PR-5. EVALUATION OF HIGH-RESOLUTION CT USING MULTIPLANAR RECONSTRUCTION IN EXPECTING THE HEARING AFTER TYMPANOPLASTY

Takenori Miyashita, Seiko Fujiwara, Hiroshi Hoshikawa, Yoshihiro Toyama, Nozomu Mori (Kagawa University, Japan)

Objectives: The purpose of this study is to determine the value of multislice computed tomography (MSCT) using multiplanar reconstruction (MPR) image in expecting the hearing after tympanoplasty.

Materials and Methods: The relationship of preoperative MPR image findings to postoperative hearing results in 36 ears, which underwent tympanoplasty for cholesteatoma, was examined. The average air-conduction threshold and air-bone gap at 500-2000Hz were used for the assessment of pre- and post-operative hearing results. MSCT imaging was performed by Aquilion® (Toshiba Medical Systems, Tokyo, Japan).  The axial spiral scans were obtained in a helical pitch of 3.0, 0.5-mm slice thickness, 0.2-mm reconstruction interval.

Results: MPR findings of the ossicles were divided into three groups: no defect (group A), malleus and/or incus defect with no stapes defect (group B), and malleus and/or incus defect with the defect of stapedial superstructure (group C). MPR findings were in a good accordance with the operative findings of the ossicles. Tympanoplasty type I was performed for group A (3 ears), type III for group B (29 ears), and type IV for group C (4 ears). Preoperative hearing level of groups A, B, and C was 13.6±7.5dB, 49.8±18.6dB, and 60.0±22.9dB, respectively. Postoperative hearing level of groups A, B, and C was 15.6± 6.9dB, 40.0±18.8dB, and 72.1±17.4dB, respectively. There are a significant difference in pre- and post-operative hearing among all the groups (p<0.05). Based on soft shadows around the footplate of the stapes, group B was divided into 2 subgroups. Preoperative hearing level in the subgroups with no soft shadows around the footplate and with shadows was 43.3±16.9dB (n=6) and 46.2±19.6dB (n=23), respectively. Preoperative A-B gap in both subgroups was 16.9±10.0dB and 20.2±9.8dB, respectively. There was no significant difference between both subgroups. Postoperative hearing level in both subgroups was 26.7±4.7dB and 42.2±19.8dB, respectively.  Postoperative A-B gap in both subgroups was 4.2±4.2dB and 13.5±9.1dB, respectively. A-B gap was significantly decreased postoperatively in the subgroup with no shadows (P<0.05).

Conclusion:  MPR image provides precise information on the preoperative ossicular pathology. MPR findings may provide useful preoperative information for operators to choose the type of ossicular reconstruction and expect postoperative hearing results.

* Contact person email: takenori@kms.ac.jp