Development of the fallopian canal in humans: A morphologic and radiologicstudy

Aims: This study investigated the development of the fallopian canal with p articular reference to the mode of ossification and dehiscences, sites of i ncomplete closure around the facial nerve. Background: The precise sequence of events surrounding ossification of the tissues around the facial nerve is uncertain. Incomplete ossification resul ts in dehiscence of the adult structure, which places the nerve at increase d risk of damage from disease processes in the middle ear and iatrogenic tr auma 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 b ones from 12- to 35-week fetuses were serially microtomed to produce 7-mum slices, which were stained with hematoxylin and eosin. Quantitative and qua litative 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 sul cus, developed anteroposteriorly from the geniculate fossa to enclose the f acial nerve. The mesenchyme that formed the facial sulcus underwent endocho ndral ossification, while the bone which capped or closed the sulcus develo ped 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.