Types of Mastoidectomy
There are two major types of mastoidectomy: canal wall down (CWD) and canal wall up (CWU).
Canal Wall Down Mastoidectomy
The CWD mastoidectomy is so named because the posterior (back) wall of the outer ear canal is removed during the operation. The back wall is removed to make the ear canal and the mastoid a single cavity. This single cavity is often known as the mastoid bowl. Also included in a CWD mastoidectomy is widening the opening of the outer ear canal (a procedure known as meatoplasty). The goal is to create a cavity in the ear that is open to air outside the ear. This is called exteriorizing ear disease, and it makes ear diseases such as cholesteatoma safer by allowing an easy passage of disease out of the body. This makes subsequent invasion into deeper structures of the ear and skull much less likely. A CWD mastoidectomy is often performed in conjunction with reconstruction or repair of the eardrum and/or the middle ear bones (ossicles).
Other forms of CWD mastoidectomy include a modified radical or radical mastoidectomy. With a modified radical mastoidectomy a CWD mastoidectomy alone is performed. The eardrum and middle ear bones are not touched. With a radical mastoidectomy, a CWD mastoidectomy is performed and the eardrum and middle ear bones are removed permanently. A radical mastoidectomy is performed for cases of the most severe forms of cholesteatoma.Disadvantages of Canal Wall Down Mastoidectomy
The CWD was the first type mastoidectomy, but it has some disadvantages. These disadvantages include: the need for frequent ear canal cleaning, water restrictions and possible hearing changes. The mastoid bowl or cavity created by a canal wall down mastoidectomy will often fill with earwax. The earwax must be removed periodically (approximately every 6 months) in order to prevent infection. The wide opening into the outer ear is visible, although it is not necessarily unsightly.
There are times when water must be kept out of the cavity for the persons's lifetime. Water may cause infection and it may also make a patient dizzy. Sometimes a special earplug can be made to allow swimming. At times, even the earplug is not sufficient to prevent water from entering the mastoid cavity. Scuba diving is not allowed at any time after a CWD mastoidectomy.
Another disadvantage of the CWD mastoidectomy is that the operation changes the architecture of the ear canal. Therefore, hearing may be diminished to some degree as a result in this change of architecture.
Canal Wall Up Mastoidectomy
The canal wall up (CWU) mastoidectomy was developed to address some of the limitations of CWD mastoidectomy. CWU surgery does not remove the bone of the ear canal or create a cavity that is exposed to outside air, as is done for CWD mastoidectomy. Rather, the mastoid disease along with trabeculated bone is removed and tissues are closed back to their normal positions. This eliminates the need for mastoid bowl cleaning, and people usually return to normal activities. The ear looks about the same after surgery as it did before surgery. A CWU mastoidectomy is often performed in conjunction with reconstruction or repair of the eardrum and/or the middle ear bones (ossicles).
Disadvantages of Canal Wall Up Mastoidectomy
One disadvantage of the CWU mastoidectomy is the higher chance of recurrent or residual cholesteatoma, relative to the CWD mastoidectomy. Residual or recurrent ear cholesteatoma after canal wall up mastoidectomy may be hidden from ear canal inspection in the office by the wall of the ear canal. For this reason, it is common to perform a second look surgery several months (typically 9 – 12 months) after the first surgery. The second look operation is performed to determine if there is residual or recurrent cholesteatoma that otherwise would go undetected by examination in the office and even by X-ray (CT). The reason for waiting several months after the first surgery is that, if residual or recurrent cholesteatoma is present, the cholesteatoma will often grow to a sufficient size that the cholesteatoma can be visualized surgically by 9 – 12 months. Operating too soon may mean that cholesteatoma will not have enough time to develop into a large enough size to be detectable. Waiting too long, however, increases the chance that a residual or recurrent cholesteatoma will damage the ear.
At the time of the second look operation, the surgeon reopens the middle ear and mastoid and reexamines for any recurrent disease. At the same time, the middle ear bones can be rebuilt, if it is felt that hearing could be improved.
If no cholesteatoma is found at the second look operation, no further surgery is planned. There is still a chance that chance that cholesteatoma can redevelop even if no cholesteatoma is found at the second look operation. For this reason, patients must still be followed for several years in the office to look for recurrent cholesteatoma.
If a large cholesteatoma is found at the time of the second look operation, then a canal wall down mastoidectomy is often performed. A canal wall down mastoidectomy has a lower chance of recurrent cholesteatoma than a canal wall up mastoidectomy.
© 2006 Ohio Ear Institute, LLC