1. Mastoids and Organs of Hearing
Fall 2009

13. Ear

15. Temporal Bone

16. Temporal Bones
Situated on each side of cranial base between ____________and occipital bone
Form large part of ______ cranial fossa and a small part of ________ cranial fossa

17. Temporal Bones Consist of Squamous portion Tympanic portion
Styloid process
Zygomatic process
Petromastoid portion
a) contains the organs for ___________________

18. 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

19. 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

20. 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

21. Temporal Bones Auditory ossicles = bones of middle ear1. 2. 3.
Temporal bone articulates with the parietal, occipital, sphenoid, zygoma, and mandible

22. Temporal Bone Pathology
Mastoiditis
Neoplasms
Acoustic neuroma
Cholesteatoma
Polyp
Otosclerosis

23. Mastoiditis

24. Acoustic neuroma

25. Cholesteatoma

26. Essential Projections: Temporal Bone
Axiolateral oblique (Modified Law)
Axiolateral oblique (Stenvers)
Axiolateral oblique (Arcelin)

27. Axiolateral Oblique (Modified Law)
IOML ______with IR
IPL _________ to IR
MSP angled 15 degrees toward IR

28. 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

29. 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

30. Axiolateral Oblique (Stenvers)
IOML ________with transverse axis of IR
MSP at ________angle from IR

31. 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

32. 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

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

34. 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

35. 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