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Monday, July 28, 2008

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Introduction
Mastoid exploration is usually carried out  to remove  Cholesteatoma from the middle ear and mastoid areas of the temporal bone (the bone containing the ear). Cholesteatoma is a sac of skin which erodes the bone surrounding the ear and may damage hearing, balance and the nerve which supplies the muscles of the face. The sac usually arises from the upper part of the ear drum. Often the problem starts as a small dimple or pocket on the ear drum which gradually enlarges and eventually forms an erosive sac. The aim of the operation is the give a safe, dry and hearing ear by excising the cholesteatoma sac and reconstructing the hearing mechanism. There are two types of operation which attempt to achieve this.

Combined approach tympanoplasty (CAT)
Combined approach tympanoplasty attempts to remove the disease by  viewing the middle ear and mastoid through the ear canal and mastoid bone. After the cholesteatoma sac is removed, the bone of the ear canal is preserved and the ear drum restored to its normal position. This procedure therefore preserves normal anatomy and some argue that hearing is better, the ear is more likely to be dry after the operation, there are no swimming restrictions and once the ear is deemed clean of disease no further care is required. The disadvantage is that very small pieces of cholesteatoma may be left behind as it can be difficult to observe all the recesses where it can hide (the otoendoscope has reduced this problem) and for this reason a second operation is always required to ensure the ear is truly free of disease. This usually takes place at 6-12 months after the first procedure. If the ear is clean the bones of hearing are reconstructed to enhance hearing. If at the second operation some residual disease remains, it is removed and  a further operation is performed 6-12 later.

Modified radical mastoidectomy (MRM)
In a modified radical mastoidectomy the normal structure of the ear is not maintained. Again the mastoid bone is drilled away, the middle ear observed through the ear canal and cholesteatoma disease removed. Here, however, to enable good clearance of disease the back wall of the ear canal is drilled away, the eardrum is partially removed and the patient is left with a mastoid cavity  which may be viewed through the ear canal in the clinic. In this procedure access to the disease is very good and usually all is removed. Any left behind will grow out rather than in anyway, and therefore usually only a single operation is required to render the ear safe. Some argue that discharge from the ear after this procedure is higher than with a CAT and that hearing results are not so good but this is by no means certain. After this operation follow-up in the clinic at least at yearly intervals will be required forever to keep the mastoid cavity clean.