Development of the Fallopian Canal in Humans: A Morphologic and Radiologic Study

Abstract

AIMS: This study investigated the development of the fallopian canal with particular reference to the mode of ossification and dehiscences, sites of incomplete closure around the facial nerve. BACKGROUND: The precise sequence of events surrounding ossification of the tissues around the facial nerve is uncertain. Incomplete ossification results in dehiscence of the adult structure, which places the nerve at increased risk of damage from disease processes in the middle ear and iatrogenic trauma during otologic surgery. METHODS: Twenty-four temporal bones from 12-to 36-week human fetuses were resected. Eight temporal bones from 22-to 36-week fetuses were microsliced to produce 1.5-mm horizontal sections and radiographed. Sixteen temporal bones from 12-to 35-week fetuses were serially microtomed to produce 7-microm slices, which were stained with hematoxylin and eosin. Quantitative and qualitative analyses of these sections were performed to document patterns of closure of the primitive canal and dehiscence formation. RESULTS: The tympanic part of the primitive fallopian canal, the facial sulcus, developed anteroposteriorly from the geniculate fossa to enclose the facial nerve. The mesenchyme that formed the facial sulcus underwent endochondral ossification, while the bone which capped or closed the sulcus developed in membrane. In the tympanic segment, permanent congenital dehiscences were elliptical and about 1 mm in length. CONCLUSIONS: This study clarifies the mode of development of the fallopian canal, with particular reference to dehiscences, and provides a scientific basis for otologic practice.