Canal wall Down VS Canal wall Up Mastoidectomy
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🦻 Mastoidectomy: Canal Wall Up vs Canal Wall Down
Key Anatomical Landmarks
| Structure | Description | Clinical Importance |
|---|---|---|
| Aditus | Communication between middle ear and mastoid antrum | Surgical pathway |
| Posterior canal wall | Common wall between EAC (front) and mastoid antrum (back) | Decides CWU vs CWD |
| Spine of Henle | Bony projection in posterosuperior EAC | Surface landmark |
| McEwan's triangle (Suprameatal triangle) | Bounded by: supramastoid crest (superior), posterosuperior EAC line (anterior), tangent joining them (posterior) | Mastoid antrum ~1.5 cm deep |
| Facial bridge | Part of posterior bony canal wall overlying fossa incudis | Removed in Canal wall down surgery for exposure |
| Facial ridge | Posterior canal wall overlying bony facial canal | Lowered during surgery, cannot be removed fully (risk of Facial Nerve injury) |
| Anterior buttress | Junction of posterior canal wall with tegmen | Surgical landmark |
| Posterior buttress | Junction of posterior canal wall with EAC floor | Surgical landmark |
Definition of Mastoidectomy
| Term | Definition |
|---|---|
| Mastoidectomy | Surgical removal of mastoid air cells in temporal bone to eradicate disease & access middle ear cleft |
| Canal Wall Up (CWU) | Posterior canal wall preserved → mastoid cavity remains separate from EAC |
| Canal Wall Down (CWD) | Posterior canal wall removed → mastoid cavity + EAC become one large cavity |
Goals
| Procedure | Aim |
|---|---|
| Canal Wall Up (CWU) | Eradicate disease while preserving near-normal canal anatomy and hearing mechanism |
| Canal Wall Down (CWD) | Eradicate disease with wide exteriorization, ensuring a safe, dry ear |
Common Surgeries
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Cortical mastoidectomy (aka Simple/Schwartz/Complete Mastoidectomy) | Atticotomy |
| Combined approach tympanoplasty (CAT) | Atticoantrostomy |
| – | Modified radical mastoidectomy |
| – | Radical mastoidectomy |
Indications
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Limited cholesteatoma (attic/antrum only) | Extensive/recurrent cholesteatoma |
| Good Eustachian tube function | Posterior canal wall erosion |
| Reliable patient follow-up | Poor Eustachian tube function |
| Preferred first surgery (esp. children) | Unreliable follow-up |
| – | Complicated CSOM (intracranial/extracranial) |
| – | Revision surgeries |
Exposure & Clearance
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Limited exposure – sinus tympani, anterior epitympanum, hypotympanum difficult to visualize | Wide exposure – direct view of all recesses |
| Higher chance of residual disease | More complete clearance |
Recurrence
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Higher recurrence/residual disease (10–40%) | Lower recurrence (2–10%), easier detection |
Hearing Outcomes
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Better – normal canal acoustics, ossicular reconstruction easier | Poorer – large cavity, less favorable acoustics, though ossiculoplasty still possible |
Postoperative Canal Appearance
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Normal EAC preserved | Enlarged meatus with large mastoid cavity |
Cavity Care & Follow-up
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| No cavity care required; ear is self-cleansing | Lifelong periodic cleaning (aural toileting) |
| Requires strict follow-up & second-look surgery (6–18 months) | Less stringent follow-up needed |
Complications
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Higher residual/recurrent disease, retraction pocket formation | Cavity-related problems: otorrhea, granulation tissue, meatal stenosis |
Patient Limitations
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| No long-term restrictions; swimming allowed | Swimming/bathing restrictions (risk of infection, caloric vertigo) |
Auditory Rehabilitation
| Canal Wall Up (CWU) | Canal Wall Down (CWD) |
|---|---|
| Easier to fit hearing aids | Hearing aid fitting difficult due to large cavity/infections |
Advantages vs Disadvantages
| Canal Wall Up (CWU) Advantages | Canal Wall Up (CWU) Disadvantages |
|---|---|
| Preserves EAC anatomy | Limited exposure |
| Better hearing outcome | Higher recurrence (10–40%) |
| No cavity, no lifelong care | Requires second-look surgery |
| Fewer lifestyle restrictions | Retraction pocket risk if Eustachian Tube function poor |
| Preferred in children | – |
| Canal Wall Down (CWD) Advantages | Canal Wall Down (CWD) Disadvantages |
|---|---|
| Excellent exposure, complete clearance | Creates large cavity → cavity related issues |
| Lower recurrence (2–10%) | Lifelong cleaning needed |
| Recurrence easily visible | Water restrictions (no swimming) |
| No need for second look | Cosmetic deformity (enlarged meatus, postauricular hollow) |
| Useful in unreliable follow up | Worse hearing outcome, hearing aid fitting difficult |
Types of Mastoidectomy (Quick Definitions)
| Surgery | Type | Key Features |
|---|---|---|
| Cortical mastoidectomy | CWU | Exenteration of all accessible mastoid air cells; posterior canal wall intact; preserves TM & ossicles |
| Radical mastoidectomy | CWD | Removes mastoid + middle ear + attic + antrum; posterior canal wall removed; removes TM remnants, all ossicles except stapes footplate; ET opening closed |
| Modified radical mastoidectomy | CWD | Like radical but preserves TM remnants, functioning ossicles, and ET opening |
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