High-resolution computed tomography: determination of the cause of pediatric sensorineural hearing loss.

High-resolution computed tomograms (HRCT) reveal strikingly little variation in the dimensions of inner ear structures among people with normal hearing. However, a subgroup of people exist who have a sensorineural hearing loss (SNHL) and morphologically normal HRCT scans, yet have subtle radiographic aberrations based on measurements of inner ear dimensions. These changes might have resulted from teratogenic influences during the late first to mid second trimester, a time when the inner ear has achieved adult form, yet continues to enlarge to adult size. A retrospective study of HRCTs on three groups of ears was performed to determine inner ear structure dimensions. Group I, the control group, consisted of 50 ears with no SNHL and no discernible abnormalities on HRCT. In group II, there were 70 ears with SNHL and obvious abnormalities on HRCT. Group III, the test group, was composed of 140 ears with SNHL and "normal" HRCTs. Groups II and III were analyzed, applying the normal dimensions derived from group I. When compared to the control group (I), all of the ears in group II were abnormal. Moreover, 75% of the ears in group III had subtle differences not apparent unless measurements were made. Two or more abnormal dimensions were found in 32%. Findings and implications are thoroughly discussed.