urgical findings at the time of operation for recurrent cholesteatoma are the same as those at the time of primary operation, suggesting that same pathogenesis for cholesteatoma persists even after the primary operation. In 1983, the author invented anterior tympanotomy (AT) for the treatment of recurrent cholesteatoma. This procedure includes the removal of the anterior attic bony plate following intact canal wall mastoidectomy. Since then, we have begun a study to assess AT as a procedure to lower the rate of cholesteatoma recurrence and to confirm the hypothesis that the anterior attic bony plate is one of the pathogenesis of middle ear cholesteatoma.
This report consists of the following three parts:
1. Basic and clinical studies of the protympanum
a) In order to emphasize the role of the protympanic cavity in middle ear pathology, comparative anatomy of the middle ear cleft using several kinds of mammals were studied.
b) Thee mbryologicanl anatomy of human temporal bones was studied by three-dimensional graphic reconstruction. The developing frmo of 4 pouches described by Proctor was modified. We only found a gently sloping bony prominence which later develops into the anterior attic bony plate, and a shallow depression which develops into the supratubarl recess.
c) From the histological study of the temporal bone of neonates and infandts, we found that the supratubal recess and the anterior attic bony plate develop during the process of pyramidal bone pneumatization.
d) Clinical anatomy of the protympanum was studied in the following ways:
i) Osseous stenosis of the Eustachian tube was surgically treated by the musculotubal canal approach and satisfactory results were obtained.
ii) Cases of extensive cholesteatoma involving the internal carotid, the cochlea and the facial nerve were demonstrated.
iii) The anterior tympanic spine and the malleal anterior spine occasionally fix to each other in chronic otitis media, causing increased conductive deafness. For the treatment of this condition, a new surgical approach of anterior spinotomy was devised and the diagnostic criteria for this method was indicated. Statistical study showed that tympanoplasty with anterior spinotomy significantly improved hearing level, especially in the lower frequencies.
iv) In order to evaluate tensor tympani muscle function, poststapedectomy otosclerosis patients were examined using the aural reflex test. No significant positive response was obtained.
v) Anatomical measurements were done of the supratubal recess, the anterior attic bony plate and the intratympanic mucosal folds in adult temporal bones, providing better surgical anatomical knowledge useful for AT.
vi) The tensor tympani mucosal fold and the anterior attic mucosal fold were also electronmicroscopically studied. These folds were easily distinguished from each other by their width.
vii) A very interesting case of congenital conductive deafness was reported in which the anterior attic bony plate fused with the malleus head indicating their possible relationship in the embryonic stage.
viii) CT and MRI of the temporal bone, especially of the cases of cholesteatoma, were studied and their clinical usefulness was emphasized.
2. Results of anterior tympanotomy in cholesteatoma surgery.
The rate of true recurrence, not of residual or transplanted recurrences, was compared between the AT group (cases operated on with AT) and the non AT group (cases operated on without AT). Two types of cholesteatoma, attic type cholesteatoma and adhesive type cholesteatoma, were studied separately.

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