The Developmental Origin of the Auricula Revisited

Abstract

Objectives/Hypothesis: Congenital auricular anomalies are common. Additionally, the auricle plays an important role in the staging of human embryos. However, little is known about the embryological development of the auricle. The most commonly reproduced developmental theory by His (1885) describes six hillocks; three on the first and three on the second pharyngeal arch. The aim of this study was to assess the validity of this theory by modern techniques and to expand the knowledge of the embryological development and morphology of the auricle. Study Design: 22 human embryos from the Carnegie collection between Carnegie stage 13 and 23 (28–60 days) were selected based on their histological quality. Methods: Histological sections of the selected embryos were examined. Three-dimensional (3D) reconstructions were prepared. Additionally, literature research was performed. Results: The hillocks were absent in most stages. Contrary to common knowledge, the auricle is almost entirely innervated by branches of the facial nerve. The branches of the trigeminal nerve only innervate the tragus and the anterior external auditory meatus (EAM). Consequently, this indicates that almost the entire auricle is derived from the second pharyngeal arch, with the exception of the tragus and the anterior EAM. Conclusions: The 3D reconstructions show the anatomy and development of the auricle to be different from concepts presented in current textbooks. As a consequence, we propose that preauricular sinuses should be classified as first pharyngeal arch anomalies. Level of Evidence: NA Laryngoscope, 130:2467–2474, 2020.