Superior Canal Dehiscence Patients Have Smaller Mastoid Volume than Age- and Sex-Matched Otosclerosis and Temporal Bone Fracture Patients

BACKGROUND AND OBJECTIVES The purpose of the study was to compare the mastoid air-cell volume of the patients with superior semicircular canal dehiscence syndrome (SCDS) and that of the control patients with otosclerosis and temporal bone (TB) fracture. SUBJECTS AND METHODS Ten patients with SCDS were enrolled and 10 patients with bilateral otosclerosis and TB fracture were selected as control groups by age and sex matching. To measure the mastoid air-cell volume, 3D reconstruction software was used. RESULTS In 10 patients with SCDS, the mean age was 44.5 years, ranging from 16 to 79 years (M : F=4 : 6). Mean mastoid air-cell volume in the SCDS side was 3319.9 mm(3), whereas 4177.2 mm(3) in the normal side (p=0.022). Mean mastoid air-cell volume in the right side of otosclerosis patients was 6594.3 mm(3) and it was not different from 6380.5 mm(3) in the left side (p=0.445). Mean mastoid air-cell volume in normal side of TB fracture was 6477.2 mm(3). The mastoid air-cell volume in the SCDS side was significantly smaller than that of otosclerosis and TB fracture patients (p=0.009, p=0.002, respectively). The mastoid air-cell volume in the normal side of SCDS was significantly smaller than that of TB fracture (p=0.019), but not significant with that of otosclerosis (p=0.063). CONCLUSIONS Our findings revealed that the mastoid air-cell volume in the SCDS side was significantly smaller than control group, which suggest that the decreased mastoid pneumatization is closely related to the generation of SCDS.