Imaging of the temporal bone

IMAGING OF THE TEMPORAL BONE

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 – T umor, vascular lesion, abscess formation, sigmoid sinus thrombosis, intracranial spread of disease.

11. Axial and Coronal section

12. Coronal Coronal Axial Axial

13. 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

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

15. 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

16. Axial CT

17. Axial CT

18. Coronal CT

19. Coronal CT

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

21. Sclerosed Mastoid

22. Anteriorly positioned sigmoid sinus

23. Anatomical variation Koerner septum Deep sinus tympani Dehiscent Tegmen

24. High riding Jugular Bulb

25. Low Tegmen

26. Aberrant Carotid Artery

27. 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.

28. 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

29. Chronic Otitis Media Chronic Otomastoiditis

30. Coalescent Mastoiditis

31. Cholesteatoma

32. Limited Cholesteatoma

33. Cholesteatoma involving Proximal Tympanic segment of Facial nerve

34. Dehiscent Facial Nerve Canal

35. Congenital Cholesteatoma

36. Post -Surgical case Pre-op Post-op

37. Postsurgical Cholesteatoma

38. Labyrinthine Fistula

39. Uneven Mastoid Cavity

40. Bony overhang Bony Overhang

41. Destructed post meatal wall A B A B C

42. Grade V Retraction Pre-op Post-op

43. Erosion of Ossicle

44. OME in Imaging

45. Chronic Otitis Media(COM)

46. Tympanosclerosis

47. 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

48. Fibroepithelial Polyp

49. Foreign body in EAC

50. Tympanic Paraganglioma

51. JuguloTympanic Paraganglioma

52. Facial Nerve Haemangioma

53. Temporal Bone Malignancy

54. Facial Nerve Schwannoma

55. Malignant Otitis Externa

56. Temporal Bone Fracture

57. Imaging in Otosclerosis

58. Otosclerosis involving Cochlea

59. CT Scan at Round Window level

60. Area of Posterior Tympanotomy

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

62. Incomplete Partition Type 2 Mondini deformity

63. Labyrinthine aplasia(Michel deformity)

64. T2 MRI

65. T2 MRI

66. Axial and Coronal MRI

67. A B D D C E

68. MRI Sagittal section

69. 3D reconstruction of MRI

70. Unilateral SNHL due to Cochlear nerve Aplasia/Hypoplasia

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

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

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

74. Cochlear Hypoplasia

75. Cochleovestibular aplasia -Michel Deformity

76. Ossification of Cochlea

77. Common cavity

78. Common Cavity S mall common cavity with the narrow lAC

79. Labyrinthine Ossificans

80. Cochlear Nerve Aplasia

81. Cochlear nerve aplasia

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

83. Poschl reformat

84. Superior Semicircular Canal Dehiscence(SSCD)

85. Enl arged Endolymphatic Duct and Sac

86. Sensorineural Hearing Loss

87. I ntracanalicular T umor in the left IAC

88. 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

89. Courtesy: Dr Sampath

90. Granulation tissue in CT and MRI

91. CT and MRI in Cholesteatoma

92. Cholesterol granuloma in CT and MRI

93. Cholesterol granuloma in CT and MRI

94. Mucolele in MRI

95. Metastasis in Petrous Bone - CT and MRI

96. V estibular schwannoma

97. Vestibular Schwannoma and coexistent Aachnoid Cyst

98. 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

99. THANK YOU Otology Dr Kanu BMMU Bangladesh www.drkanuotology.com [email protected]