Volume of the epitympanum and blockage of the tympanic isthmus in chronic otitis media: A human temporal bone study

HYPOTHESIS: To compare the differences in the epitympanic bony volume and the area of the tympanic isthmus (TI) in human temporal bones (HTBs) with chronic otitis media (COM) having epitympanic involvement and those without COM. BACKGROUND: TI is crucial for mastoid and epitympanic ventilation. Previous studies demonstrated that the area of TI was related to the degree of HTBs pneumatization and that COM caused suppressed pneumatization of the middle ear, decreasing volume. To our knowledge, there have been no studies, however, investigating the correlation between COM and epitympanic volume or between the TI and the epitympanic volume. METHODS: Eleven HTBs from children with COM and 11 HTBs without COM (control group) were examined. Three-dimensional models were generated from HTB histopathologic slides with reconstruction software (AMIRA), and epitympanic bony volumes were measured and compared between the two groups.The narrowest aerated/bony TI area was also measured and compared to investigate the correlation between the bony epitympanic volume and the TI area within each group. RESULTS: There were no significant differences in epitympanic bony volume or bony TI area between the groups. Aerated TI area in the COM group was significantly smaller than that in the control group (p < 0.01). There was no relationship between aerated TI area and bony epitympanic volume in the two groups. In the COM group, there was a negative correlation between bony TI area and epitympanic volume (p < 0.001). CONCLUSION: This study suggests that congenital or developmental stenosis of the TI may not be associated with epitympanic pathology, but blockage of TI with soft tissue pathology may be associated with chronic tissue pathology in COM.