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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
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.
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
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.
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
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
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