title: Ontogenetic explanation for tegmen tympani dehiscence and superior semicircular canal dehiscence association.
abstract: OBJECTIVE
  To analyze the ontogeny of the superior semicircular canal and tegmen tympani and determine if there are common embryological factors explaining both associated dehiscence.
  
  
  METHODS
  We analyzed 77 human embryological series aged between 6 weeks and newborn. Preparations were serially cut and stained with Masson's trichrome technique.
  
  
  RESULTS
  The tegmental prolongation of tegmen tympani and superior semicircular canal originate from the same structure, the otic capsule, and have the same type of endochondral ossification; while the extension of the squamous prolongation of tegmen tympani runs from the temporal squama and ossification is directly of intramembranous type. The nuclei of ossification of the superior and external semicircular canals and accessory of tegmen collaborate in the ossification of the tegmental extension and by growth extend to the tegmental prolongation. This fact plus the fact that both structures share a common layer of external periosteum could explain the coexistence of lack of bone coverage in tegmen and superior semicircular canal.
  
  
  CONCLUSIONS
  The development of the semicircular canal and tegmen tympani could explain the causes of the association of both dehiscences.
authors.affiliation: Servicio de Otorrinolaringología, Hospital Universitario Miguel Servet, Zaragoza, España. Electronic address: jfraile@comz.org.
authors.forename: Jesús José
authors.initials: JJ
authors.lastname: Fraile Rodrigo
authors.affiliation: Departamento de Anatomía e Histología Humanas, Facultad de Medicina, Universidad de Zaragoza, Zaragoza, España.
authors.forename: Ana I
authors.initials: AI
authors.lastname: Cisneros
authors.affiliation: Departamento de Anatomía e Histología Humanas, Facultad de Medicina, Universidad de Zaragoza, Zaragoza, España.
authors.forename: Jesús
authors.initials: J
authors.lastname: Obón
authors.affiliation: Servicio de Anatomía Patológica, Hospital Universitario Miguel Servet, Zaragoza, España.
authors.forename: Carmen
authors.initials: C
authors.lastname: Yus
authors.affiliation: Servicio de Otorrinolaringología, Hospital de Basurto, Bilbao, España.
authors.forename: Rafael
authors.initials: R
authors.lastname: Crovetto
authors.affiliation: Departamento de Estomatología, Universidad del País Vasco, Leioa, Vizcaya, España.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Crovetto
authors.affiliation: Departamento de Anatomía e Histología Humanas, Facultad de Medicina, Universidad de Zaragoza, Zaragoza, España.
authors.forename: Jaime
authors.initials: J
authors.lastname: Whyte
mesh_terms: D004432:Ear, Middle / Q000002:abnormalities / Q000196:embryology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007759:Labyrinth Diseases / Q000196:embryology*; D010012:Osteogenesis; D010521:Periosteum / Q000002:abnormalities / Q000196:embryology; D012422:Rupture, Spontaneous; D012665:Semicircular Canals / Q000002:abnormalities / Q000196:embryology*
keywords: Bony defect; Canal semicircular superior; Defecto óseo; Dehiscencia canal semicircular superior; Dehiscencia tegmen tympani; Hueso temporal humano; Human temporal bone; Semicircular canal dehiscence; Superior semicircular canal; Tegmen tympani dehiscence