this prsentation incluses HRCT temportal bone cross sectional anatomy images axial saggital and coronal with labelled diagram. This presentation help alot for radiology resident. Thanks.

1. HRCT TEMPORAL BONE
Dr. Pradeep Kumar
MD Radiodiagnosis

4. Radiographic positions of mastoids
The mastoid process is a part of the temporal bone which is also comprised of tympanic,
petrous and squamous parts. Accordingly, examination of the mastoid can be possible
using the following projections:
Law view: The X-ray beam is directed at a 15 degree oblique plain cephalocaudally while
the skull's sagittal plane is parallel to the X-ray film.
Law view: The X-ray beam is directed at a 15 degree oblique plain
cephalocaudally while the skull's sagittal plane is parallel to the X-ray film.

5. Stenver's view: It is also called an Axio-anterior oblique posterior view. The X-ray
beam is directed at a 14 degree angle caudally and the head faces the film with
slight flexion and rotation at an angle of 45 degrees to the oppositeside.

6. Transorbital view: (posterioanterior and anteroposterior): The X-ray
beam is directed either postero anteriorly or anteroposteriorly along
the orbito-meatal line at a 90 degree angle to the film.

7. Town's view: It is an anteroposterior view with a 30 degree fronto-occipital axial tilt.
It helps in visualization of the temporal bones of, arcuate eminence, mastoid antrum,
superior semicircular canal, internal auditory meatus, cochlea and external auditory
meatus. It is also valuable in the diagnosis of apical petrositis and acoustic neuroma.

8. Axial anatomy from inferior to superior
At the most inferior level we see the facial nerve passing inferiorly to finally reach
the stylomastoid foramen (not shown in this image).
The carotid artery is shown within the carotid canal. Also at this
level is the top of the jugular bulb.
Coronal anatomy
The petrous bone is positioned in an oblique orientation from posterolateral
to anteromedial.
As a result most structures will be sectioned obliquely on coronal images.
The following coronal images go from anterior to posterior.
First we will see the tympanic membrane with the ossicles, followed
by the cochlea, antrum and semicircular canals.
Finally the most posterior image will show the point where the facial nerve exits the
temporal bone at the stylomastoid foramen.

9. Glenoid fossa
Scissura eardrum
Fascial canal
Mastoid air cells.
Occipital condyle
Jugular foramen.
Foramen magnum
Carotid foramen.
Tensor tympani

10. Fascial canal Jugular foramen.
Tensor tympani
Eustachian tube
Corda tympani canal

11. Fascial canal
Jugular foramen.
Tensor tympani

12. Tensor tympani
Jugular foramen.
Tympanic membrane
Corda tympanicanal
Fascial canal

13. Tendon for Tensor tympani
Jugular foramen.Osseous fascial canal
External auditory canal

14. Petrous Apex.
Osseous fascial canal
Inferior handle of malleus
Jugular
foramina.
Jugular Bulb.
Tendon for Tensor tympani

15. Tendon for Tensor tympani
Apical turn of the cochlea
Basal turn of the cochlea
Handle of malleus
Osseous fascial canal

16. Handle of malleus
Long process of Incus
Osseous fascial canal
3rd portion
Tendon for Tensor tympani
Cochlear process
Basal turn of cochlea
Aqueduct of cochlea
Promontory

17. Head of malleus
Wall for middle ear
Body of Incus
Osseous fascial
canal (3rd portion)
Tendon for Tensor tympani
Cochlear process
Round window
Pyramidal eminence

18. Pyramidal eminence
VestibuleOsseous fascial
canal (3rd portion)

19. Ovale Window
Osseous fascial
canal (2nd portion)

20. Osseous fascial
canal (1st portion)
Mastoid antrum
Extreme upper
jugular foramen.

21. Internal acoustic meatus
Aditus ad antrum
Mastoid antrum

22. Lateral semicircular
canal
Aditus ad antrum

23. Mastoid antrum

24. Mastoid antrum
Mastoid foramen
Upper jugular
foramen.
Vestibular aqueduct

25. Mastoid foramens

26. Mastoid
canal
Superior semicircular canal.
Posterior semicircular canal.
jugular foramen.

27. Mastoid antrum
Ear pinna
Foramina for internal jugular vein
Coronal section

28. internal jugular
vein foramen
Mastoid antrum

29. Mastoid antrum
Ear pinna
internal jugular
vein foramen

30. Posterior
semicircular canal.
internal jugular
vein foramen

31. Aditus ad antrum
Bony canal for
Corda tympanum
3rd portion of osseous fascialcanal.
internal jugular
vein foramen
Pyramidal eminence

32. Lateral semicircular canal.
3rd portion of osseous fascialcanal.
Ear pinna
internal jugular
vein foramen
Pyramidal eminence
Jugular -facial
foramen

33. Lateral semicircular
canal.
Superior semicircular
canal.
Pyramidal eminence
internal jugular
vein foramen
3rd portion of osseous fascialcanal.

34. Lateral semicircular
canal.
Superior semicircular
canal.
internal jugular
vein foramen

35. internal jugular
vein foramen
Superior semicircular
canal.
Cochlear aqueduct
Round window.
Septum
epitympanum
jugulare

36. epitympanum
Round window.
Tegmen tympani.
Lateral semicircular
canal.

37. Lateral semicircular
canal.
2nd portion of
osseous fascial canal.
Ovale window.
Ear drum
Vestibule
Malleous
Epitympanum

38. Epitympanum
Tegmen tympani
Incus
Drum spur
External auditory
meatus
Tympanic membrane
Superior semicircular
canal.
Internal acoustic meatus
Promontory

39. Epitympanum
Tegmen tympani
Drum spur
Handle of malleous
Tympanic membrane
Petrous apex.
1st portion of
osseous fascial canal
Basal turn of cochlea

40. Tympanic
membrane
Drum spur
Tegmen tympani
malleous
1st portion of
osseous fascial canal
Internal acoustic meatus

41. 1st portion of
osseous fascial canal
Cochlea
2nd portion of
osseous fascial canal
Malleous
Head
Neck
Handle
Tendon for Tensor tympani Septum epitympanum jugulare

42. Cochlea
Carotid
canal
Cochlear
process

43. Geniculate
ganglia.
Myotendinous junction
of tensor tympani
Carotid
canal
Apex of
Cochlea
Petrous apex

44. Geniculate
ganglia.
Muscle belly of
tensor tympani
Aditus antrum
Petrous
apex
Carotid
canal

45. Muscle belly of
tensor tympani
Petrous
apex
Carotid
canal
Aditus antrum

46. Head of malleous
Body of incus

47. Spiral laminar bone
with cochlear apex
Cochlea
(basal turn)

48. Pyramidal eminence
Promontory
Sinus tympani.
3rd portion ofosseous
fascial canal
Cavernous
Tympanicum

49. The internal auditory canal:
-Has three parts: the internal acoustic meatus (medial opening), the
canal (an average of 8 mm) and the fundus, of irregular shape
(modulates the passage of the VII and VIII cranial nerves).
-Nervous contents: the facial nerve (the largest in size) and the
cochleo-vestibular nerve that divides into the cochlear nerve and the
vestibular nerve which further divides itself into the superior
(innervates the utricle and the ampulla of the superior and lateral
SCC), and the inferior branches (innervates the saccule and the
ampulla of the posterior SCC).
The singular nerve (or the posterior ampullary nerve) has its proper
canal, the singular canal, in the postero-inferior quadrant of the
fundus that can be often be observed with 3T imaging.
-Vascular content: arterial by the labyrinthine artery and venous
with three drainage pathways (internal auditory vein, vein of
cochlear aqueduct and vein of vestibular aqueduct).
The inner ear MR anatomy.

53. Axial section through the inner auditory canal (IAC) and the
labyrinthe with visualization of the cochlear and inferior vestibular
nerves. The utricular macula is also well depicted.

54. Anterior coronal section through the IAC. Outline of the facial nerve in
its complete cisternal course, the cochlear nerve is only partially viewed.

55. Posterior coronal section through the IAC. Vestibular nerve
division and vestibular ganglion (of Scarpa) are visualized.

56. Appearance variant of the vestibular nerve with inferior vestibular division into
the saccular nerve (that innerves the saccule) and the posterior ampullary nerve (for
the ampulla of the posterior semicircular canal). The singular canal is also frequently
observed, not shown in this figure. Coronal and sagittal sections through the IAC.

57. Sagittal seriate sections of the IAC from medial (left), showing the
pontocerebellar cistern, to lateral (right), showing the fundus and inner ear structures.

58. Cochlear nerve at the fundus of the IAC and its passage via the modiolus
to the cochlea in an oblique sagittal section. This finding is of clinical
importance when studying the inner ear malformations.

59. Heavily T2 coronal section respective to the IAC. Vestibular and cochlear
structures are seen, note the utricular macula and spiral lamina.

60. Sagittal section respective to the IAC through the inner ear in a 3D
Heavily T2 sequence. This section is also orthogonal to the macula of
the utricle and unfolds partially the cochlea.

61. Oblique coronal section through the anterior labyrinth
and fundus of the IAC, 3D Heavily T2 sequence.

62. FLAIR sequence in the axial plane four hours after Gd intravenous
injection, the saccule and part of the utricle are visualized.

63. Axial FLAIR Gd sequence through the utricle, the saccule is partially visualized.

64. Heavily T2 in the plane of the lateral semicircular canal (oblique
axial). The ampulla and its ampullary crest (low signal) are seen.

65. FLAIR Gd sequence section in the lateral SCC plane, passing through the utricle.

66. Section in the plane of the superior semicircular canal (plane of
Pöschl, sagittal to the petrous bone), with heavily T2 sequence.

67. Section in the same plane of the superior semicircular canal with FLAIR Gdsequence.

68. T2 sequence in the plane of the posterior SCC (plane of Stenver,
coronal to the petrous bone). Notice the common part of the
superior and posterior semicircular canals, i.e. the common crus.

69. FLAIR and Heavily T2 sequences, sections in the coronal plane. Notice the
position of the utricular macula (T2 sequence) relative to the utricle (FLAIR).

70. HRCT Temporal bone anatomy
on the basis of level

71. Planes of scanning
 Axial
 30 Degrees to anthropological base line
 Parallel to lateral SCC.
 Best displays inner & middle ear.
 Sections parallel to the hard Palate
 Direct Coronal plane
 patient head extended in prone or supine with 105 degree
 plane is perpendicular to the lateral SCC
 Sections are parallel to posterior wall of maxillary sinus
 Saggital plane
2
105
0
30

72. Temporal Bone
3
1.Squamous
Lateral wall of MCF
2.Petrous
Encloses Labyrinth
3.Mastoid
Mastoid air cells
4.Tympanic
Forms bony EAC
5. Styloid
Forms Styloid process

74. • EXTERNAL EAR
• MIDDLE EAR
• INTERNAL EAR
5
EAC
Bony & membranous labyrinth

75. 6
EXTERNAL EAR
Cartilaginous
Lateral 1/3rd
Osseous
Medial 2/3rd
Tympanic membrane-makes 55 degree angle
With floor of the meatus

76. 7
Boundaries & Communications Of Middle Ear

77. 8
1)PROMOTARY- Round bulge produced by basal turn of cochlea
2)FENESTRA OVALIS -Lies postero- superior to promontory & connects
middle ear with vestibule and is occupied by footplate of stapes
3)FENESTRA ROTUNDA- Posteroinferiorly to oval window & connects ME
with scala tympani of cochlea.
4)PROMINENCE OF FACIAL NERVE CANAL -Runs backwards just above the
oval window to reach the lower margin of aditus.
Medial wall of middle ear:

78. 9
ANTERIOR WALL
1)Superior-opening of
canal for tensor tympani.
2) Middle –opening of
auditory tube.
3)Inferior-thin plate of
bone separating from
carotid canal.
POSTERIOR WALL
1) Aditus to mastoid
2) Fossa incudis-lodges the short process of incus.
3) Pyramidal eminence-attachment for stapedial tendon.

79. • The scutum is normally thin and sharply edged;
and is an important bony landmark as it is one of
the bony structures eroded early by a
cholesteatoma.
•
• Scutum, the tympanic membrane and the tympanic
annulus are best demonstrated on coronal images
at the mid bony portion of the external auditory
canal.

81. • Cochlea
• The perilymphatic space of
vestibule is continuous with
the cochlea anteriorly.
• The cochlea is a conical
structure,extends for 2.5-
2.75turns
• Promontory
(P) is the projection raised by
the basal turn of cochlea.
• The basal turn opens into the
round window niche
Coronal
Middle
turn
Axial

82. • The vestibule
consists of the
superior utricle and
the inferior saccule.
• The semicircular
ducts open into the
utricle.

83. • The cochlear aqueduct
contains the
perilymphatic duct
while the vestibular
aqueduct contains the
endolymphatic duct
and the intraosseous
portion of the
endolymphatic sac.

85. Facial Nerve
• VII n:-
– Intracranial segment
– Labyrinthine segment
– Tympanic segment
– Mastoid portion
– Parotid segment
41

86. • The facial nerve, from the lateral end of the
internal auditory canal enters the petrous bone as
the labyrinthine portion running anterolaterally,
superior to the cochlea and towards the anterior
genu (geniculate ganglion).
• Then it makes an abrupt turn to run
posterolaterally along the medial attic wall
beneath the lateral semicircular canal as the
tympanic portion towards the posterior genu.
• And finally turns inferiorly as the descending
(mastoid) portion to exit at the stylomastoid
foramen.

87. How to identify Facial nerve canal?
• Axial: at level of
Epitympanum, it is seen as a
linear structure medial to
ice-cream cone.
ronal: At level of OW,it is
seen as a round structure
with bony outline between
OW inferiorly and Lateral
Semicircular canal
(LSC)superiorly.
•CoronaCl: oA

88. 46
Axial sections-caudal to cephalad
1.Axial hypotympanic-jugular foramen level
1)carotid canal & jugular
Fossa forming snowman
Configuration
2)opening of auditary
Tube
3)petrooccipital fissure
4)TM joint and mandibular
Condyle

89. 47
Jugular fossa
Temporo
mandibular jt
Auditory tube
Carotid canal
Petro
occipital fissure

90. 48
2.Axial inferior tympanic
level
1)ant &post walls of EAC
2)descending facial nerve canal
3)carotid canal
4)cochlear aqueduct
5)long process of
Malleus.

91. 49
EAC
Descending
facial nerve
Cochlear
aqueduct
Promontory
canal For tensor
tympani

92. 50
3.Axial mid tympanic level
1)neck of malleus ,long process of
incus and stapes
2)semicanal for tensor
tympani
3) 3 turns of cochlea
4)facial nerve canal

93. 51
malleus
incus
stapes
Round window

94. 52
Oval window
IAC
Scala tympani
Facial recess

95. 4. Axial Epitympanic
IAC level
• Ice-cream cone appearance-head of
malleus and body of incus
• Stapes –occasionally seen articulating
with oval window.
• Internal auditory canal
• Descending facial nerve canal
53

96. 54
Ice cream cone
appearance
Facial nerve
canal
Internal auditory
canal

97. • 1)mastoid antrum and its aditus
& Koerner’s septum
• 2) lateral semicircular canal and
vestibule
• 3) post semicircular canal
&vestibular aqueduct
• 4) IAC
• 5) sq part of temporal bone.
• 6) geniculate ganglion
55

98. 56
IAC
PROXIMAL LIMB OF 7TH
N
VESTIBULE
LATERAL SC CANAL ADITUS TO MASTOID
ANTRM
VESTIBULAR AQUEDUCT

99. 57
CORONAL SECTIONS
1. Coronal anterior tympanic level
-Head of malleus
-Tegmen tympani
-Basal & 2nd turn of
Cochlea
-Geniculate ganglion
- scutum

100. 58
HEAD OF MALLEUS
GENICULATE GANGLIA
IAC
COCHLEA
SQ TEMP
ORAL
BONE
SCUTUM

101. 59
2.Coronal mid-tympanic level
-L shaped incudo-stapedial articulation
-Stapes
-Oval window
-Tegmen tympani

102. 60
IAC
Oval Window
Incus in aditus
Stapes
Tegmen tympani

103. 61
3.CORONAL- OVALWINDOWLEVEL
•IAC
•Oval window
•Stapes
•Lateral SCC

104. 62
Vestibule
IAC
Sup SCC
Antrum
Lateral SCC
Oval window
EAC
Middle ear

105. 63
5.Coronal jugular foramen
level
•Jugular foramen
•Descending facial
Nerve
•Mastoid antrum
•Occipital bone and atlas

106. 64
Descending facial nerve
Jugular fossa
Mastoid AirCells

107. Role of MRI
• Excellent in studying Inner ear
– Membranous labyrinth
– Vestibule
– Saccule & utricles
• Preoperative evaluation in pts for Cochlear implants
• Toevaluate CP angle tumors
• Toevaluate Neurovascular bundles
• Functional assessment – Nerve stimulation
• Virtual scopy
65