title: Fetal facial nerve course in the ear region revisited.
abstract: OBJECTIVE
  The aim of this study was to re-examine the structures that determine course of the facial nerve (FN) in the fetal ear region.
  
  
  METHODS
  We used sagittal or horizontal sections of 28 human fetuses at 7-8, 12-16, and 25-37 weeks.
  
  
  RESULTS
  The FN and the chorda tympani nerve ran almost parallel until 7 weeks. The greater petrosal nerve (GPN) ran vertical to the distal FN course due to the trigeminal nerve ganglion being medial to the geniculate ganglion at 7 weeks. Afterwards, due to the radical growth of the former ganglion, the GPN became an anterior continuation of the FN. The lesser petrosal nerve ran straight, parallel to the FN at 7 weeks, but later, it started to wind along the otic capsule, possibly due to the upward invasion of the tympanic cavity epithelium. Notably, the chorda tympanic nerve origin from the FN, and the crossing between the vagus nerve branch and the FN, was located outside of the temporal bone even at 37 weeks. The second knee of the FN was not evident, in contrast to the acute anterior turn below the chorda tympanic nerve origin. In all examined fetuses, the apex of the cochlea did not face the middle cranial fossa, but the tympanic cavity.
  
  
  CONCLUSIONS
  Topographical relation among the FN and related nerves in the ear region seemed not to be established in the fetal age but after birth depending on growth of the cranial fossa.
authors.affiliation: Department of Anatomy, Histology and Embryology, Yanbian University Medical College, Yanji City, Jilin Province, China.
authors.forename: Zhe Wu
authors.initials: ZW
authors.lastname: Jin
authors.affiliation: Department of Neurology, Wonkwang University School of Medicine and Hospital, Institute of Wonkwang Medical Science, 895, Muwang-ro, Iksan-si, Jeollabuk-do, 54538, Republic of Korea. neurlogy@wonkwang.ac.kr.
authors.forename: Kwang Ho
authors.identifier: http://orcid.org/0000-0002-7751-0469
authors.initials: KH
authors.lastname: Cho
authors.affiliation: Department of Anatomy, Akita University Graduate School of Medicine, Akita, 010-8502, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Katori
authors.affiliation: Division of Internal Medicine, Iwamizawa Kojin-kai Hospital, Iwamizawa, 068-0833, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Murakami
authors.affiliation: Department of Anatomy and Human Embryology, Institute of Embryology, Complutense University, Madrid, Spain.
authors.forename: Jose Francisco
authors.initials: JF
authors.lastname: Rodríguez-Vázquez
mesh_terms: D002814:Chorda Tympani Nerve / Q000196:embryology; D003051:Cochlea / Q000196:embryology; D035301:Cranial Fossa, Middle / Q000196:embryology; D004432:Ear, Middle / Q000196:embryology; D005154:Facial Nerve / Q000196:embryology*; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D005930:Glossopharyngeal Nerve / Q000196:embryology; D006801:Humans; D013701:Temporal Bone / Q000196:embryology; D014276:Trigeminal Nerve / Q000196:embryology; D014630:Vagus Nerve / Q000196:embryology
keywords: Auricular branch of the vagus nerve; Chorda tympani nerve; Facial nerve; Genu; Greater petrosal nerve; Human fetus; Topographical anatomy