Hintergrund Low-set ears are frequently associated with chromosomal disorders, malformations
and genetic and non-genetic syndromes. They present a feature that is typically described
in postnatal clinical exams or in genetic or paediatric textbooks for different congenital
diseases. In a prenatal setting “low set ears” are a diagnosis that is usually made
by ultrasound experts and their subjective evaluation. Standardized measurements or
definitions are lacking. The aim of this study was to evaluate and compare ear metrics
and a systematic ear-eye angle measurement approach in normal fetuses and in fetuses
with a known genetic or non-genetic syndrome/malformation in 3D volumes of the fetal
ear.
Methoden This is retrospective study based on stored 3D ultrasound volumes of the fetal head
collected during routine exams in the second and third trimester. The “ear-eye angle”
and the length of the ear were measured by two trained examiners in healthy fetuses
and in fetuses with malformation or a genetic or non-genetic syndrome. To avoid measurement-bias,
the outcome was blinded to the examiners.
Ergebnisse We compared 40 ears of postnatal confirmed healthy fetuses with five cases of fetuses
with a genetic syndrome or malformation (syndrome group). The 3D ear image was taken
at a median of 21 weeks' gestation (17-32). On average, the ears of the fetuses
with chromosomal abnormalities were lower-set with a larger ear- eye angle of 4.25°
(2,66°-7,88°) compared to the control group of 1.26° ( -8,5°- 7,5°). The length of
the ears between fetuses from the syndrome group and fetuses from the control group
was a median of 14,8mm (11,3- 17,8mm) and 14,5 (8,3- 24,6mm).
Schlussfolgerung Systematic evaluation of the fetal ear on routinely collected 3D volumes is feasible
and can be standardized. In this small sample size of collected normal and abnormal
fetuses the median ear-eye angle is larger compared to the control group while the
ear length was very similar. Further evaluation with a larger sample size is need.
