title: The variants of the retro- and hypotympanum: an endoscopic anatomical study.
abstract: The retro- and hypotympanum are hidden areas of the middle ear, only poorly recognized. Nevertheless, this region is of relevant clinical significance, since it is regularly affected by disease such as cholesteatoma. The aim of this study is to explore and describe the anatomical variants of the hypo- and retrotympanum by the means of transcanal endoscopy. We hypothesize a significant variability of this hidden region of the middle ear. Moreover, we believe that the minimal invasive, endoscopic access is suitable since angled scopes may be used to explore the region. To this end a total of 125 middle ears (83 cadaveric dissections, 42 surgical cases) were explored by the means of 3 mm straight and angled scopes. The variants were documented photographically and tabularized. The bony crests ponticulus, subiculum and finiculus were most frequently represented as ridges. The ponticulus showed the highest variability with 38% ridge, 35% bridge and 27% incomplete presentation. The subiculum was bridge-shaped only in 8% of the cases, the finiculus in 17%. The sinus tympani had a normal configuration in 66%. A subcochlear canaliculus was detectable in 50%. The retro- and hypotympanum were classified, respectively, to the present bony crests and sinus in a novel classification type I-IV. In conclusion, we found abundant variability of the bony structures in the retro- and hypotympanum. The endoscopic access is suitable and offers thorough understanding and panoramic views of these hidden areas.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Bonali
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy. anschuetz.lukas@gmail.com.|Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, University Hospital and University of Bern, Bern, Switzerland. anschuetz.lukas@gmail.com.
authors.forename: Lukas
authors.identifier: http://orcid.org/0000-0001-6927-0664
authors.initials: L
authors.lastname: Anschuetz
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy.|Department of Biomedical Sciences, Medical School, University of Bologna, Bologna, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Fermi
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Villari
authors.affiliation: Department of Biomedical Sciences, Medical School, University of Bologna, Bologna, Italy.
authors.forename: Giulia Adalgisa
authors.initials: GA
authors.lastname: Mariani
authors.affiliation: Department of Biomedical Sciences, Medical School, University of Bologna, Bologna, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Manzoli
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Caversaccio
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy.
authors.forename: Livio
authors.initials: L
authors.lastname: Presutti
mesh_terms: D000718:Anatomy, Regional / Q000295:instrumentation / Q000379:methods; D018424:Cholesteatoma, Middle Ear / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D004432:Ear, Middle / Q000000981:diagnostic imaging / Q000473:pathology; D004724:Endoscopy / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results
keywords: Endoscopic ear surgery; Finiculus; Hypotympanum; Middle ear anatomy; Ponticulus; Retrotympanum; Sinus tympani; Subiculum