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Osseous access
Access to the middle ear, antrum and mastoid for erradication of chronic ear disease and cholesteatoma is performed by drilling away bone in order to visualize these areas, erradicate the disease and reconstruct the conductive hearing mechanism.
The following are an overview of the most common approaches
1. Antrotomy: a procedure not performed commonly. It involves the drilling away of the external canal superiorly so that the attic space can be accessed. It is indicated for limited attic disease such as a well circumscribed cholesteatoma. It is contraindicated for extensive disease involving the mastoid and extending medialy in the perilabyrinthine air cells.
2. Mastoidectomy / canal wall up: in this procedure the external auditory canal wall is preserved. The cortex overlying the mastoid bone is first drilled, the tegmen, sigmoid sinus and sinodural angle are next identified and koerner's septum is entered. Once in the antrum the attic is exposed and the external auditory canal wall is thinned down. disease is removed along with the head of the malleus and incus if necessary. The middle ear space is accessed through the external auditory canal. This procedure is performed for the majority of chronic ear disease. Relative contraindications for it include previously failed canal wall up surgery with reccurent cholesteatoma, cholesteatoma in an only hearing ear and inability to ensure erradication of the disease.
3. Mastoidectomy / canal wall down: in this procedure the steps of the canal wall up mastoidectomy are performed and the canal wall is then drilled away. This approach offers the widest access of the middle ear, antrum and attic as well as the mastoid. The external auditory canal is drilled to the level of the facial nerve which is identified and left with a thin plate of bone covering it. The reconstruction in this instance would create a new middle ear space which is termed cavum minor and involves an aerated space in continuity with the eustachian tube and bound superiorly by the horizontal portion of the facial nerve and posteriorly by the vertical portion of the facial nerve. This procedure is indicated in cases of previous failed canal wall up operation with reccurent disease, in a situation of cholesteatoma in an only hearing ear and if cholesteatoma is involving areas that are difficult to access by a canal wall up procedure. In the later situation examples would be: medial extension into the perilabyrinthine air cells, extensive involvement of the oval window, fistula of the oval window, inability to erradicate the disease in the middle ear. In addition a canal wall down procedure is indicated in situations of complication from otitis.
4. Facial recess: this is an adjunctive maneuver utilized in conjunction with a canal wall up mastoidectomy. The area of bone between the mastoid portion of the facial nerve, the chorda tympani anteriorly and the short process of the incus superiorly is drilled away. It is a technically demanding maneuver that provides direct access to the middle ear from the mastoid cavity. The advantages of this are direct visualization of the facial recess, oval window niche with subsequent inceased likelyhood of erradication of cholesteatoma. In addition it provides for direct aeration of the mastoid cavity through a newly created extra anatomic conduit which is significant in a situation where the ossicles are intact in the attic and aeration through this anatomic space is questionable.
5. Radical operations: seldomly performed today. These include the creation of an completely open cavity without any grafting and total absence of the conductive mechanism short of the footplate. In this situation the eustachian tube remains open to the cavity.
6. Subtotal petrosectomy with canal wall closure. This operation is performed usually in conjunction with an approach to the skull base or petrous apex. Seldomly it can be performed for exceptionally rescidivistic or extensive cholesteatoma which has failed a radical approach in a non hearing ear.
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