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Mastoids and Organs of Hearing

Mastoids and Organs of Hearing. Fall 2007. Ear. Temporal Bones. Situated on each side of cranial base between greater wings of sphenoid and occipital bone Form large part of middle cranial fossa and a small part of posterior cranial fossa. Temporal Bones. Consist of Squamous portion

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Mastoids and Organs of Hearing

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  1. Mastoids and Organs of Hearing Fall 2007

  2. Ear

  3. Temporal Bones • Situated on each side of cranial base between greater wings of sphenoid and occipital bone • Form large part of middle cranial fossa and a small part of posterior cranial fossa

  4. Temporal Bones • Consist of • Squamous portion • Tympanic portion • Styloid process • Zygomatic process • Petromastoid portion which contain the organs for hearing and equilibrium

  5. Temporal Bones • Tympanic portion = located below squama and in front of petromastoid portion • Forms anterior wall, inferior wall and part of posterior walls of the EAM • Styloid process = slender, pointed bone projecting inferiorly, anteriorly, and slightly medially from inferior surface of tympanic portion

  6. Temporal Bones • Petromastoid portion combines petrous and mastoid portions • Forms the inferior, posterior part of the temporal bone • Articulates with parietal bone at its superior border and with occipital bone at its posterior border • Usually contains air cells, which vary greatly in size, number, and pneumatization

  7. Temporal Bones • Mastoid process = conical process projecting from mastoid portion • Petrous portion projects medially and anteriorly between greater wing of sphenoid and occipital bone • Also called petrous pyramid • Conical or pyramidal in shape • Thickest and densest portion of cranium • Contains the organs of hearing and balance

  8. Temporal Bones • Auditory ossicles = bones of middle ear • Malleus • Incus • Stapes • Temporal bone articulates with the parietal, occipital, sphenoid, zygoma, and mandible

  9. Temporal Bones Lateral view

  10. Temporal Bones Anterior view

  11. Essential Projections: Temporal Bone • Axiolateral oblique (modified Law) • Axiolateral oblique (Stenvers) • Axiolateral oblique (Arcelin)

  12. Axiolateral Oblique (Modified Law) • Prone or seated upright • Tape auricle forward • Place head in true lateral position with affected side closer to IR • IOML parallel with IR • IPL perpendicular to IR • MSP angled 15 degrees toward IR

  13. Axiolateral Oblique (Modified Law) • CR • Angled 15 degrees caudad to midpoint of IR • Exits mastoid tip closer to IR about 1 (2.5 cm) posterior to EAM • Enters 2 (5 cm) posterior to and superior to upper EAM

  14. Axiolateral Oblique (Stenvers) • Prone or seated upright • Rest head on forehead, nose, and cheek with side of interest on IR • IOML parallel with transverse axis of IR • MSP at 45-degree angle from IR

  15. Axiolateral Oblique (Stenvers) • CR • Angled 12 degrees cephalad • Enters about 3 to 4 (7.6 to 10 cm) posterior and ½ (1.3 cm) inferior to upside EAM • Exits 1 (2.5 cm) anterior to downside EAM • IR and CR centered

  16. Axiolateral Oblique Temporal Bone (Arcelin) • Supine • MSP centered to midline • Rotate face away from side of interest to place MSP at 45-degree angle with plane of IR • IOML perpendicular to IR

  17. Axiolateral Oblique Temporal Bone (Arcelin) • CR • Angled 10 degrees caudad • Enters temporal area at 1 (2.5 cm) anterior to EAM and ¾ (1.9) cm above it • Center IR and CR

  18. Axiolateral Oblique Temporal Bone (Modified Law) • Mastoid process closer to IR • Air cells centered to IR • Opposite mastoid process inferior and anterior mastoid of interest • Auricle of ear not superimposing mastoid • Superimposition of IAM and EAM • TMJ visible anterior to mastoid process • Close beam restriction

  19. Axiolateral Oblique Temporal Bone (Stenvers) • Petromastoid portion in profile • Lateral border of skull to lateral border of orbit • Petrous ridge extended to a point about two thirds up lateral border of orbit Mastoid process in profile below cranium • Posterior margin of mandibular ramus superimposing lateral border of C-spine • Mandibular condyle projecting over atlas near petrosa • Close beam restriction

  20. Axiolateral Oblique Temporal Bone (Arcelin) • Petromastoid portion in profile • Lateral border of skull to lateral border of orbit • Petrous ridge lying horizontal about two thirds up lateral border of orbit Mastoid process in profile below cranium • Posterior margin of mandibular ramus superimposing lateral border of C-spine • Mandibular condyle projecting over atlas near petrosa • Close beam restriction

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