Mastoidectomy
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Direct answer
Mastoidectomy evacuates mastoid air-cell disease through the bone behind the ear, entered at Macewen's suprameatal triangle, where the antrum lies about 1.5 centimetres deep in the adult. Its three grades answer three diseases: the cortical (simple, Schwartz) operation exenterates cells while leaving the canal wall and middle ear intact, for acute coalescent mastoiditis and its subperiosteal abscess; the canal wall up (closed) procedure preserves the posterior bony wall while clearing attic and antral disease through the facial recess, keeping normal anatomy at the cost of a second look for residual cholesteatoma; and canal wall down (open, modified radical or radical) removes the wall to exteriorise the cavity, trading a dry, safe, self-monitoring ear against lifelong cavity care. Identification and preservation of the facial nerve, the horizontal semicircular canal and the tegmen are the operative constants across all three.
What you must remember
- Landmarks of entry: the suprameatal (Macewen) triangle — crest above, posterosuperior canal wall in front, tangent behind, spine of Henle as surface guide; the antrum lies about 1.5 cm deep in adults.
- Cortical (Schwartz) mastoidectomy: for acute coalescent mastoiditis — postauricular pain, sagging canal wall, Bezold abscess, facial palsy or intracranial extension not settling with antibiotics; wall and ossicles preserved.
- Canal wall up (closed cavity, combined approach tympanoplasty): intact posterior wall and normal-looking ear with better hearing rehabilitation and minimal cavity care, but residual cholesteatoma can hide behind the intact wall — planned second-look surgery or diffusion-weighted MRI surveillance is the price.
- Canal wall down (open): modified radical (Bondy) — cholesteatoma exteriorised with hearing preserved where possible; radical — drum and ossicles sacrificed, reserved for extensive or refractory disease; wide meatoplasty makes the cavity self-cleaning.
- Facial nerve: the tympanic and mastoid segments mark the dissection's floor; the horizontal canal and incus triangulate the nerve's second genu.
- Complications to quote: immediate facial palsy (explore), sensorineural deafness from labyrinth breach, vertigo, cerebrospinal fluid leak, sigmoid sinus bleeding with air embolism, and cavity discharge or recurrent cholesteatoma.
- Cavity aftercare: regular microsuction and water precautions for open cavities, with attention to meatal stenosis and a high facial ridge.
- Indications summary: cholesteatoma, complicated or non-responsive chronic otitis media, acute mastoiditis failing medical care, and access — translabyrinthine and skull base routes pass through the mastoid.
Worked example: one operation, three diseases
An eight-year-old presents with a fortnight of ear discharge that became postauricular pain, fever, a standing-out pinna and a sagging posterosuperior canal wall despite intravenous antibiotics; computed tomography shows coalescence of mastoid air cells with a subperiosteal collection. Acute coalescent mastoiditis is the cortical mastoidectomy case: a postauricular incision, burring through Macewen's triangle into the antrum, evacuating pus and necrotic cells while preserving the canal wall and ossicles, and draining the abscess. The child is usually dry and hearing-intact within weeks.
Redraw the patient as a 34-year-old with attic retraction and cholesteatoma: the choice is wall-up versus wall-down. A wall-up combined approach clears disease through the facial recess and leaves a normal ear, accepting surveillance — second-look surgery or diffusion-weighted magnetic resonance imaging — for pearls hidden behind the intact wall. Wall-down exteriorises instead: safer for extensive disease, previously operated ears, or a patient unlikely to return for review, at the price of lifelong cavity care. The decision matrix is disease extent plus expected follow-up, not surgeon preference; in every version three structures guard the floor — nerve, canal, tegmen.
Where students slip
Antibiotics alone are prescribed for coalescent mastoiditis with subperiosteal abscess when surgery is the answer. Wall-up and wall-down philosophies are swapped — wall-up preserves anatomy but needs surveillance; wall-down exteriorises at the cost of a cavity. The modified radical (Bondy) and radical operations are conflated: Bondy preserves drum and functional ossicles, the radical sacrifices them. And a discharging operated cavity is treated as expected when a wet cavity is a problem to solve.
Frequently asked questions
What is the surface landmark for entering the mastoid antrum?
Macewen's suprameatal triangle, bounded by the suprameatal crest, the posterosuperior bony canal wall and a tangent to the posterior wall, with the antrum about 1.5 centimetres deep in the adult.
When is a cortical (Schwartz) mastoidectomy indicated?
Acute coalescent mastoiditis not responding to antibiotics, with abscess, facial palsy or intracranial complications — evacuating disease while preserving wall and ossicles.
How do canal wall up and canal wall down mastoidectomy differ?
Wall-up keeps the posterior wall for better hearing but residual disease hides behind it, needing a second look; wall-down exteriorises, safer but demanding lifelong cavity care.
What is the difference between modified radical and radical mastoidectomy?
Bondy preserves the drum and functional ossicles; the radical removes them, creating a bare cavity for extensive or refractory disease.
Which structures must be identified to keep a mastoidectomy safe?
The facial nerve along its tympanic and mastoid segments, the horizontal semicircular canal, the tegmen tympani above and the sigmoid sinus behind — the four boundaries of the dissection.