Anatomical feature of the middle cranial fossa in fetal periods: Possible etiology of superior canal dehiscence syndrome

Abstract

Conclusion: Different from adults, the superior semicircular canal (SSC) protrudes into the cranium during the fetal period. This might cause adhesion of the membranous labyrinth to dura as the bony labyrinth develops much later than the membranous labyrinth. This adhesion interferes with ossification and leads to a bony defect in the SSC. Objectives: The purpose of this study was to investigate a possible etiology of superior canal dehiscence syndrome (SCDS) from a view point of ontogeny. Methods: Forty-two adult cadavers and 4 fetal cadavers were used for macroscopic observation of the middle cranial fossa (MCF). In addition, six fetuses underwent computed tomography (CT) examinations. The volume data of the CT obtained from four adults were also used for comparison. Using these CT data, we investigated the anatomic relationship between the MCF and SSC. Results: The SSC and the cochlea in fetuses protruded into the cranium in macroscopic anatomy and CT examination. On the other hand, the SSC of all adults was completely or mostly buried in the temporal bone.

Keywords::

• Fetus
• hearing loss
• superior semicircular canal
• vertigo

Acknowledgment

Fetus sections were provided courtesy of the Evolutionary Anatomy in the Research Department of Cell and Developmental Biology, University College London. The authors deeply appreciate Professor Keiichi Akita, Dr Kumiko Yamaguchi, Clinical Anatomy, Tokyo Medical and Dental University, and Professor Fred Spoor, Evolutionary Anatomy in the Research Department of Cell and Developmental Biology, University College London for providing fetus specimens. The study was supported in part by Grants-in-Aid for Scientific Research (nos 22659305, 21390459, 23390399) from the Ministry of Science, Education, Sports and Culture of Japan, and by Health and Labour Sciences Research Grants (H23-005; Researches on Sensory and Communicative Disorders, and H23-021; Research on Measures for Intractable Diseases) from the Ministry of Health, Labour and Welfare of Japan.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.