This document contains 52 figures showing images from CT scans and MRI of the petrous temporal bone and inner ear. The images depict normal anatomy, various congenital abnormalities, infections, tumors and fractures. Specifically, they show electrode placement in the cochlea for hearing implants, labyrinthine deformities, vascular anomalies like jugular bulb dehiscence, cholesteatoma erosion, glomus jugulare and other tumors, acoustic neuromas, meningiomas and malignant otitis externa. The images provide examples of how different pathologies and conditions appear on axial, coronal and sagittal views of the temporal bone using CT and MRI.

1. 52
THE PETROUS TEMPORAL BONE
DAVID SUTTON

2. DAVID SUTTON PICTURES
DR. Muhammad Bin Zulfiqar
PGR-FCPS III SIMS/SHL

3. • Fig. 52.1 Stenver's view of the petro mastoid
with an extended electrode array in the first
and second coils of the cochlea. v = vestibule;
s = superior semicircular canal; i = internal
auditory meatus.

4. • Fig. 52.2 Perorbital view showing an
electrode array in the basal cochlear coil.
There is extensive pneumatisation to the
petrous apex. v = vestibule; i = internal
auditory meatus.

5. • Fig. 52.3 The sections for a routine axial CT
examination of the temporal bone shown on
a sagittal scout view.

6. • Fig. 52.4 The four most important sections in the study of
the petrous temporal bone by CT: the cochlear and
vestibular cuts in both corona! And axial planes. (A) The
position of these cuts is shown on a cast of the labyrinth of
the inner ear viewed from the lateral aspect. (B) Axial
plane. (C) Corona! plane. The internal auditory meatus and
oval window are well shown in both planes.

7. • Fig. 52.4 The four most important sections in the
study of the petrous temporal bone by CT: the
cochlear and vestibular cuts in both corona! And axial
planes. (A) The position of these cuts is shown on a
cast of the labyrinth of the inner ear viewed from the
lateral aspect. (B) Axial plane. (C) Corona! plane. The
internal auditory meatus and oval window are well
shown in both planes.

8. • Fig. 52.4 The four most important sections in the
study of the petrous temporal bone by CT: the
cochlear and vestibular cuts in both corona! And axial
planes. (A) The position of these cuts is shown on a
cast of the labyrinth of the inner ear viewed from the
lateral aspect. (B) Axial plane. (C) Corona! plane. The
internal auditory meatus and oval window are well
shown in both planes.

9. • Fig. 52.5 Six labelled axial sections of the
petrous temporal bone. Note that the oval
window is shown in the same section as the
second part of the facial nerve and the bodies
of malleus and incus and above the section
showing the crura of the stapes.

10. • Fig. 52.5 Six labelled axial sections of the
petrous temporal bone. Note that the oval
window is shown in the same section as the
second part of the facial nerve and the bodies
of malleus and incus and above the section
showing the crura of the stapes.

11. • Fig. 52.5 Six labelled axial sections of the
petrous temporal bone. Note that the oval
window is shown in the same section as the
second part of the facial nerve and the bodies
of malleus and incus and above the section
showing the crura of the stapes.

12. • Fig. 52.6 Six labelled coronal sections.

13. • Fig. 52.6 Six labelled coronal sections.

14. • Fig. 52.6 Six labelled coronal sections.

15. • Fig. 52.7 An axial CT
section showing a large
vestibular aqueduct with
a line depicting the plane
of reformatting, enabling
a measurement to be
made in the midportion of
the descending limb
(labelled 1 and measuring
2.0 mm in diameter).

16. • Fig. 52.8 An axial MR section through the posterior
cranial fossa at the level of the IAMB. The arrow points
to the nerves in the IAM on this T1 -weighted protocol.
Note the high signal from fat in the petrous apex.

17. • Fig. 52.9 (A) A similar section
to that in Figure 52.8 but T2
weighted using a fast spin-
echo sequence, giving greatly
improved spatial resolution.
The open arrow points to the
basilar artery, the small
arrow to the spiral ganglion
of the cochlear nerve. (B)
Tiny presumed acoustic
neuroma on the superior
vestibular nerve (arrow) in
another patient.

18. • Fig. 52.10 (AM) Sagittal MR sections T2-weighted
showing a grossly dilated endolymphatic sac
(asterisk) in a typical case of Pendred's syndrome.
Note also the sac in place of the distal 1.5 coils of
the cochlea, i.e. a typical Mondini deformity
(arrow).

19. • Fig. 52.11 Axial T 1 -weighted image at the
level of the IAMB but after contrast
enhancement. The arrow points to the second
part of the facial nerve.

20. • Fig. 52.12 (A) Coronal CT section showing high jugular fossa on
one side with diverticulum. The arrow points to the thin bone
separating the jugular bulb from the hypotympanum of the middle
ear. (B) MRA shows the large jugular bulb (arrow).

21. • Fig. 52.13 Line drawings based on axial CT
sections of the types of labyrinthine
deformity. (From Phelps & Stansbie 1993, with
permission.)

22. • Fig. 52.13 Line drawings based on axial CT
sections of the types of labyrinthine
deformity. (From Phelps & Stansbie 1993, with
permission.)

23. • Fig. 52.13 Line drawings based on axial CT
sections of the types of labyrinthine
deformity. (From Phelps & Stansbie 1993, with
permission.)

24. • Fig. 52.14 Two basal CT sections showing a
normal basal turn of cochlea (A) and distal sac
(B), i.e. a true Mondini deformity. Some hearing
was present and the normal basal turn suggests
no risk of fistula or meningitis.

25. • Fig. 52.15 Congenital malformations of the middle
and external ears, based on corona! section
tomograms. (A) Normal. (B) Sloping external meatus.
(C) Pneumatised atretic plate with ossicular mass fixed
to it. (D) Thin atretic plate. (E) Small middle ear cavity,
spidery ossicles, and facial nerve canal exits through
the atretic plate (arrow). (F) Depressed tegmen
(arrow), lower part of middle ear only present, and
anterior position of the facial nerve (crossed arrow).
(From Phelps et al 1977.)

26. • Fig. 52.15 Congenital malformations of the middle and
external ears, based on corona! section tomograms. (A)
Normal. (B) Sloping external meatus. (C) Pneumatised
atretic plate with ossicular mass fixed to it. (D) Thin atretic
plate. (E) Small middle ear cavity, spidery ossicles, and
facial nerve canal exits through the atretic plate (arrow). (F)
Depressed tegmen (arrow), lower part of middle ear only
present, and anterior position of the facial nerve (crossed
arrow). (From Phelps et al 1977.)

27. • Fig. 52.15 Congenital malformations of the middle and
external ears, based on corona! section tomograms. (A)
Normal. (B) Sloping external meatus. (C) Pneumatised
atretic plate with ossicular mass fixed to it. (D) Thin atretic
plate. (E) Small middle ear cavity, spidery ossicles, and
facial nerve canal exits through the atretic plate (arrow). (F)
Depressed tegmen (arrow), lower part of middle ear only
present, and anterior position of the facial nerve (crossed
arrow). (From Phelps et al 1977.)

28. • Fig. 52.16 Coronal CT section at the level of the
cochlea showing typical appearances of
hemifacial microsomia on the left with
depression of the floor of the middle cranial fossa
(open arrow), anterior descending portion of the
facial nerve (black arrow), and deformity of the
left temporomandibular joint.

29. • Fig. 52.17 Bilateral metal atresia shown by
two coronal CT sections. There are small
middle ear cavities, and some hypoplastic
ossicles can be identified (black arrow). The
tegmen is depressed unilaterally and the
descending facial canal (white arrow) is at the
level of the oval window.

30. • Fig. 52.18 Two different but important vascular anomalies which
can be diagnosed on base CT sections, although further imaging in
the coronal plane is desirable. (A) Aberrant internal carotid artery
(c) in the middle ear (arrow). (B) Large jugular bulb (j), partially
dehiscent, in the middle ear cavity. Compare with the normal side
in each case.

31. • Fig. 52.19 Longitudinal fracture of the petrous temporal
bone with a depressed fragment of squamous temporal.
The fracture line runs along the roof of the external meatus
and middle ear with a small fragment of bone in the region
of the genicular ganglion (white arrow). The fracture
passed through the sphenoid sinuses which are filled
(asterisk). On the left side the black arrow indicates the
malleus in normal position; the incus was displaced. Axial
CT scan.

32. • Fig. 52.20 (A) Transverse fracture of the
pyramid passing through the vestibule
(arrow). Note the air in the cranial cavity and
the CSF level in the middle ear. (B) Plain
Stenver's view showing the fracture line
(arrow).

33. • Fig. 52.21 Coronal CT scan showing massive incus
displacement following a road traffic accident.
The images of the ossicles are completely
separate and the incus is lying inverted in the
attic (arrow).

34. • Fig. 52.22 Axial CT scan showing fluid in the
mastoid cell system on the left (arrow), with
cell wall breakdown.

35. • Fig. 52.23 Axial CT scan
through the basal turn
of the cochlea. On one
side a single channel
cochlear implant has
been inserted in the
round window (large
arrow); on the other side
there is labyrinthitis
obliterans with only the
hook of the basal turn
readily apparent (small
arrow).

36. • Fig. 52.24 Axial T2 -weighted MR section of the inner
ear in a patient for cochlear implantation. The basal
coil of the cochlea on the right shows high signal from
the medial part but low signal laterally, presumably
due to fibrosis (arrow) so insertion of the electrode
was unsuccessful. The basal turn on the left shows
uniform high signal and was subsequently implanted
without difficulty.

37. • Fig. 52.25 (A) Axial CT section showing an expansile
lesion in the petrous apex (asterisk). This was a
presumed cholesterol granuloma following trauma.
Note the good pneumatisation of the petrous apex on
the other side. (B) High signal on both T 1 - and T2 -
weighted MR protocols confirmed that this was a
cholesterol granuloma.

38. • Fig. 52.26 Corona! CT section at the level of the
vestibule showing a typical acquired
cholesteatoma which has eroded both the outer
attic wall (arrow) and the apex of the lateral
semicircular canal (open arrow) to give a positive
fistula sign clinically.

39. • Fig. 52.27 Corona! CT section showing an attic
cholesteatoma which has pushed the malleus (large
arrow) against the lateral attic wall, but also eroded
around the labyrinth and into the top of the cochlea.
The exposed central spiral of the cochlea is shown. The
asterisk marks the carotid canal.

40. • Fig. 52.28 A small osteoma of the middle ear arising
from the posterior aspect of the promontory close to
the round window. (A) Coronal tomogram shows the
osteoma just below the incudostapedial joint. (B) Axial
CT also shows the relation to the basal turn of the
cochlea.

41. • Fig. 52.29 (A) Base CT at
the level of jugular fossa
(j) and horizontal carotid
canal (a). On the right the
crest of bone between
them is apparent. On the
left this part of the
jugular fossa is eroded by
a glomus jugulare tumour
(arrow), which has also
extended into the middle
ear. (B) Base Gd-MR scan
at the same level,
showing the tumour
surrounding the carotid
artery and quite distinct
from the fluid in the
mastoid.

42. • Fig. 52.30 Sagittal Gd-MR scan showing a large glomus jugulare
tumour and its upper and lower limits in the posterior cranial fossa
and neck (arrows). The black streaks representing blood vessels are
characteristic. Gadolinium enhancement, although giving improved
differentiation in the mastoid and cranial cavity, is not such an
advantage in the neck, where adjacent fat also gives a bright signal
on a T 1 -weighted image. The open arrow points to the IAM.

43. • Fig. 52.31 (A) Coronal CT showing a small glomus
tympanicum in the lower middle ear cavity (arrow). J =
jugular bulb. (B) An equivalent MR section confirms
that this is quite separate from flowing blood in the
jugular bulb (J). Note the confusing proximity of
marrow fat (M).

44. • Fig. 52.32 (A) Axial CT section through the IAM
showing expansion of the first part of the facial nerve
canal (arrow). Note the calcification which should have
suggested that this was a haemangioma rather than a
neuroma. (B) Axial MR section, T 1 -weighted with
gadolinium enhancement, shows the mass (arrow).

45. • Fig. 52.33 Diagrams based on coronal section
tomograms. (a) The nerves in the normal IAM
passing from brainstem to labyrinth; (b)
intrameatal, (c) extrameatal, and (d) large
acoustic neuromas. V = trigeminal nerve. (From
Phelps & Lloyd 1983.)

46. • Fig. 52.33 Diagrams based on coronal section
tomograms. (a) The nerves in the normal IAM
passing from brainstem to labyrinth; (b)
intrameatal, (c) extrameatal, and (d) large
acoustic neuromas. V = trigeminal nerve.
(From Phelps & Lloyd 1983.)

47. • Fig. 52.34 Large acoustic neuroma in the left
cerebellopontine angle (asterisk). (A) Fast
spin-echo T2 axial section. (B) Equivalent T 1
section after gadolinium enhancement.

48. • Fig. 52.35 Corona! Gd-MRI showing bilateral
intrameatal acoustic neuromas (small arrows)
and a trigeminal neuroma (large arrow) in a
patient with neurofibromatosis (NF2).

49. • Fig. 52.36 (A) Axial FSE section showing a
small acoustic neuroma in the right IAM just
protruding into the cerebellopontine angle.
Note the normal nerves in the left IAM. (B)
Equivalent corona! T 1 section after
gadolinium enhancement.

50. • Fig. 52.37 (A) Axial Gd-MRI showing a large acoustic
neuroma in the cerebellopontine angle and medial
part of the IAM. (B) The bulk of the tumour has been
removed but a small segment adherent to the facial
nerve has been left deliberately (arrow) to preserve
facial nerve function and will be monitored for growth
on subsequent scans. Note the 'hole' in the posterior
cranial fossa.

51. • Fig. 52.38 (A,B) Coronal T 1 -weighted MR
with gadolinium enhancement showing a
meningioma of the posterior cranial fossa
extending into the IAM and jugular fossa as
well as onto the superior surface of the
petrous pyramid and into the tentorium
(arrows).

52. • Fig. 52.39 Ragged erosion of the right
mastoid region by a carcinoma shown on this
axial CT section.

53. • Fig. 52.40 Malignant otitis externa. Bone
destruction in the region of the mastoid (arrow)
around the internal carotid artery (a) and
temporomandibular joint (T) as well as sclerosis
of the basisphenoid (s) are shown on this axial CT
scan.

54. • Fig. 52.41 Axial CT with densitometry,
showing otospongiosis as a ring of rarefaction
around the cochlear coils. The densitometry
readings are mostly around 1200 HU. The
normal range is 1800-2400 HU.

55. • Fig. 52.42 Fibrous dysplasia, also affecting the
right mandible, is narrowing the right IAM and
external meatus. Such expansion of abnormal
bone may lead to cholesteatoma formation
behind the obstruction as here, but unlike Paget's
disease the otic capsule does not appear to be
affected by fibrous dysplasia.

56. • Fig. 52.43 Cross Paget's disease of the skull
base which is encroaching upon the
labyrinthine capsule on both sides. Only
remnants of normal capsular bone surround
the membraneous laybrinth in the cochlea
(arrow).