Transcript 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
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Squamous portion
Tympanic portion
Styloid process
Zygomatic process
Petromastoid portion which contain the
organs for hearing and equilibrium
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
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
Temporal Bones
 Mastoid process = conical process projecting
from mastoid portion
 Petrous portion projects medially and anteriorly
between greater wing of sphenoid and occipital
bone
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Also called petrous pyramid
Conical or pyramidal in shape
Thickest and densest portion of cranium
Contains the organs of hearing and balance
Temporal Bones
 Auditory ossicles = bones of middle ear
 Malleus
 Incus
 Stapes
 Temporal bone articulates with the
parietal, occipital, sphenoid, zygoma, and
mandible
Temporal Bones
Lateral view
Temporal Bones
Anterior view
Essential Projections:
Temporal Bone
 Axiolateral oblique (modified Law)
 Axiolateral oblique (Stenvers)
 Axiolateral oblique (Arcelin)
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
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
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
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
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
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
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
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
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