Hrct temporal bone pathology

1. HRCT TEMPORAL BONE IN
MIDDLE EAR PATHOLOGIES
PRESENTER : DR . SHAFREEN
MODERATOR : DR. SRINIVAS

2. HRCT temporal bone
 HRCT , is imaging modality that helps in evaluation of bone anatomy and
disorders of temporal bone .
 The air in the tympanic cavity surrounded by the dense temporal bone and the
mastoid air cells provide an inherent natural contrast to the HRCT imaging of
temporal bone and provides excellent delineation of bony land marks within the
temporal bone.
 HRCT provides higher spatial resolution and better soft tissue contrast.

4. Planes of Scanning :
 Axial plane :
 30 degrees to anthropological base line
 Parallel to lateral SCC.
 Best displays inner and middle ear
 Sections parallel to the hard palate
 Direct coronal plane:
 Plane is perpendicular to the lateral scc.
 Sections are parallel to posterior wall of maxillary sinus.
 Sagittal plane

5. Plane of stenvers

6. Plane of poschl

7.  The plane of poschl (in the same plane as the superior semicircular canal) and
the plane of stenvers (perpendicular to the Pöschl plane) are useful
reconstructions of the temporal bone in the assessment of the superior
semicircular canal.
 They are different from the coronal and sagittal reformats.
 The planes are also referred to as oblique coronals of the temporal bone.
 Given the structures are so small, a narrow detector and thin slice size are
advisable to image the temporal bone.
 Care must be taken to reconstruct in these planes for accurate interpretation and
reproducibility.

8. ANATOMY
 The temporal bones comprise the lateral skull base,
forming portions of the middle and posterior fossa.
 Each temporal bone is composed of five osseous parts:
 The squamous,
 Mastoid,
 Petrous,
 Tympanic, and
 Styloid portions.

10. Auditory appartus
 External ear :
Auricle and EAC
 Middle ear :
Epi tympanum , mesotympanum and hypotympanum
 Inner ear :
Osseous and membranous labyrinth

12. Temporal Bone Anatomy
 External Ear :
The external ear includes the auricle and external
auditory canal , which extends medially to the tympanic
membrane.
The tympanic membrane attaches to the tympanic
annulus and measures approximately 10 mm in
diameter.
 The normal tympanic membrane can often be faintly
discerned on CT images.

13. The lateral third of the EAC is fibrocartilagenous, while the
medial two-thirds of the EAC is surrounded by the tympanic
portion of the temporal bone .
Tympanic membrane makes angle of 55 degrees with the
floor of meatus.

14. Middle ear Anatomy
 Roof – Tegmen tympani
 Floor – Thin convex bone separating from the jugular
bulb
 Lateral wall – Tympanic membrane
 Medial wall – Separates inner ear
 Anteriorly – Auditory tube
 Posteriorly – Mastoid antrum

15. Middle ear
 Divided into three compartments in coronal
plane :
 A line drawn from the lower edge of the scutum
to the tympanic portion of facial nerve - Epi /
mesotympanum.
 Another line parallel to the floor of external
auditory canal – Meso / hypotympanum.

16. Epitympanum
 It contains :
 Head of malleus
 Malleo- Incudal articulation
 Body and short process of the incus
 Short process of incus projects posteriorly
towards the aditus.
 Best demonstrated on axial images.

17.  Tegmen tympani – roof of epitympanum
 Barrier between middle cranial fossa and
middle ear cavity .
 Best evaluated on coronal images.

18.  Posteriorly the epitympanum opens
into mastoid antrum via the aditus ad
antrum.
 Demonstrated on both the axial and
coronal images.

19. Mesotympanum
 The mesotympanum contanis the ossicular
chain
 Oval and round window
 Long process of the incus
 Stapes
 Handle of malleus
 Facial nerve canal

26. Medial wall

27. Anterior wall

29. HRCT TEMPORAL BONE IN MIDDLE
EAR PATHOLOGIES

30.  High resolution Computed tomography helps in assessing :
 The anatomical extension of infections and its complications,
 Detecting congenital abnormalities and
 Helps in detecting loss of surgical landmarks owing to previous surgeries.

31. Congenital malformations of external
and middle ear
 Development malformations affecting the external and middle ear results in conductive
hearing loss.
 Can be seen associated with syndromes like :
 A) CHARGE
 B) Klippe – fiel syndrome
 C)Trisomy 21

32. Congenital atresia of EAC

33. EAC Cholesteatoma

34. Keratosis obturans

35. Malignant Otitis Externa

36. Inflammatory condition of middle ear
 Otitis media : Inflammation of the middle ear . It can be acute or chronic.
 Acute otitis media : It is the most common condition affecting the middle ear.
 Acute otomastoiditis denotes infection of middle ear and mastoid.
 On CT :
 Soft tissue opacification of middle ear and mastoid air cells with or without air fluid levels .
 When the bony septae and mastoid cortex are destrcuted – Coalesecent mastoiditis .

37. Acute otitis media

38. Acute otomastoiditis

39. Coalesecent Mastoditis

41. Chronic otitis media
 Chronic otitis media is a form of otitis media where there is a prolonged
phase of inflammation in the middle ear with resultant tympanic membrane perforation.
 There are a few types of chronic otitis media :
 Benign / Inactive chronic otitis media : dry tympanic membrane perforation
 Chronic suppurative otitis media : purulent drainage through perforated tympanic
membrane
 Chronic otitis media with effusion : Serous drainage through the perforated tympanic
membrane.

42. Adhesive otitis media

44. Important complications :
 Coalescent mastoiditis ,
 Bezold abscess,
 Dural sinus thrombosis,
 Sub periosteal abscess ,
 Intracranial abscess and emphyema,
 Meningtis,
 Labrynthitis and
 Petrous apicitis

45. Bezold abscess

46. Petrous Apicitis

47. Epidural abscess

48. Cholesteatoma
 Both AOM and chronci otitis media can result in the development of aquired
cholesteatoma in the middle ear.
 A cholesteatoma is a sac lined with ectopic stratified squamous epithelium and
filled with exfoliated keratin debris.
 Most commonly arise in the pars flaccida region.
 Pars flaccida – Prussak space
 Pars tensa – Sinus tympani or fascial nerve recess.
 All types of cholesteatoma may erode the ossicular chain , scutum , mastoid
bone or korner’s septum.

53. Cholesterol Granuloma

56. FEATURES TO BE STUDIED ON
HRCT TEMPORAL BONE

57. THANK YOU