This document describes various imaging modalities and techniques used to examine the petrous bone and inner ear anatomy. It outlines CT and MRI sequences that can be used and discusses what structures like the external auditory canal, middle ear, semicircular canals and cochlea appear as on different scans. It also provides examples of pathologies that can be imaged in the temporal bone like cholesteatoma, otitis media, fractures and tumors.

1. Imaging modalities of the petrous bone.
Dr/ ABD ALLAH NAZEER. MD.

2. Diagram for the external, middle and inner ear.

3. CT techniques for petrous examination

9. 1. External auditory canal.
2. Tympanic membrane.
3. Ossicles (3: malleus, 3': incus, 3'': stapes).
4. Prussack space.
5. Scutum.
6. Tympanic tegmen.
7. Tympanic sinus.
8. Facial nerve fossa.
9. Facial nerve.
10. Antrum of mastoid.
11. Oval window.
12. Vestibule.
13. Semicircular canals (13: anterior, 13': lateral, 13'': posterior).
14.Cochlea.
15.Internal auditory canal.
16. Vestibular aqueduct.

10. Axial images.

11. Coronal
images.
Coronal
images.

29. Sinus tympani
Facial recess.
Eustachian tube

30. Inner ear.

36. One and half and basal turn of the cochlea.

45. Necrotizing otitis externa (NOE), also known as malignant otitis externa, is a severe
invasive infection of the external auditory canal (EAC) which can spread rapidly to
involve the surrounding soft tissue, adjacent neck spaces and skull base.

46. (A-C) Malignant otitis externa: coronal contrast-enhanced CT scan (A) shows
soft tissue thickening of the EAC (arrow). Axial HRCT image (B) shows
irregularity of the right TM joint (arrowhead) and mastoid (arrowhead). Axial
contrast-enhanced CT scan (C) shows a temporalis abscess (arrow).

47. Malignant Otitis Externa

49. External auditory canal exostoses.

50. (A-C) Cholesteatoma of the EAC: non-contrast coronal CT
scan (A) and axial HRCT image (B) show a hypodense lesion
in the right EAC (arrow in A and arrowhead in B) invading
the mastoid (stage III). 3D volume rendered image (C)
shows a small, post-biopsy defect in the mastoid wall.

51. Squamous cell carcinoma of the external auditory canal.

52. The middle ear is an-air filled chamber in the petrous
part of the temporal bone that is split into two parts: the
tympanic cavity proper and the epitympanic recess or
attic. It contains the three auditory ossicles whose
purpose is to transmit sound vibrations from the tympanic
membrane to the medial wall of the inner ear.
Related pathology:
Chronic otitis media.
Cholesteatoma.
Otosclerosis.
Trauma.
Vascular anomalies.
Aberrant carotid artery.
Dehiscent jugular bulb.

55. Chronic otitis media.

58. Congenital
cholesteatoma.

60. Congenital cholesteatoma.

70. Diffusion weighted imaging (A) and apparent diffusion coefficient map (B) reveal
restricted diffusion by a lesion situated in the right external auditory canal (arrow)

71. A and B, CT shows soft tissue (arrow) in the mastoid defect, external auditory canal, and epitympanum with
bony erosion of the lateral semicircular canal. C and D, MR images show the extent of cholesteatoma and
demonstrate a large area of hyperintensity on HASTE DWI in the mastoid defect and middle ear with T2
hypointensity (arrow, C), and mild T1 hyperintensity but no definite enhancement (arrow, D). A portion of the
right lateral semicircular canal is obscured by the soft-tissue mass (C), again consistent with the fistula on CT.

72. DWI sequences obtained in a patient with postoperative changes.
Increased diffusion signal intensity is seen in the right middle ear and
mastoid defect (arrow), with cholesteatoma confirmed at surgery.

74. Bilateral cholesteatoma with typical restricted diffusion.

75. (A-D) Cholesteatoma of the EAC: coronal T1W MRI image (A) shows a hypointense lesion
(arrow) in the right temporal bone. Axial STIR MRI image (B) shows a hyperintense lesion
(arrow) extending into the mastoid. Diffusion-weighted (C) and axial apparent diffusion
coefficient (ADC) (D) images show restricted diffusion (arrows).

76. Cholesterol granuloma.

77. Cholesterol granuloma. CT (A) demonstrates an expansive mass
involving the PA; there is no evidence of bony erosion. Typically T1
WI (B) and T2 WI (D;E) show an hyperintense lesion with mass
effect on the right prepontine cistern. No CE is seen (C).

78. Petrous apex meningocele/ Arachnoid cyst.

79. Mucocele.

80. Petrous apicitis.

81. Langerhans cell histiocytosis.

85. Aberrant course of the ICA in a 25-year-old man
presenting with pulsatile tinnitus. A, Enhanced
axial CT image demonstrates an abnormal
lateral course of the right ICA through the middle
ear (white arrow). Also note dehiscence of the
overlying bony plate. B, Anteroposterior
projection image from the MR angiogram of the
same patient demonstrates decreased caliber
and lateral deviation of the aberrant ICA on the
“right reversed-7 sign” (black arrow).

87. Temporal bone fractures are usually a sequela
of blunt head injury, generally from severe
trauma. Early identification of temporal bone
trauma is essential to managing the injury and
avoiding complications.
Classification: direction
Temporal bone fractures classically are
described concerning the long axis of
the petrous temporal bone, being classified as:
Longitudinal fractures.
Transverse fractures.
Mixed fractures.

91. Right and left axial petrous temporal bone CT.

94. Bilateral vestibular aqueduct syndrome.

101. Right ear shows bony
defect displayed by
oblique reformation
(double window
view) (a). Coronal
plane also shows the
defect in (b). The left
ear shows similar
findings in (c and d).

102. Superior semicircular dehiscence.

104. Axial (a) and coronal (b) HRCT images of the right temporal
bone in an adult patient with right-sided CHL. A hypodense
demineralised plaque (arrow) is noted in the region of the
fissula ante fenestram in keeping with fenestral otosclerosis

114. Labyrinthine ossification.

115. Bilateral calcification of the basal turn of cochlea,
related to labyrinthine ossificans.

117. VIII cn schwannoma.

118. Endolymphatic sac tumor. Lesion shows high signal on T2 WI (A), within hyperintense foci on T1-wi B),
typically located in the posterior petrous ridge. Post gadolinium T1 WI (C) reveals heterogeneous CE.
Notice the involvement of the internal auditory canal. Axial CT and 3D VR reconstruction (D, E) show
typical permeative bone changes of ELST; notice the involvement of internal auditory canal.

119. Metastasis. Ax T2 WI (A) reveals area of inhomogeneous high signal
filling the right PA, post gadolinium Ax/CorT1 WI (B;C) show diffuse CE.
Notice adjacent enhancing fat of the clivus and of VIII C.N (arrow in C).