Prenatal ultrasonography diagnosis of fetal microtia with tympanic ring agenesis: a case report.

Microtia is frequently accompanied by middle ear anomalies, among which absence of the tympanic ring is relatively rare and seldom diagnosed prenatally. Previous reports have mainly focused on external ear anomalies, with limited experience in the prenatal diagnosis and postnatal verification of middle ear osseous abnormalities.We report a case of fetal microtia complicated by absence of the tympanic ring diagnosed by prenatal ultrasound. A systematic examination at 24 weeks of gestation revealed abnormal unilateral auricular morphology, with size and shape inconsistent with a normal fetus at the same gestational age; normal auricular structures were poorly visualized, and the external auditory canal was not clearly demonstrated. On the affected side, the middle ear tympanic ring was not visualized, with absence of its ossification center, suggesting microtia complicated by absence of the tympanic ring. After prenatal counseling, the woman chose to terminate the pregnancy. Post-induction CT confirmed findings consistent with prenatal ultrasound.This case verifies at the histological level that the external and middle ear share a common origin, and demonstrates that prenatal ultrasound can clearly display fetal external and middle ear structures, holding important clinical value for diagnosing microtia with absence of the tympanic ring. Recognition of the ultrasound features of tympanic ring absence may improve prenatal detection and provide a reliable basis for perinatal management and genetic counseling. Prenatal ultrasound is an effective method for diagnosing fetal microtia and assessing concomitant absence of the tympanic ring, helping improve prenatal recognition of occult middle ear anomalies and reduce missed diagnoses. This study clarifies the diagnostic value of postnatal CT verification and provides new practical evidence for the prenatal diagnostic pathway of such congenital anomalies.