Mastoid Surgery

Cortical mastoidectomy

This is removal of air cells within the mastoid by drilling whilst maintaining the posterior wall of the ear canal. It is performed via a post-auricular incision, called a Wilde's incision, named after the famous otologist father of Oscar Wilde.

 

Indications

 

Acute mastoiditis when medical treatment has failed, occasionally for persistent discharge through a perforation to improve ventilation.

 

Risks

 

Risks of hospital admission, anaesthesia, failure of the surgery, persistent discharge, wound infection, dizziness, tinnitus, altered sense of taste, facial nerve palsy, reduction in hearing and complete loss of hearing (a dead ear - 0.5%).

Atticotomy

This procedure is used for disease that is limited to the attic (epitympanum). It can be done with the help of a microscope or purely with an endoscope according to the preference of the surgeon.

In principle, the surgery is simple. The eardrum is raised and the bone of the outer attic wall (scutum) is removed to expose the cholesteatoma. Dissection of bone proceeds upwards and backwards until the limits of the cholesteatoma sac are shown and then the disease, together with any irreparably damaged ossicles, is removed. Once removed the area is grafted with fascia or cartilage plus perichondrium and the ear drum is replaced.

Of course, surgery is rarely simple. The attic and middle ear contain very fragile and important structures that the surgeon must not damage. The distances between important structures is measured in millimetres.

Below, is a simple sequence of images that illustrate the progress of an atticotomy. There is no disease  shown in the images.

atticotomy-sequence.gif

Mastoid surgery (other)

These procedures include various approaches to treat cholesteatoma by removing diseased bone and tissue. Atticotomy (above) involves the removal of the outer attic wall, additional opening of the mastoid antrum is termed atticoantrostomy.

 

A modified radical mastoidectomy involves additional removal of the bone of the posterior ear canal. This is called a canal wall down procedure because of this. The head of the malleus and incus bone may be removed if the disease has damaged them and there will be grafting of the tympanic membrane (as in myringoplasty) and widening of the canal (meatoplasty).

The diagram below shows a modified radical mastoid cavity.  It is a left sided cavity with the eardrum shown to the left of the image and a space where the scutum and posterior canal wall should be. The cavity is self-cleaning.

Combined Approach Tympanoplasty (CAT)

A CAT is a canal wall up procedure, unlike the modified radical mastoid shown above. In a CAT the disease is approached both through a cortical mastoidectomy and a permeatal atticotomy but the wall between these (the posterior ear canal wall) is not removed.

Prior to the development of endoscopic ear surgery, the posterior parts of the middle ear would be approached by drilling a posterior tympanotomy from the cortical mastoid into the middle ear. This would allow a good view of the posterior parts of the middle ear. Since the advent of endoscopes, this is rarely necessary, as the endoscope has a better view of the posterior middle ear than a posterior tympanotomy ever did.

 

Indication for atticotomy, modified radical mastoid and CAT

Cholesteatoma. The smaller the disease the smaller the cavity will be.

 

Risks 

Risks of hospital admission, anaesthesia, failure of the surgery, persistent discharge, wound infection, dizziness, tinnitus, altered sense of taste, facial nerve palsy (1-2%), reduction in hearing and complete loss of hearing (a dead ear) (0.5%). Note that this information alone is inadequate for a full consent of the patient. there is much more involved but that is beyond the scope of your course in Swansea.