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SHORT ABSTRACT
Anatomy of the Temporal
Bone Illustrated by
Pathological Cases
CORRESPONDING AUTHOR:
Isabelle Delpierre
Hopital Erasme and Hopital
des Enfants Reine Fabiola, BE
isabelle.delpierre@erasme.ulb.
ac.be
KEYWORDS:
Temporal bone Anatomy
TO CITE THIS ARTICLE:
Delpierre I. Anatomy of the
Temporal Bone Illustrated by
Pathological Cases. Journal
of the Belgian Society of
Radiology. 2022; 106(1):
118, 1–3. DOI: https://doi.
org/10.5334/jbsr.2959
ISABELLE DELPIERRE
ABSTRACT
Abstract for the BSR Annual Meeting.
2Delpierre Journal of the Belgian Society of Radiology DOI: 10.5334/jbsr.2959
The temporal bone is composed of three bony parts: the
petrous part, the squamous part, and the tympanic part.
This bone contributes to the calvarium and to the skull
base formation.
The squamous portion (SP) is thin and shell-like,
located between the sphenoid, the parietal, and the
occipital bones. The horizontal component of the SP
participates in the formation of the zygomatic arch and
set up the roof of the glenoid fossa and of the external
auditory canal. It also forms the lateral part of the
antrum. The vertical component of the SP is convex,
laterally located to the temporal lobe of the brain and
serves as attachment to the temporalis muscle.
The tympanic portion is a U-shape bone opening at
the top, forming the most important part of the bony
external auditory canal.
The petrous portion has a pyramid shape (petrous
pyramid). The apex of the pyramid is forward and medially
located and the base is laterally positioned. Inferiorly, the
petrous part has relationships with the vasculonervous
structures (entrance of carotid canal, aperture of
tympanic canal [of Jacobson], jugular foramen, inferior
opening of the facial canal). The petrous pyramid contains
the inner ear. The posteromedian surface contains the
porus acousticus (opening of the internal auditory canal
for the vestibulocochlear and facial nerves), and the
vestibular and cochlear aqueducts. The anterior surface
of the petrous pyramid forms the tegmen tympani which
is the roof of the tympanic cavity.
The analysis of the temporal bone must be systematic
to avoid forgetting to analyse some structures. One way
could be to check the anatomical structures from the
external to the internal part of this bone.
The external auditory canal is formed by a fibrocartilage
part laterally and a bony part medially, closed by the
tympanic membrane. This membrane is attached to the
scutum superiorly (arising from the squamous part) and
to the tympanic bone inferiorly.
The middle ear (also called tympanic cavity) is divided
into three compartments: the epitympanum (or attic),
the mesotympanum (at the level of the tympanic
membrane), and the hypotympanum. This cavity is
connected to the nasopharynx via the Eustachian tube.
The roof of this cavity is the tegmen tympani, separating
this area from the middle cranial fossa. The anterior wall
of the cavity corresponds to the carotid canal. The medial
wall is related to the bony covering of the inner ear (by
the petrous bone) and of the tympanic portion of the
facial nerve. More posterosuperiorly there is the area of
the aditus.
The tympanic cavity contains three ossicles from
lateral to medial: the malleus, the incus, and the stapes,
and also two muscles: the tensor tympani and the
stapedius muscle.
The inner ear is formed by a bony labyrinth enclosing
a membranous labyrinth and a perilymphatic space.
The bony labyrinth consists of a cochlea, a vestibule,
three semicircular canals, and the cochlear and vestibular
aqueducts.
The cochlea is a spiral structure of two and a half turns
around a central conical bony axis called the modiolus.
The osseous spiral lamina, continued by the basilar
membrane, divides the spiral structure of the cochlea
in two parts, the scala tympani and the scala vestibuli,
communicating at the apex by the helicotrema. The
basal turn opens posteriorly by the round window in the
round window niche.
The vestibule is an ovoid structure in relation with
the middle ear by the oval window. The three semicircular
canals are the superior, the posterior and the lateral
canals. These canals are related to the vestibule.
The membranous labyrinth contains endolymph.
It consists of the utricule and saccule located in the
vestibule, semicircular channels and the cochlear canal
in the cochlea.
The internal auditory canal (IAC) contains the facial
nerve (VIIth nerve), anteriorly and superiorly located,
and the branches of the vestibulocochlear nerve (VIIIth
nerve). The cochlear branch is anteriorly and inferiorly
located, and the superior and inferior vestibular branches
are posteriorly located in the IAC.
The cochlear branch of the VIIIth nerve enters into the
modiolus.
The facial nerve enters the facial nerve canal, formed
by three parts. The first is a short labyrinthine segment
curling anteriorly across the superior part of the labyrinth
up to the geniculate ganglion in the geniculate fossa.
There, the orientation of the nerve changes (first genu) to
run posteriorly and laterally along the medial wall of the
middle ear: it is the tympanic segment of the facial nerve,
just below the lateral semicircular canal and above the oval
window. The course of the nerve changes again (second
genu) at the level of the sinus tympani to run vertically: it
is the mastoid segment of the VIIth nerve. The facial nerve
exits the skull base through the stylomastoid foramen.
During the presentation, the temporal bone anatomy
will be illustrated by some representative pathological
cases.
COMPETING INTERESTS
The author has no competing interests to declare.
AUTHOR AFFILIATIONS
Isabelle Delpierre orcid.org/0000-0001-9435-5475
Hopital Erasme, DE
3Delpierre Journal of the Belgian Society of Radiology DOI: 10.5334/jbsr.2959
TO CITE THIS ARTICLE:
Delpierre I. Anatomy of the Temporal Bone Illustrated by Pathological Cases. Journal of the Belgian Society of Radiology. 2022; 106(1):
118, 1–3. DOI: https://doi.org/10.5334/jbsr.2959
Submitted: 30 September 2022 Accepted: 03 October 2022 Published: 18 November 2022
COPYRIGHT:
© 2022 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0
International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original
author and source are credited. See http://creativecommons.org/licenses/by/4.0/.
Journal of the Belgian Society of Radiology is a peer-reviewed open access journal published by Ubiquity Press.