Three-Dimensional Development of the Facial Nerve Path through the Ear Region in Human Embryos

Abstract

The goal was to determine how the facial nerve path forms normally through the ear region. Five three-dimensional computer reconstructions and eight wax plate—graphic, two-dimensional reconstructions were made from a group of 47 serially sectioned human embryos that were in the blastemal period of ear development, when most of the definitive arrangement is established. The size, shape, and positional changes of the facial nerve relative to the external ear and notochord were studied in both lateral and frontal views. The vertical (dorsoventral) position of the external ear region remains constant but shifts caudally. After formation, the geniculate ganglion assumes a position that gradually becomes rostrodorsal to the external ear. Facial nerve branches form and grow into regions expanding peripherally. The superficial petrosal branch appears to hold the ganglion in position as the horizontal segment of the facial nerve forms when the external ear shifts caudally. Possible growth movements explaining abnormal nerve paths are discussed.

Keywords

embryonic development facial nerve human ear pathway

Get full access to this article

View all access options for this article.

References

Fowler

Jr . Variations in the temporal bone course of the facial nerve. Laryngoscope 1961;71: 937–46.

Proctor

Nager

. The facial canal: normal anatomy, variations and anomalies. Ann Otol Rhinol Laryngol 1982;91 (Suppl 97):33–61.

Müller

O'Rahilly

. The human chondrocranium at the end of the embryonic period proper, with particular reference to the nervous system. Am J Anat 1980;159: 33–58.

O'Rahilly

. The timing and sequence of events in the development of the human eye and ear during the embryonic period proper. Anat Embryol (Berl) 1983;168: 87–99.

Gasser

. The development of the facial nerve in man. Ann Otol Rhinol Laryngol 1967;76: 37–56.

McClean

Prothero

. Coordinated three-dimensional reconstruction from serial sections at macroscopic and microscopic levels of resolution: the human heart. Anat Rec 1987;219: 434–9.

O'Rahilly

Müller

. Developmental stages in human embryos. Carnegie Institution of Washington publication 637. Meriden, Conn: Meriden-Stinehour Press, 1987: 140–257.

Gasser

. Early formation of the basicranium in man. In: Bosma

, ed. Symposium on Development of the Basicranium. DHEW Publication No. (NIH) 76–989. Bethesda, Md: US Department of Health, Education and Welfare, 1976: 29–43.

Patten

Philpott

. The shrinkage of embryos in the processes preparatory to sectioning. Anat Rec 1921;20: 393–413.

10.

Rabl

. Über das Gebiet des Nervus facialis. Anat Anz 1887;2: 219–27.

11.

His

. Zur Entwicklungsgeschichte des Acustico-Facialgebietes beim Menschen. Arch Anat Entwicklungsgesch 1889: 1–28.

12.

Popowsky

. Zur Entwicklungsgeschichte des N. facialis beim Menschen. Morphol Jahrb 1895;23: 329–74.

13.

Futamura

. Über die Entwicklung der Facialismuskulatur des Menschen. Anat Heft 1906;30: 433–516.

14.

Streeter

. On the development of the membranous labyrinth and the acoustic and facial nerves in the human embryo. Am J Anat 1907;6: 139–65.

15.

Pearson

. The roots of the facial nerve in human embryos and fetuses. J Comp Neurol 1947;87: 139–59.

16.

Gasser

. The early development of the parotid gland around the facial nerve and its branches in man. Anat Rec 1970;167: 63–78.

17.

Sataloff

. Embryology of the facial nerve and its clinical applications. Laryngoscope 1990;100: 969–84.

18.

Streeter

. Development of the auricle in the human embryo. Carneg Conrrib Embryol 1922;14: 111–38.

19.

Aghemo

Fortunato

. Observations on the development of the auricle in man. Panminerva Med 1969;11: 10–2.

20.

Gerhardt

Otto

H-D

. The intratemporal course of the facial nerve and its influence on the development of the ossicular chain. Acta Otolaryngol (Stockh) 1981;91: 567–73.

21.

Gasser

Hendrickx

. The development of the facial nerve in baboon embryos (Papio sp.). J Comp Neurol 1967;129: 203–17.

22.

Padget

. The development of the cranial arteries in the human embryo. Carneg Contrib Embryol 1948;32: 205–71.

23.

Camero

. A correlation of the developing face with the developing brain in human embryos between the fourth and eighth weeks of gestation using 3-dimensional computer reconstruction [Thesis]. New Orleans, La: Lousiana State University Medical Center School of Graduate Studies, 1992.