2. Anatomy of temporal bone
Location
The temporal bone is
situated on the sides and
the base of the cranium
and lateral to the temporal
lobe of cerebrum.
7. Borders / Sutures
Occipitomastoid suture
separates occipital bone and mastoid
portion of temporal bone.
Squamosal suture separates parietal
bone and squamos portion of temporal bone.
8. Sphenosquamosal suture
separates sphenoid bone and squamos portion
of temporal bone.
Zygomaticotemporal suture
separates zygomatic bone and zygomatic
process of temporal bone.
9. External acoustic meatus
Cartilaginous lateral portion
Funnel-shaped
The cartilaginous portion is
continuous with the auricle, flexible
and surrounded by fat.
Osseous medial portion
Surrounded by the tympanic
portion of the temporal bone
Two thirds of the length of the
EAC
Covered by skin and periosteum
only.
10. Middle Ear Cavity
Air space within the petrous portion of the temporal bone
between the eustachian canal anteriorly and the mastoid air cells
posteriorly
Laterally - TM
Medially - Otic capsule and cochlear promontory
Superiorly- Tegmen tympani
Inferiorly - Jugular floor
Subdivided into three spaces
hypotympanum
mesotympanum
epitympanum
11. Mastoid antrum is located in the
anterosuperior part of the mastoid
portion of the temporal bone and
communicates with the epitympanum
via a narrow channel termed the
aditus ad antrum.
The antrum is surrounded by smaller
variable-sized mastoid air cells
The mastoid air cells are divided by
Koerner’s septum a thin bony structure
formed by the petrosquamous suture
that extends posteriorly from the
epitympanum, into medial and lateral
components.
Mastoid
12. Ossicles
Suspended by the TM, the ossicular ligaments to the epitympanic
walls, and the oval window.
The manubrium and lateral process of the malleus attach to the TM.
The neck of the malleus is connected to the tensor tympani tendon .The
circular head of the malleus articulates with the triangular body of the
incus.
The short process of the incus projects posteriorly and is suspended
within the epitympanic space, pointing toward the aditus ad antrum.
The long process of the incus projects inferiorly, parallel to and behind
the manubrium of the malleus. The tip of the long process bends
medially to end in the lenticular process, which articulates with the
head of the stapes
13. The stapes consists of the head, two crura, and a footplate .
The footplate of the stapes attaches to the oval window of the
vestibule and is secured by the annular ligament.
14. Inner Ear
petrous portion of the temporal bone.
osseous labyrinth - consists of the cochlea,
vestibule, and SCCs.
osseous labyrinth encapsulates the
membranous labyrinth, which contains
endolymph and is surrounded by perilymph.
15. Internal Auditory Canal
Bony conduit within the petrous portion of the
temporal bone .
Transmits VII (facial) and VIII (vestibulocochlear) from
the pontomedullary junction of the brainstem across the
cerebellopontine angle (CPA) cistern to the inner ear .
The IACs should be nearly symmetric. Although there is
wide variation in the exact shape and size of the canals,
asymmetry of greater than 2 mm suggests pathology.
16. The IAC is partially divided by a transverse bony crest called the
crista falciformis which runs parallel to the long axis of the canal and
divides it into a superior and inferior portion.
A vertical crest termed Bill’s bar divides the superior component into
anterior and posterior parts. The facial nerve is located in
anterosuperior compartment, the cochlear nerve in the
anteroinferior compartment, and the superior and inferior vestibular
nerves in the posterosuperior and posteroinferior compartments,
respectively
17. Carotid Canal
The carotid canal enters
the base of the skull, ascends
vertically, then turns
horizontally and medially
toward the petrous apex
This canal lies anterior
and inferior to the cochlea
and is separated from the
middle ear cavity by a thin
bony plate.
18. Jugular Foramen and Fossa
The jugular foramen is divided
smaller anteromedial neural
compartment (pars nervosa) containing
cranial nerves IX, X, and XI
larger posterolateral vascular
compartment (the pars vascularis)
containing the jugular vein.
The floor of the tympanic cavity
normally forms the roof of the jugular
fossa.
19. FACIAL NERVE
Facial nerve (VII cranial) consists of a motor and
sensory root, the latter is also known as the nervous
intermedius
NUCLEI OF ORIGIN
Three brainstem nuclei contribute to the facial nerve: one motor,
one secretomotor, and one sensory:
Facial nerve nucleus in the pons as the motor fibres of the
facial nerve loop posteriorly over the abducens nerve nucleus,
they form the facial colliculus in the floor of fourth ventricle
Superior salivary nucleus next to the facial nucleus supplies
secretomotor parasympathetic fibres
Nucleus of tractus solitaris lateral to the dorsal nucleus of
the vagus nerve supplies taste fibres that eventually end up in
the chorda tympani
20. COURSE
Course of the facial nerve may be divided by the
stylomastoid foramen into intracranial- intrapetrous part and
extracranial part
21.
22. INTRACRANIAL - INTRAPETROSAL PART
Intracranial (cisternal) segment - zero branches
Meatal (canalicular) segment (internal auditory canal): 8 mm
long, zero branches
Labyrinthine segment (IAC to geniculate ganglion): 3-4 mm
long, 3 branches (from geniculate ganglion)
Tympanic segment (from geniculate ganglion to pyramidal
eminence): 8-11 mm long, zero branches
Mastoid segment (from pyramidal eminence to stylomastoid
foramen): 8-14 mm long, 3 branches
23. Intracranial (cisternal) segment
The nerve emerges immediately
beneath the pons, lateral to
the abducens nerve and medial to
the vestibulocochlear nerve and is
joined by the nervus intermedius,
which has emerged lateral to the
main trunk.
Together the two travel laterally
through the cerebellopontine
angle to the internal acoustic
meatus.
The cisternal segment has no
branches.
24. Meatal (canalicular) segment
Having been joined by
the nervus intermedius,they are
located in the anterior superior
quadrant of the internal auditory
canal, above the falciform crest
and anterior to Bill's bar.
The meatal segment has no
branches.
25. Labyrinthine segment
As the facial nerve and nervus
intermedius pass through the
anterior superior quadrant of
the internal acoustic meatusit enters
the Fallopian canal passing
anterolaterally between and superior
to the cochlea(anterior)
and vestibule(posterior), and then
bends posteriorly (the anterior or first
genu) at the geniculate
ganglionwhere the nervus
intermedius joins the facial nerve and
where fibers for tte synapse .
26. three branches originate:
greater superficial petrosal nerve
lesser petrosal nerve
external petrosal nerve
shortest only measuring 3-4 mm
narrowest and the most susceptible to vascular compromise
27.
28. Tympanic segment
As the nerve passes posteriorly
from the geniculate ganglion it
becomes the tympanic segment (8-
11 mm in length) and is
immediately beneath the lateral
semicircular canal in the medial
wall of the middle ear cavity.
The nerve passes posterior to
the cochleariform process, tensor
tympani and oval window Just
distal to the pyramidal eminence
the nerve makes a second turn
(posterior or second genu) passing
vertically downwards as the
mastoid segment.
The tympanic segment has no
branches.
29. Mastoid segment
Measures 8-14 mm in length
Extends from the posterior genu
to the stylomastoid foramen
It runs in the medial wall of the
aditus ad antrum of the mastoid.
It gives off three branches
Nerve to stapedius
Chorda tympani terminal branch
of the nervus intermedius
Nerve from the auricular branch
of the vagus nerve (CN X)
30.
31. Extra-temporal segment
As the nerve exits the stylomastoid foramen,
Sensory branch that supplies part of the external acoustic
meatus and tympanic membrane.
Muscular branches - Passes between the posterior belly of
the digastric muscle and the stylohyoid muscle, supplying both
and then enters the parotid gland.
Lying between the deep and superficial lobes of the gland the
nerve divides into two main branches at the pes anserinus -
superior temporofacial and inferior cervicofacial branches.
From the anterior border of the gland, five branches emerge
Temporal
Zygomatic
Buccal
Mandibular (marginal)
Cervical
33. The facial nerve is the only cranial nerve that may
show normal post-contrast enhancement.
Typically enhancement is seen:
Anterior genu (geniculate ganglion)
Posterior genu (between tympanic and mastoid segments)
Some enhancement can also be seen in the labrynthine,
tympanic and mastoid segments.
Proximal greater superfical petrosal nerve
No enhancement should be seen in:
o Cisternal segment (that in the cerebellopontine angle)
o Meatal segment (that in the internal acoustic meatus)
o Extracranial segment (beyond the stylomastoid foramen)
34. TEMPORAL BONE IMAGING TECHNIQUES
CT and MRI are currently the most widely used techniques for
imaging the temporal bone.
Each technique has advantages and disadvantages, and often
more than one examination is necessary for a complete temporal bone
evaluation.
CT
Excellent for assessing the osseous structures of the temporal bone
Not ideal for evaluating the soft tissue contents of the otic capsule,
brain, or vessels.
MRI
Characterizing the cerebrospinal fluid (CSF), brain, and cranial nerves.
36. The carotid canal lies just anterior to the jugular fossa, forming a “snowman”-
like configuration.
Both demonstrate sharp cortical margins. Inferiorly only a small spine, the
caroticojugular spine, separates the two as they converge to enter the carotid sheath.
The descending facial nerve canal is lateral to the jugular foramen, seen as a
rounded well-corticated lucency.
The mandibular condyle and TMJ can also be seen.
Jugular foramen level.
37. EAC - Anterior and posterior walls of
the bony demonstrate dense, sharp
cortical margins without soft tissue
covering. The anterior margin of the EAC
forms the posterior lip of the TMJ.
Cochlear aqueduct - Medial funnel-
shaped opening seen as a triangular
lucency facing the CPA, progressively
enlarging from lateral to medial. The
opening of the aqueduct may be large
and mimic the IAC.
The descending facial nerve canal is
easily identified posterior to the EAC.
The petrooccipital fissure separates
the temporal bone from the occiput.
Inferior tympanic level
38. The carotid canal can be seen early in
its anteromedial course through the skull
base, parallel and medial to the tensor
tympani muscle at this level.
The tensor tympani muscle is lateral
and parallel to the carotid canal
The normally thin TM may be visible.
The descending facial nerve canal can
be seen just posterior to the pyramidal
eminence.
The vestibular aqueduct is seen as a
thin bony lucency along the posterior
margin of the temporal bone, near its
opening to the posterior cranial fossa.
Midtympanic level
39. The manubrium of the malleus
parallels the TM.The manubrium of
the malleus lies parallel and anterior
to the long process of the incus.
Along the posterior wall of the
middle ear is the pyramidal eminence,
with the facial nerve recess lateral and
the sinus tympani medial to the
eminence.
The descending facial nerve canal
can be seen just posterior to the
pyramidal eminence.
Facial
nerve
recess
Sinus
tympaniDescending
VII nerve
canal
40. The stapedial superstructure (head, crura, and tympanic portion of
the footplate) is often seen, forming an arch over the oval window.
The stapes suprastructure is medial to the incus
The apical, middle, and basal cochlear turns are seen at this level
along with the round window niche at the basal turn.
41. The crura of the stapes can be seen
extending toward the oval window
Tensor tympani tendon can be seen
making a 90-degree turn and attaching
to the neck of the malleus.
Epitympanic–internal auditory canal level
42. Round head of the malleus and the
triangular body and short process of the incus
are seen in their characteristic “ice cream
cone” configuration.
The IAC is slightly funnel-shaped and ends
in an ovoid fundus.
The canals for the facial nerve, cochlear
nerve, superior vestibular nerve, and inferior
vestibular nerve (singular canal) can be seen
leaving the fundus of the IAC.
Tympanic segment is seen coursing along
the medial wall of the tympanic cavity
43. The modiolus and interscalar
septae of the cochlea are visualized
posterolateral to the cochlea.
44. The lateral SCC is seen protruding into the middle ear.
The labyrinthine segment of the facial nerve canal
(fallopian canal) can be seen extending to the anterior genu,
and the tympanic segment is seen coursing along the medial
wall of the tympanic cavity.
45. The aditus and antrum is situated between the epitympanum and
mastoid antrum.
The mastoid antrum lies posterior and lateral to the aditus ad
antrum and opens into many mastoid air cells.
The posterior SCC and common crus of the posterior and superior
SCCs can be seen.
More superiorly the superior SCC is present.
Mastoid antrum level
47. Coronal temporomandibular joint level
The horizontal carotid canal is seen as an oval structure just
lateral to petrooccipital suture.
The semicanal for the tensor tympani muscle is seen as a small
lucency lateral to the carotid canal.
The air-filled eustachian tube is inferior to the tensor tympani,
and the TMJ is seen laterally
48. Tensor tympani muscle is seen
along the medial wall of the middle
ear, with the cochleariform process
separating it from the eustachian
tube below.
The anteriormost part of the
cochlea is medial to the tensor
tympani.
The geniculate ganglion is seen
as a small lucency superior to the
cochlea
Geniculate ganglion level
49. Superior and inferior walls of the EAC are
seen well.
The TM may be identified as a thin
filamentous structure extending from the
scutum superiorly and coursing parallel to the
plane of the long process of the malleus to
attach to the limbus inferiorly.
The head and neck of the malleus can be
seen in the epitympanic space, with the tendon
of the tensor tympani muscle attaching to
neck.
The basal and second turn of the cochlea are
visualized.
The labyrinthine and tympanic segments of
the facial nerve are seen as two lucencies
superior to the cochlea.
Anterior tympanic level
50. This level shows the long process and lenticular process of the incus
and the incudostapedial articulation as an L-shaped configuration.
Prussak’s space is seen between the incus and
scutum.
The tympanic segment of the facial nerve canal is seen along the
medial wall of the middle ear just superior and lateral to the cochlea.
Midtympanic level
Prussak’s space
51. The full extent of the IAC is well
visualized at this level, with the
central crista falciformis dividing
the canal into two portions.
Oval window is seen as a bony
defect in the lateral portion of the
vestibule.
Beneath the lateral SCC, the
horizontal portion of the facial
nerve canal appears as a small
circular structure.
The epitympanic space lies just
lateral to the lateral SCC.
Oval window level
52. Posterior tympanic level
The facial nerve recess is lateral
to and the sinus tympani medial to
the pyramidal eminence.
The round window niche is seen
along the basal turn of the cochlea.
53. The jugular foramen – dome
shaped outline.
The mastoid segment of the
facial nerve canal can be identified
lateral to the jugular foramen,
running nearly vertical and
extending toward the stylomastoid
foramen.
The mastoid antrum is seen
superiorly and laterally.
Portions of the lateral and
superior SCCs can be seen.
Jugular foramen level
55. Stenvers’ view
Stenvers’ view MIDSUPERIOR SCC
LEVEL. The superior SCC is seen in cross
section.
Stenvers’ view COMMON CRUS LEVEL. In
addition to common crus, portions of the
posterior SCC and superior SCC are seen.
Oblique coronal projection.
Superior anatomic detail.
Used to assess electrode placement following the insertion of
a cochlear implant.
56. Stenvers’ view COCHLEA LEVEL. The
turns of the cochlea are seen, as is the
round window and descending facial
nerve canal .
Stenvers’ view INCUDOMALLEOLAR
JOINT LEVEL. The incudomalleolar
joint is well seen between body of
incus (I) and head of malleus (M).
57. Pöschl’s view
The plane of projection is perpendicular to the long
axis of the temporal bone.
Projection the temporal bone is imaged from its
anteromedial to posterolateral aspects.
The superior SCC is seen as a ring, and
the posterior SCC is seen in cross section.
The tympanic segment of the facial nerve
canal is seen in cross section.
PÖSCHL’S VIEW
MIDSUPERIOR
SCC LEVEL
The modiolus (m) is seen along its
axis
PÖSCHL’S VIEW MODIOLUS LEVEL
59. COCHLEAR ANOMALIES (CLASSIFICATION)
Have different presentation depending on the timing of
developmental arrest.
Divides congenital cochlear anomalies according to the timing of
the developmental arrest.
Complete labyrinthine aplasia or Michel deformity: 3rd week
Cochlear aplasia : 4th week
Common cavity malformation to the cochlea and vestibule: early
5th week
Cochlear incomplete partition type including Cystic
cochleovestibular anomaly: late 5th week
Cochlear hypoplasia: 6th week
Cochlear incomplete partition type II including mondini
dysplasia: 7th week
60. Complete labyrinthine aplasia
Congenital abnormality of the inner ear and is
characterised by bilateral absence of differentiated inner ear
structures with resultant anacusis.
MICHEL APLASIA,
62. Abnormal cochlea
Only 1.5 turns (instead of the
normal 2.5 turns)
Normal basal turn with a cystic
apex in place of the distal 1.5
turns
Enlarged vestibule with
normal semicircular canals
Enlarged vestibular aqueduct
containing a dilated endolymphatic
sac
MONDINI MALFORMATION
incomplete partition type II anomaly with large vestibular
aqueduct.
