High Resolution Computer TomographyTEMPORAL BONE Pathology.pptx
- 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
- 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
- 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 .
- 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.
- 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.
- 56. FEATURES TO BE STUDIED ON HRCT TEMPORAL BONE
- 57. THANK YOU