Growth Pattern of the Tympanic Ring in Human Fetuses

OBJECTIVES: The study aimed to display the growth pattern of the tympanic ring in fetal cadavers of 20-30 weeks of gestation. METHODS: In the study, 32 temporal bones of 16 fetuses (8 males, 8 females) of 24.62 ± 3.44 weeks of gestation were dissected to measure the height (TRH), width (TRW), and perimeter (TRP) of the annulus, and the width (TNW) of the opening part of the annulus at the level of the tympanic notch. RESULTS: The TRH, TRW, TRP, and TNW were measured as 8.25 ± 1.04 mm, 7.64 ± 1.08 mm, 24.93 ± 3.40 mm, and 4.01 ± 0.91 mm, respectively. The parameters were similar at the seventh and eighth months of gestation; therefore, there was no variation from the seventh month. Linear function was calculated as y = 1.328 + 0.281 x weeks (P < .001) for the TRH, y = 1.284 + 0.258 x weeks (P < .001) for the TRW, y = 3.367 + 0.876 x weeks (P < .001) for the TRP, and y = −0.603 + 0.188 x weeks (P < .001) for the TNW. CONCLUSION: The parameters (TRH, TRW, TRP, and TNW) did not alter from the seventh month in utero. The linear functions (which represent the growth pattern of the parameters) of the tympanic ring may be useful for ear professionals to guess the annulus diameters, and to diagnose growth retardation and probable congenital anomalies in utero during sonographic imaging.