeon is not sure about the facial nerve injury during surgery, first remove the ear pack (which may be compressing the fallopian canal).  If paralysis persists, immediately explore the fallopian canal for decompression, end-to-end anastomosis or cable grafting (using greater auricular, lateral femoral cutaneous, or sural nerve). If the surgeon is confident there is no intraoperative injury, give steroids and observe for 2 weeks.
2. Horizontal semicircular canal injury: Injury to the lateral semicircular canal can occur while drilling the dural plate. Bone dust is placed over the defect, and a facial covering is placed over it.
3. Cavity problems: 20% of patients have problems of discharging mastoid cavity, which is due to either infection, high facial ridge, tympanic membrane perforation, residual disease or recurrence.
4. Sensorineural hearing loss
5. Perichondritis of pinna
6. Injury to dura
7. Injury to sigmoid sinus
8. Wound infection.

 

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