This document provides an overview of temporal bone anatomy and imaging techniques for evaluating the temporal bone. It describes the major components of the temporal bone including the external auditory canal, middle ear, inner ear, internal auditory canal, and surrounding bones. Imaging tools like CT and MRI are discussed along with techniques for each. Examples of normal anatomy, anatomical variations, and various pathological conditions are shown through CT and MRI images with explanations. The importance of understanding temporal bone imaging for otologists and radiologists is emphasized to accurately diagnose and treat temporal bone diseases.

1. Kanu Lal Saha
Associate Professor
Otology Division
Department of Otolaryngology & Head-Neck Surgery
Bangabandhu Sheikh Mujib Medical University
Dhaka, Bangladesh.
Imaging of the Temporal Bone
The eyes do not see when brain does not know

2.  Squamous: Forms lateral wall of middle cranial fossa
 Mastoid: Areated posterolateral part
 Petrous: Pyramiadal shape medial part containing inner ear, internal
auditory canal and petrous apex.
 Tympanic: U-shaped bone forming bony EAC.
 Styloid: Forms styloid process after birth.
TEMPORAL BONE

3. Major components of Temporal bone
External auditory canal(EAC)
Middle ear-mastoid(ME-M)
Inner Ear(IE)
Petrous apex(PA)
Internal auditory canal
Facial nerve
Petrous internal carotid
artery(ICA)

4. Imaging Anatomy-Middle Ear-Mastoid
Epitympanum(attic): Middle ear above the line from scutal tip to
tympanic CN7
Tegmen tympani: Roof of middle ear cavity
Prussak space: Lateral epitympanic recess
Mesotympanum: Middle ear proper
Posterior wall: 3 key structures
Facial recess, pyramiadal eminence, sinus tympani
Medial wall: Lateral semicircular canal, tympanic segment
CN7,oval window and round window
Hypotympanum: shallow trough in floor of middle ear
Mastoid sinus: 3 Key structures
Aditus ad antrum: Connects epitympanum to mastoid antrum
Mastoid antrum: large cetral mastoid air cell
Koerner septum: Part of petrosquamosal suture running
posterolaterally through mastoid air cells.

5. Imaging Anatomy(Inner Ear)
Bony labyrinth: Bone confining cochlea, vestibule and
semicircular canals
Perilymphatic spaces
Perilymph
Membranous labyrinth
Vestibule: (utricle and sacule),semicircular ducts,scala
media of cochlea,endolymphatic duct and sac
Endolymph
Cochlea: 2 ½ turn,modiolus,3 spiral chambers(scala
tympani,scala vestibule and scala media)
Semicircular canals:
SSCC: projects cphalad;bony ridge over SSCC in in roof of
petrous pyramid
LSCC: Projects into middle ear with tympanic CN7 on under side
PSCC: Projects posteriorly parallel to petrous ridge

6. Imaging Anatomy

7. Imaging Anatomy

8. Imaging Anatomy

9. Imaging Tools
• CT Scan
Conventional CT Scan- High resolution multidetector CT
Cone beam CT
-it employs cone-shaped beam of X-rays
- A single rotation of gantry is sufficient
- Low radiation dose though high spatial resolution.
- Acquisition time is long
- Prone to motion artifacts
• MRI
Conventional(T1,T2)
Diffusion weighted Imaging(DWI-EPI and Non-EPI)

10. Imaging technique CT Scan
• Fine section - .5 mm to 1 mm thickness.
• Axial scan –
Top of petrous apex to inferior tip of mastoid parallel to infraorbitomeatal line
• Coronal scan-
Coronal images are reconstructed from axial images
• Three-dimensional (3D)Image
Depict complex anatomy
• High spatial resolution bone algorithm
• Non-contrast scan in most instances
• Contrast scan in some conditions –
Tumor, vascular lesion, abscess formation, sigmoid sinus thrombosis,
intracranial spread of disease.

12. Axial and Coronal section

14. Coronal Coronal
Axial Axial

15. How to read CT Temporal Bone
Patient Data (Name & ID No.)
Date of CT Scan
Type of CT Scan
Size of Cuts ( + Contrast)
Bone window verses soft tissue

16. Evaluation of CT Temporal Bone
Normal anatomy
Normal variants (comparing both side)
 Pathology

17. Things to look for CT Scan
Degree and pneumatization of temporal bone
air cell
Position of tegmen,sinus plate,jugular bulb,
carotid canal ,facial nerve
Cochlear nerve and labyrinthine patency
Disease extensions
Evidence of previous surgery

18. Axial CT

19. Axial CT

20. Coronal CT

21. Coronal CT

22. Pneumatization of Mastoid air cell
Sclerotic mastoid Diploic mastoid Pneumatized mastoid

23. Sclerosed Mastoid

24. Anteriorly positioned sigmoid sinus

25. Anatomical variation
Koerner septum Deep sinus tympani Dehiscent Tegmen

26. High riding Jugular Bulb

27. Low Tegmen

28. Aberrant Carotid Artery

29. CT findings in Pathological condition
 Involvement of bony outline of EAC, middle ear and
mastoid, ossicular chain, inner ear, and facial nerve canal
 Identification of masses or opacification within temporal bone
area
Difficult to differentiate between different type of
opacity such as fluid or cholesteatoma,cholesterol
granuloma,granulation tissue or malignancy.

30. Imaging strategy/indications
 Chronic Otitis Media/Chronic Oto-mastoiditis
 Cochlear Implantation
 Congenital Aural dysplasia(CAD), External Auditory Canal lesions
 Aural mass
 Facial nerve disorder
 Temporal Bone trauma
 Otitis externa
 Hearing Loss
 Tinnitus
 Vertigo and Dizziness

31. Chronic Otitis Media
Chronic Otomastoiditis

32. Coalescent Mastoiditis

33. Cholesteatoma

34. Limited Cholesteatoma

35. Cholesteatoma involving Proximal
Tympanic segment of Facial nerve

36. Dehiscent Facial Nerve Canal

37. Congenital Cholesteatoma

38. Post -Surgical case
Pre-op
Post-op

39. Postsurgical Cholesteatoma

40. Labyrinthine Fistula

41. Uneven Mastoid Cavity

42. Bony overhang
Bony Overhang

43. Destructed post meatal wall
A B
A B
C

44. Grade V Retraction
Pre-op
Post-op

45. Erosion of Ossicle

46. OME in Imaging

47. Chronic Otitis Media(COM)

48. Tympanosclerosis

49. Aural mass
 Retrotympanic mass
 An auricular mass in EAC
Retrotympanic lesion on otoscopy
CT and MRI are complementary.
Contrast-enhanced MRI –
if the CT findings raise concern for a neoplasm

50. Fibroepithelial Polyp

51. Foreign body in EAC

52. Tympanic Paraganglioma

53. JuguloTympanic Paraganglioma

54. Facial Nerve Haemangioma

55. Temporal Bone Malignancy

56. Facial Nerve Schwannoma

57. Malignant Otitis Externa

58. Temporal Bone Fracture

59. Imaging in Otosclerosis

60. Otosclerosis involving Cochlea

61. CT Scan at Round Window level

62. Area of Posterior Tympanotomy

63. Narrow Facial Recess
Normal facial recess Narrow facial recess
Ref. Sennaroglu

64. Incomplete Partition Type 2
Mondini deformity

65. Labyrinthine aplasia(Michel deformity)

66. T2 MRI

67. T2 MRI

68. Axial and Coronal MRI

69. A B
D DC
E

70. MRI Sagittal section

71. 3D reconstruction of MRI

72. Unilateral SNHL due to Cochlear nerve Aplasia/Hypoplasia

73. Axial and coronal CT(Aplasia/Hypoplasia of CN)

74. Axial and Coronal MRI(Aplasia/Hypoplasia of CN)

75. Sagittal Oblique Imaging through IAC
(Aplasia/Hypoplasia of CN)

76. Cochlear Hypoplasia

77. Cochleovestibular aplasia -Michel Deformity

78. Ossification of Cochlea

79. Common cavity

80. Common Cavity
Small common cavity with the narrow lAC

81. Labyrinthine Ossificans

82. Cochlear Nerve Aplasia

83. Cochlear nerve aplasia

84. Congenital Aural dysplasia(CAD),
External Auditory Canal lesions

85. Poschl reformat

86. Superior Semicircular Canal Dehiscence(SSCD)

87. Enlarged Endolymphatic Duct and Sac

88. Sensorineural Hearing Loss

89. Intracanalicular Tumor in the left IAC

90. Granulation Tissue / Cholesterol
Granuloma/Cholesteatoma/Effusion
 Appears at CT as nonspecific, nondependent radiopacity
 Granulation tissue enhances intensely with gadolinium on T1-weighted MR images
Cholesteatoma no enhancement with gadolinium on T1-weighted MR images
Cholesterol granuloma has bright signal on all pulse sequences

91. Courtesy: Dr Sampath

92. Granulation tissue in CT and MRI

93. CT and MRI in Cholesteatoma

94. Cholesterol granuloma in CT and MRI

95. Cholesterol granuloma in CT and MRI

96. Mucolele in MRI

97. Metastasis in Petrous Bone - CT and MRI

98. Vestibular schwannoma

99. Vestibular Schwannoma and coexistent Aachnoid Cyst

100. Conclusion
Inappropriate report misleads the surgeon
Poor image involves wastage of money and radiation hazard
Otologist must know the basics of temporal bone imaging
Radiologist should be aware of expected and useful reporting
Radiologist and Otologist should be always in compliance to get
the real benefit of this excellent tool

101. THANK YOU
Otology Dr Kanu BMMU Bangladesh
www.drkanuotology.com
drklsaha@gmail.com