Tympanomastoid Surgery: Incisions and Endoscopic Approaches

PART 1 - Types of Incisions Used in Tympanomastoid Surgery

1. Postauricular (Retroauricular) Incision

• The classical incision used for routine mastoidectomy and tympanoplasty.
• A single curved incision runs parallel to and behind the postauricular crease.
• Provides excellent exposure of the mastoid cortex, temporalis fascia, and posterior canal wall.
• When used for cochlear implants, it was the original standard but had a limitation: the incision line could overlap the implanted receiver-stimulator, risking wound breakdown. The rule of thumb is that the incision should NOT cross parallel to the device edges - if it must cross, it should do so at right angles.
• Risk: When a previous C-shaped mastoidectomy incision exists, placing a new enlarged C-shaped incision near it can create a potentially avascular area between the two incisions, leading to flap necrosis (Shambaugh Surgery of the Ear).

• Became popular in the mid-1990s, especially for cochlear implants but also applicable for revision mastoid surgery.
• Theoretical advantage: Blood flow to the postauricular skin is believed to run predominantly from inferior to superior, making an inferiorly-based flap (inverted U) better vascularized than a superiorly-based C-flap.
• Practical advantage: A previous mastoidectomy scar can be incorporated more easily into an inverted U flap than into a C-shaped incision, reducing the risk of creating avascular flap territory between old and new incisions.
• Offers the same surgical exposure as the C-shaped incision.

• A more generous postauricular incision extending further inferiorly and posteriorly.
• Used for approaches requiring wider exposure such as translabyrinthine skull base surgery, facial nerve decompression from stylomastoid foramen to geniculate ganglion, and extended procedures involving the sigmoid sinus or posterior cranial fossa.
• For translabyrinthine approach: the incision is placed approximately 4 cm posterior to the postauricular crease, allowing complete mastoidectomy and skeletonization of the sigmoid sinus.

1. Skin and subcutaneous tissue divided.
2. The Palva flap (periosteal flap) is elevated - a vascularized musculoperiosteal flap turned anteriorly over the posterior canal wall to cover the mastoid cavity if needed.
3. Subperiosteal pocket created for device placement (in cochlear implant surgery).
4. The temporalis fascia is harvested superiorly for use as a graft.
5. The mastoid cortex is exposed and drilling proceeds.

2. Endaural Incision (Lempert Incision)

• A vertical incision is placed in the suprameatal notch (between the tragus and helical crus, in the intercartilaginous area).
• A second incision extends along the roof of the bony-cartilaginous junction of the EAC.
• The two limbs join at the apex of the meatal opening.

• No visible external scar behind the ear.
• Provides direct access to the tympanic membrane, ossicular chain, and limited mastoid.
• Useful for straightforward tympanoplasty, ossiculoplasty, and limited cortical mastoidectomy.
• Faster closure and less postoperative pain.

• Limited exposure of the mastoid cortex compared to the postauricular incision.
• Not suitable for extensive mastoidectomy, radical or modified radical mastoidectomy, or skull base procedures.
• Restricted working space for the surgeon.

3. Transcanal (Meatal/Transcanalicular) Approach

• All work is done through the ear canal lumen.
• A tympanomeatal flap is elevated: a curved incision in the posterior EAC skin (at the 6 o'clock and 12 o'clock positions, 5-8 mm lateral to the annulus) raises a flap that is reflected anteriorly to expose the middle ear.
• Adequate canal diameter is essential.

• No external incision, no visible scar.
• Reduced surgical time and postoperative morbidity.
• Faster recovery, earlier discharge, less postoperative pain.
• Preferred for purely transcanal endoscopic ear surgery (TEES).

• Confined working space, especially in narrow canals.
• Cannot address mastoid disease.
• Requires skilled handling and relies heavily on endoscopic visualization.

4. Combined Postauricular + Endaural Incision

• The postauricular incision is combined with an endaural extension.
• The combined incision allows wide exposure of both the mastoid and the EAC for fashioning a large meatus in canal wall-down (open cavity) procedures.
• The inferior extension toward the mastoid tip helps with musculoperiosteal flap rotation (Palva flap) to obliterate the mastoid cavity.

The Tympanomeatal Flap (Common to Multiple Approaches)

• Tympanomeatal flap: EAC skin elevated from the annulus to expose the middle ear.
• Can be raised via transcanal, endaural, or postauricular route.
• The flap is critical for exposing the ossicular chain, middle ear mucosa, and tympanic cavity.

PART 2 - Types of Endoscopic Tympanomastoid Surgery

Background and Rationale

• Wider field of view without dead angles.
• Ability to look "around corners" using angled lenses.
• Greater magnification and image detail via modern CCD cameras.
• In vivo visualization of the middle ear in its natural, undistorted state.

• Mesotympanum: oval and round window morphology, ossicular chain.
• Epitympanum: anterior (supratubal recess) and posterior divisions, cog, tensor fold, epitympanic diaphragm.
• Protympanum: anterior tympanic cavity, bony Eustachian tube.
• Hypotympanum: inferior recess, risk of jugular bulb dehiscence.
• Retrotympanum: sinus tympani (most common site of cholesteatoma recurrence), facial sinus, lateral sinus.
• Tympanic isthmus: ventilation pathway medial to the ossicles.

Classification of Endoscopic Tympanomastoid Surgery

Type 1: Diagnostic / Inspection Endoscopy (Otoendoscopy)

• A 1.9 mm or 2.7 mm Hopkins rod endoscope is introduced through the external auditory canal.
• Can be passed transtympanically (through a myringotomy or existing perforation) or trans-EAC for meatal inspection.
• 0° scope for straight forward views; 30° scope for superior and inferior recesses.

• Pre-operative mapping of disease extent.
• Inspection of middle ear after microscopic dissection to detect residual cholesteatoma.
• Thomassin et al. demonstrated that otoendoscopy at primary canal wall-up surgery reduced residual disease at second-look from 47% to 5%.
• Ayache et al. found 44% residual disease in the epitympanum and 34% in the retrotympanum detectable by endoscopy but missed by microscopy.

• Surgeons new to endoscopy should initially look through the eyepiece directly rather than using a camera, to maintain hand-eye coordination.
• Adding a CCD camera initially creates disorientation due to working at a remote monitor - any camera rotation produces hand-eye coordination errors.
• The endoscope is passed through a slightly smaller speculum than used for microscopy to protect the EAC skin.
• The heat from a 300W light source can cause caloric-induced vertigo if the scope is left in situ >45-60 seconds; the 150W source is safer.

Type 2: Endoscope-Assisted Ear Surgery (EAES)

• Conventional postauricular or endaural incision is made.
• Mastoidectomy/tympanomastoidectomy is performed under the microscope.
• At key stages - particularly after dissection of cholesteatoma - the endoscope is introduced to inspect hidden recesses.
• A 30° or 45° angled scope is used to check the sinus tympani, anterior epitympanum, and retrotympanum.
• Residual disease found endoscopically can be removed with endoscopic instruments.

• Reduces residual cholesteatoma rates compared with microscope alone.
• Does not require mastery of endoscopic dissection techniques.
• Compatible with traditional mastoidectomy set-up.

• Requires switching between microscope and endoscope.
• The endoscope is used as an adjunct, not a replacement.

Type 3: Totally Endoscopic Ear Surgery (TEES)

• Transcanal approach only - no postauricular or endaural incision.
• A tympanomeatal flap is raised under endoscopic guidance.
• 0° endoscope for standard visualization; 30°/45° for angled recesses.
• All instruments (suction, elevators, curettes, picks, diamond drills) are introduced alongside the endoscope in the same canal.
• One hand holds the endoscope; the other operates the instrument - this is the key technical limitation (no two-handed dissection).

• Normal to generous EAC diameter.
• Disease isolated to tympanic membrane and middle ear.
• Cholesteatoma that does not extend posteriorly beyond the dome of the lateral semicircular canal.
• Adequate hemostasis achievable.

• Stenotic EAC.
• Extension of disease into the mastoid.
• Cholesteatoma extending posterior to the dome of the lateral semicircular canal (requires mastoidectomy).

• Myringoplasty / tympanoplasty.
• Ossiculoplasty.
• Cholesteatoma removal (limited, non-mastoid disease).
• Stapedectomy / stapedotomy.
• Atticotomy (transcanal endoscopic atticotomy - removal of the lateral attic wall to address epitympanic cholesteatoma).
• Type I-III tympanoplasty.
• Cartilage tympanoplasty.

• TEES results in reduced morbidity, wound complications, and greater potential to maintain normal anatomy compared with open mastoid surgery.
• Current evidence does not demonstrate a significant reduction in residual disease rates over open mastoid surgery (as of current literature).
• TEES may be particularly beneficial for visualizing middle ear ventilation pathways.
• The endoscope allows clearance under an intact ossicular chain in some cases, potentially preserving hearing better than traditional approaches.

Type 4: Endoscopic-Assisted Mastoidectomy (Hybrid Approach)

• Standard postauricular incision and mastoidectomy.
• After bony work under the microscope, the endoscope is introduced into the mastoid cavity.
• A 2.7 mm 0° or 30° endoscope surveys the mastoid cavity, aditus ad antrum, and via the posterior tympanotomy into the middle ear.
• Residual cholesteatoma not visible with the microscope can be identified and removed.

Type 5: Totally Endoscopic Ear Surgery for Cholesteatoma (TEES-Chol)

• Preoperative CT is mandatory to confirm absence of mastoid extension (posterior to the dome of the lateral semicircular canal is the cut-off point for a purely transcanal approach per Cummings).
• The sinus tympani depth (classified by Marchioni's classification) determines feasibility of endoscopic removal without mastoidectomy.
• Angled scopes (30°/45°) allow complete visualization of the retrotympanum, the most common recurrence site.
• When the cholesteatoma matrix cannot be safely dissected from the sinus tympani or stapes footplate, conversion to a combined approach (with mastoidectomy) is required.

1. Tympanomeatal flap elevation.
2. Transcanal atticotomy (if epitympanic disease) - lateral attic wall drilled out.
3. Staged removal of cholesteatoma matrix from mesotympanum, epitympanum, retrotympanum under continuous endoscopic guidance.
4. Tensor fold opening to ensure adequate epitympanic ventilation.
5. Tympanoplasty and ossicular reconstruction as needed.

Summary Table: Endoscopic Approaches

Limitations of Endoscopic Ear Surgery

1. Single-handed dissection: The endoscope occupies one hand; only one instrument can be used at a time - no two-handed dissection, unlike microscopic surgery.
2. Two-dimensional image: Standard endoscopes provide a 2D image (though 3D endoscopes are emerging).
3. Thermal risk: Heat generated by high-power light sources (300W) can cause caloric vertigo or, in prolonged exposure (>2 min in dry temporal bones), tissue temperature elevation up to 50°C. The 150W source is safer for longer procedures.
4. No mastoid access: TEES is limited to disease within the tympanic cavity; mastoid extension mandates conventional or hybrid approaches.
5. Learning curve: Requires dedicated temporal bone laboratory training before clinical application.

• Shambaugh Surgery of the Ear (Ch. 20 - Middle Ear Endoscopic Surgery; Ch. 35 - Cochlear Implant Incisions)
• Cummings Otolaryngology Head and Neck Surgery (Ch. 144 - Middle Ear Endoscopic Surgery; Totally Endoscopic Ear Surgery for Cholesteatoma)
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol. 2 (Ch. 87 - Minimally Invasive Endoscopic Tympanomastoid Surgery)