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CT Imaging of the Temporal Bone: an anatomical review with illustrative cases of Cholesteatomas
Dunia Abdul-Aziz, HMS IIIDr. Gillian LiebermanBeth Israel-Deaconess RadiologyMay 19, 2008
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Outline
Review of the Normal Ear Anatomy
Tympanic Membrane
Middle Ear Cavity
Ossicular Chain
Spaces
Walls
Characteristic CT of the Normal Temporal Bone
Axial
Coronal
Cholesteatoma: Illustrative Pathology on CT
Patient presentation
Overview of cholesteatoma
Diagnosis, Pathogenesis, Differential, Management
Selected cases from companion patients
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Human Ear
Netter FH, 2003
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Human EarExternal Ear
Netter FH, 2003
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Human EarMiddle Ear
Netter FH, 2003
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Human EarInner Ear
Netter FH, 2003
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Middle Ear Anatomy
Air-containing space
communicates with the nasopharynx via the eustachian tube.
normally sealed laterally by TM.
Function:
transmission and amplification of sound from TM to stapes footplate.
Anderson JF, 1983
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Spaces of the Middle Ear
Middle Ear divided into five spaces based on relationship to tympanic annulus.
Epitympanum (Attic) - superior to annulus
Contains: body of incus and head of malleus.
communicates with the mastoid via aditus.
Mesotympanum - on level with the TM
Contains:
oval and round windows
long process of incus, articulation with stapes.
facial nerve in bony canal
Hypotympanum – below annulus
Contains: jugular bulb
Protympanum - in anterior recess of the middle ear
Contains: eustachian tube
Retrotympanum – posterior to annulus
Contains: sinus tympani, facial recess
Anderson JF, 1983
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Inside the Middle Ear: Ossicular
Chain
Lalwani AK, 2004
Malleus: long process (manubrium), short process, head
Tensor tympani m.
Incus: short process, long process
Lenticular process: distal portion of long process
Most tentative blood supply susceptible to resorption in otitis media
Stapes: Superstructure and footplate
Stapedius m.
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Walls of Middle Ear (Tympanic) Cavity
Agur AM, 1999
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Walls of Tympanic Cavity: Roof and Floor
Roof: tegemen tympani
Floor: Superior bulb of internal jugular v.
Agur AM, 1999
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Walls of Tympanic Cavity: Lateral
Lateral:•TM, malleus handle
Roof: tegemen tympani
Floor: Superior bulb of internal jugular v.
Grant’s Atlas, 1999
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Walls of Tympanic Cavity: Medial
Lateral:•TM, malleus handle
Roof: tegemen tympani
Floor: Superior bulb of internal jugular v.
Medial:•Promontory•Oval window--stapes•Round window (inferiorly)
Agur AM, 1999
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Walls of Tympanic Cavity: Posterior
Lateral:•TM, malleus handle
Roof: tegemen tympani
Floor: Superior bulb of internal jugular v.
Medial:•Promontory•Oval window--stapes•Round window (inferiorly)
Posterior:•aditus ad antrum: epitympanic recess
mastoid cells. •pyramidal eminencestapedius m.•Chorda tympani n. aperture
Agur AM, 1999
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Walls of Tympanic Cavity: Anterior
Lateral:•TM, malleus handle
Roof: tegemen tympani
Floor: Superior bulb of internal jugular v.
Medial:•Promontory•Oval window--stapes•Round window (inferiorly)
Posterior:•aditus ad antrum: epitympanic recess
mastoid cells. •pyramidal eminencestapedius m.•Chorda tympani n. aperture
Anterior: tensor tympani m.eustachian tube.
Agur AM, 1999
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Walls of Tympanic Cavity
Lateral:•TM, malleus handle
Roof: tegemen tympani
Floor: Superior bulb of internal jugular v.
Medial:•Promontory•Oval window--stapes•Round window (inferiorly)
Posterior:•aditus ad antrum: epitympanic recess
mastoid cells. •pyramidal eminencestapedius m.•Chorda tympani n. aperture
Anterior: tensor tympani m.eustachian tube.
Agur AM, 1999
Let’s take another look inside the Tympanic cavity by cutting
through the cavity in this plane…
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Middle Ear Anatomy: An additional view
Netter FH, 2003
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CT imaging of the temporal bone
Axial View
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Axial Slice (Superior to Inferior)
• The following slides are representative axial slices through the normal temporal bone, proceeding inferiorly from the most superior cut (through the superior semicircular canal).
Axial View Coronal ViewP I
SA
Silver JA et al. 1987
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Axial: Superior slice
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: Superior SCC
Superior SCC:
perpendicular to long axis of temporal bone
Superior petrosal sinus:
receives blood from cavernous sinus, drains to transverse sinus
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: Epitympanum
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Epitympanum: space above TM annulus (ring)
What do the structures in the box resemble?
Ice cream cone!
Correspond to ossicles: malleus head, incus body
Axial: Epitympanum
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Epitympanum: space above TM annulus (ring)
What do the structures in the box resemble?
Ice cream cone!
Correspond to ossicles: malleus head, incus body
Axial: Epitympanic
Structures
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Epitympanum: space above TM annulus (ring)
What do the structures in the box resemble?
Ice cream cone!
Correspond to ossicles: malleus head, incus body
Axial: Epitympanum
“ice cream”
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Epitympanum: space above TM annulus (ring)
What do the structures in the box resemble?
Ice cream cone!
Correspond to ossicles: malleus head, incus body
Axial: Ossicles
in the Epitympanum
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Anterior genu (ag):
first turn of the facial nerve
labyrinthine segment in fallopian canal (fc) turns to tympanic segment.
Axial: Anterior Genu
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Anterior genu (ag):
first turn of the facial nerve
labyrinthine segment in fallopian canal (fc) turns to tympanic segment.
Axial: Course of the Anterior Genu
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Facial nerve: Anterior genu
Anterior geniculate/First genu
Labyrinthine segment
curls anteriorly over cochlear terminates at geniculate
Tympanic segment
courses from 1st (anterior) to 2nd (posterior) genu.
underneath horizontal SCC and superior to oval window
can be identified using short process of the incus as landmark. (box)
1st genu
2nd genu
Gaillard F. http://www.radiopaedia.org/index.php?title=Facial_nerve_(CN_VII)
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Axial: moving inferiorly…
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: IAC outlined
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Internal auditory canal (IAC) PFN SV
C IVA
Axial: Internal auditory canal
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Internal auditory canal (IAC)
Note:
Structures anterior to IAC are cochlear
PFN SV
C IVA
Axial: relationship of IAC to cochlea
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Internal auditory canal (IAC)
Note:
Structures anterior to IAC are cochlear
Structures posterior to IAC are vestibular
PFN SV
C IVA
Axial: relationship of IAC to vestibular system
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: Characteristic landmark
What do the structures in the box resemble?
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: “Signet Ring”
What do the structures in the box resemble?
Signet ring!
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: Vestibule and LSCC
What do the structures in the box resemble?
Signet ring!
Corresponds to Vestibule and LSCC
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Vestibular aqueduct:
bony canal that passes to posterior fossa dura
Opens lateral to IAM
transmits endolymphatic duct and 2 blood vessels into blind sac (reservoir for excess endolymph)
Common crus: union of superior and posterior SC ducts.
Axial: Vestibular Aqueduct
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Note:
The relationship of the incus (short process) to help identify facial n. (tympanic segment)
Axial: Relationship of Incus
(short process) to the Facial n.
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Axial: moving inferiorly…
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Review: Middle Ear Cavity Superiorly
Netter FH, 2003.
Medial wall of Tympanic cavity
Round Window Promontory
Eustachian tube
Tensor tympani m.
Prominence of Lateral SCC
A section through this plane will thus reveal the tensor tympani m., lateral SCC and stapes.
Stapes
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Tensor tympani m.:
arises from cartilaginous and bony margins of eustachian tube
inserts on handle of malleus
Dampens ossicular chain
Lateral SCC
Stapes
Axial: Tensor tympani canal
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Review: Middle Ear Cavity Illustration
Netter FH, 2003.
Medial wall of Tympanic cavity
Round Window Promontory
Eustachian tube
Tensor tympani m.
Prominence of Lateral SCC
A section through this plane will thus reveal the round window, promotory and eustachian tube
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Axial: Middle Ear Cavity
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Round window:
opening between middle and inner ear, associated with scala tympani
below oval window
Promontory:
medial wall of tympanic cavity formed by basal turn of cochlea
Axial: Round Window
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
Promontory Promontory
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Axial: continuing to move inferiorly…
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Facial nerve (mastoid segment, ms), here it gives off:
Chorda tympani (ct):
taste fibers to anterior 2/3 tongue
preganglionic parasympathetic to submandibular & sublingual glands
Courses between incus and handle of malleus
Agur AM, 1999.Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
Axial
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Axial: Inferior view, facial n.
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Facial nerve (mastoid segment, ms)
Courses from second genu to the stylomastoid foramen
Gives off 3 branches:
Nerve to stapedius (ns)
Chorda tympani (ct)
nerve from the auricular branch of vagus (pain fibers to posterior auditory canal)
Axial: Facial nerve branches
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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CT imaging of the temporal bone
Coronal View
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Coronal Slice (Posterior to Anterior)
Axial View Coronal ViewP I
SA
Silver JA et al. 1987
• The following slides are representative coronal slices through the normal temporal bone, proceeding anteriorly from the most posterior cut (through the semicircular canals).
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Coronal: Semicircular Canals (posteriorly)
Posterior, Lateral and Superior SCC
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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90° angle between Lateral and Superior SCC
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
Coronal: Semicircular Canal Relationship
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Coronal: more anteriorly, the vestibule is visualized:
Vestibule: union of Superior and Posterior SC ducts.
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal: continuing anteriorly
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal: External auditory canal
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
External Auditory Canal External Auditory Canal
External Auditory Canal
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Coronal: Scutum
Scutum: spur-shaped bony projection top of tympanic membrane
Often eroded by cholesteatoma
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal: Tympanic Membrane
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
Outline of Tympanic Membrane
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Coronal: Prussak’s space
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal: Prussak’s space
Prussak’s space: anterior recess of TM, between neck of malleus and pars flaccida of tympanic membrane
*most common site of acquired attic cholesteatoma. Prussak’s space (pars flaccida (lateral border) removed)
Gulya JA, 1995.
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal
Observe:
Cochlea “snail”
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.comAnderson JF, 1983
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Coronal
Observe:
Cochlea “snail”
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.comAnderson JF, 1983
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Coronal
Observe:
Cochlea “snail”
Two low attenuating areas above
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.comAnderson JF, 1983
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Coronal
Observe:
Cochlea “snail”
Two low attenuating areas above
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.comAnderson JF, 1983
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Coronal
Snake’s eyes: Snake’s eyes:
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
“snake eyes”: distal labyrinthine and proximal tympanic segments of facial nerve.
Locate anterior to the “snail” (cochlea)
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Coronal
Question: How can the facial nerve appear twice in a single coronal slice?
Snake’s eyes: Snake’s eyes:
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal
Question: How can the facial nerve appear twice in a single coronal slice?
Answer: facial nerve turns at the anterior genu (turn)!
Gaillard F. http://www.radiopaedia.org/index.php?title=Facial_nerve_(CN_VII)Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Coronal: Anterior genu
Anterior genu
Fatterpekar et al., 3D CT of the temporal bone. www.terarecon.com
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Patient Presentation
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Patient 1: HPI
S. A. is a 32 year old male with left-sided hearing loss and foul smelling otorrhea for 2 months.
No otalgia, dizziness or tinnitus.
PMH: Frequent ear infections as a child.
Medications/Allergies: None
FH: negative for hearing loss or ear abnormalities.
Physical Exam:
Weber localizes to left.
Rinne:
Right: AC>BC
Left: BC>AC (abnormal)
Facial nerve intact
Otoscopic Exam:
Audiometry: Left conductive hearing deficit.
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Patient 1: PMH/Meds/Allergies/FH
S. A. is a 32 year old male with left-sided hearing loss and foul smelling otorrhea for 2 months.
No otalgia, dizziness or tinnitus.
PMH: Frequent ear infections as a child.
Medications/Allergies: None
FH: negative for hearing loss or ear abnormalities.
Physical Exam:
Weber localizes to left.
Rinne:
Right: AC>BC
Left: BC>AC (abnormal)
Facial nerve intact
Otoscopic Exam:
Audiometry: Left conductive hearing deficit.
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Patient 1: Physical Exam
S. A. is a 32 year old male with left-sided hearing loss and foul smelling otorrhea for 2 months.
No otalgia, dizziness or tinnitus.
PMH: Frequent ear infections as a child.
Medications/Allergies: None
FH: negative for hearing loss or ear abnormalities.
Physical Exam:
Weber Test localizes to left.
Rinne Test:
Right: AC>BC
Left: BC>AC (abnormal)
Facial nerve intact.
Audiometry: Left conductive hearing deficit.
Otoscopic Exam:
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Patient 1: Otoscopic
Exam
S. A. is a 32 year old male with left-sided hearing loss and foul smelling otorrhea for 2 months.
No otalgia, dizziness or tinnitus.
PMH: Frequent ear infections as a child.
Medications/Allergies: None
FH: negative for hearing loss or ear abnormalities.
Physical Exam:
Weber localizes to left.
Rinne:
Right: AC>BC
Left: BC>AC (abnormal)
Facial nerve intact
Audiometry: Left conductive hearing deficit.
Otoscopic Exam:
Roland PS. http://www.emedicine.com/ent/topic220.htm
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Patient 1: CT of Left Temporal Bone (coronal view)
Coronal C- CT, Left ear
PACS, MEEI. Courtesy of Dr. Hines-Parelta
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Patient 1: Describe the lesion
Coronal C- CT, Left ear
PACS, MEEI. Courtesy of Dr. Hines-Parelta
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Patient 1 CT Evaluation: Start with a Comparison
Compare to Right Ear (normal)!
PACS, MEEI. Courtesy of Dr. Hines-Parelta
Coronal C- CT, Right ear (normal) Coronal C- CT, Left ear
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Patient 1 CT Evaluation: Familiar findings
Compare to Right Ear (normal)!
Observe:
Cochlea “snail”
Snake’s eyes: labyrinthine and tympanic segments of facial nerve
PACS, MEEI. Courtesy of Dr. Hines-Parelta
Coronal C- CT, Right ear Coronal C- CT, Left ear
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Right ear:
normal scutum
Prussak’s space
ossicles in epitympanum.
PACS, MEEI. Courtesy of Dr. Hines-Parelta
Coronal C- CT, Right ear Coronal C- CT, Left ear
Patient 1 CT Evaluation: Right ear
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PACS, MEEI. Courtesy of Dr. Hines-Parelta
Patient 1 CT Evaluation: Left ear
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Patient 1: Temporal Bone CT: Axial Views
PACS, MEEI. Courtesy of Dr. Hines-Parelta
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Patient 1: Axial CT evaluation: Right ear
PACS, MEEI. Courtesy of Dr. Hines-Parelta
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Axial View
PACS, MEEI. Courtesy of Dr. Hines-Parelta
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Patient 1: Diagnosis and Management
Diagnosis: Acquired Cholesteatoma
Patient’s presentation, physical exam/otoscopic findings consistent with Acquired Cholesteatoma.
CT findings of soft tissue mass with bony erosion support diagnosis of Cholesteatoma and illustrate the extent of disease.
Management:
S.A. underwent tympanomastoidectomy for removal of the cholesteatoma
no evidence of recurrence to date.
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Cholesteatoma: Overview
Benign epidermoid cyst of the middle ear or mastoid
“Skin in the wrong place”
Prone to recurrent infection
Grows progressively as it accumulates epithelial debris
Progressive erosion of bone of ossicles and otic capsule
Incidence:
estimated 3 in 100,000 (children) and 9 in 100,000 (adults)
http://www.marshfieldclinic.org/patients/Default.aspx?page=ent_ear_cholesteatoma
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Clinical Presentation
Hallmark: chronic otitis, painless otorrhea, conductive hearing loss.
Persistent/recurrent despite antibiotics
difficult to treat (lack of blood supply)
Hearing loss
Middle ear space filled with desquamated epithelium +/- mucopurulent discharge
ossicular damage.
Occasionally present with complications of cholesteatoma:
Dizziness and hearing loss (labyrinthine fistula)
Facial nerve paralysis
Intracranial infection
Sigmoid sinus thrombosis
Epidural abscess
Meningitis
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Pathology
Histology:
Perimatrix: granulation tissue
secrete proteolytic enzymes
Matrix: keratinizing squamous cell epithelium
Cystic: keratin filled center
Mechanism of bone erosion:
Mechanical:
pressure effects of growing mass induce bony remodeling
Biochemical:
bacterial elements (endotoxin)
host inflammatory mediators and enzymes
Dornelles, C. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0034-72992005000400023&lng=en&nrm=iso
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Etiology
Three subtypes of Cholesteatomas reported
Congenital
Primary acquired
Secondary acquired
Differ in presentation, pathogenesis and natural history.
At least four theories have been proposed to explain the pathogenesis of acquired cholesteatomas, with different theories predominating in primary vs. secondary acquired cholesteatomas.
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Congenital Cholesteatoma
Rare: 2% of all cases of Cholesteatomas
Clinical presentation:
Mass behind intact/normal TM
Young child (6mo-5 years)
no history of recurrent infections/perforation.
M:F ratio= 3:1
Etiology: squamous epithelium rests trapped within temporal bone during embryogenesis.
Location: anterior mesotympanum, perieustachian tube area, petrous apex.
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Primary Acquired Cholesteatoma
Etiology: Eustachian tube dysfunction, negative middle ear pressure
Most common type: 82% of acquired cases
Location/Extension:
pars flaccida retraction into the epitympanum, erosion of scutum (lateral wall of epitympanum).
Posteriorly (most common): Prussak’s space epitympanum, lateral to incus body
Inferiorly: via pouch of von Tröltsch into the middle ear
Anteriorly: into the protympanum
Swartz JD, 1984
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Secondary Acquired Cholesteatoma
Etiology: secondary to TM injury
18% of acquired cases
posterior marginal perforation from otitis media, trauma, surgery
Extension route: pars tensa retracts into mesotympanum to form cholesteatoma
Ossicles displaced laterally
Can invade sinus tympani and facial recess
difficult to remove
Bailey BJ et al. 2006
Swartz JD, 1984
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Pathogenesis of Acquired Cholesteatomas
Four theories:
Imagination of the tympanic membrane (retraction pocket)
Epithelial ingrowths through a perforation (migration)
Basal cell hyperplasia
Squamous metaplasia of middle ear epithelium
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Negative pressure theory (primary acquired)
Eustacian tube dysfunction resulting in poor aeration and relative negative pressure in the middle ear
medial retraction of pars flaccida
progressive deeping of the retracted areas
pit formation and collection of epithelial debris
poor clearance of debris
encystment and cholesteatoma formation.
Cummings CW et al., 2005
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Migration theory (secondary acquired)
Chronic infection/ recurrent otitis media
Destruction of the marginal portion of pars tensa
in growth of epithelium from external auditory canal into middle ear through perforation
progressive deeping of the retracted areas
subsequent encystement and cholesteatoma formation.
Cummings CW et al., 2005
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Basal cell hyperplasia theory
Breaks in the basal lamina
invasion of epithelial cones into subepithelial connective tissue
Microcholesteatomas form and enlarge
perforate secondarily through the TM (resulting in classic appearing attic cholesteatoma)
Cummings CW et al., 2005
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Metaplasia theory
Middle ear infection/chronic inflammation
metaplasia of middle ear mucosa to stratified squamous epithelium secondary to middle ear infection
secondary TM perforation
subsequent encystement and cholesteatoma formation.
Cummings CW et al., 2005
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Cholesteatoma Subtypes: Summary
Primary Acquired Secondary Acquired Congenital
Frequency 98% 2%
82% 18%
Clinical Presentation Eustachian tube dysfunction
TM perforationHistory of infection, trauma or surgery
Child with mass behind intact TMNo history of chronic infection
Pathogenesis (theories) Negative middle ear pressure
Inward migration of squamous epithelium
Embryonic epithelial rests
Inflammation Noninflammed ear Inflammed ear Noninflammed ear
Tympanic membrane perforation
None, retraction pocket in pars flaccida
Marginal perforation in pars tensa
None
Location and direction of growth
Prussak’s spaceSuperiorly into antrumDisplaces ossicles medially
Inferior tympanumDisplaces ossicles laterally
Petrous apex, mastoid, middle ear.
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Diagnosis of Cholesteatoma
Roland PS. http://www.emedicine.com/ent/topic220.htm
Attic Cholesteatoma (early)
Middle Ear Cholesteatoma (advanced, destruction of landmarks)
Otoscopic Exam:
Canal filled with mucous and granulation tissue.
Yellowish mass eroding through TM
TM perforation > 90% cases
Exception: congenital cholesteatomas.
Audiometry:
Conductive hearing loss
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Role of Imaging in Diagnosis of Cholesteatoma
Diagnosis often made otoscopically
Radiologic imaging serves as adjunct:
Assess extent of disease
Evaluate complications:
chronic supportive otitis media (CSOM).
Suspected congenital abnormalities.
Loss of landmarks due to previous surgery.
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Characteristic Findings of Cholesteatoma on CT Imaging
CT without contrast:
Modality of choice:
identifies soft tissue masses and bony erosions
Findings:
nondependent soft tissue mass and bony erosion (80% specificity)
Can be difficult to distinguish cholesteatoma from granulation tissue, pus or fluid.
Often different pathologies related to chronic ear infection coexist
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Characteristic Findings of Cholesteatoma on MRI Imaging
MRI:
Advantage: differentiate cholesteatoma from surrounding fluid/inflammation
New reports suggesting role in post-surgical surveillance of recurrence
Limitation: poor visualization of bony landmark
Findings:
Medium signal intensity on T1-weighted images
High intensity on T2-weighted images
Nonenhancing (unless infiltrated with granulation tissue)
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Differential Diagnosis: Soft Tissue Mass in Middle Ear
Cholesteatoma*
Cholesterol Granuloma*
Chronic otitis media*
Globus tympanicum tumor
Granulation tissue
Malignant otitis externa
Neoplasm
Squamous cell carcinoma (adult)
Rhabdomyosarcoma (children)
* Can have accompanying bone erosion
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Complications: bone erosion and recurrent infection
Hearing loss:
conductive: erosion of ossicles (esp incus)
sensorineural: suppurative labyrinthitis or from the cochlear hair cell loss adjacent to cholesteatoma
Labyrinthine fistula: 10%
horizontal SCC most common
sensorineural hearing loss and vertigo
Facial nerve paralysis:
acute (infection) or chronic (compression from expanding cholesteatoma)
anterior geniculate most common
Dural involvement:
Intracranial infections, subdural/epidural abscess, sigmoid sinus thrombosis, brain hernia or cerebrospinal fluid leakage (erosion of tegmen tympani or tegmen mastoideum)
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Complications identified by CT imaging
The following slides are illustrative CT images from patients with Cholesteatomas that help to illustrates additional pathologies.
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Companion Patient 1: Tegemen
erosion
Extensive cholesteatoma
tegemen erosion; dura exposed
bony sclerosis obliterating cochlea
Yates PD et al., 2002.
Coronal C- CT, Right ear
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Companion Patient 2: Labyrinth Fistula
Extensive Cholesteatoma
Ossicular erosion
Labyrinth fistula (white arrow)
Erosion of bone covering lateral SCC.
Silver JA et al. 1987
Round window (black arrow)
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Companion Patient 3: Erosion of Facial n. canalObserve:
Familiar Landmarks:
Cochlea “snail”
“Snake’s eyes”: tympanic and labyrinth segments of facial n.
Pathology:
1.epitympanic cholesteatoma
Erosion of tegmen tympani, scutum, ossicles
2. erosion of bony canal of facial nerve
Waizel, S. http://www.emedicine.com/RADIO/topic676.htm
Erosion of facial n. canal
Coronal C- CT, Right ear
Comparison: Coronal C- CT, Left ear, Normal
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Companion Patient 4: Identify the Structure
PACS, MEEI. Courtesy of Dr. Hines-Parelta
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Companion Patient 4: TORP
Total ossicular replacement prosthesis (TORP)
http://www.kbbmnt.com/torpporp.html
PACS, MEEI. Courtesy of Dr. Hines-Parelta
TORP:
positioned between stapes footplate and tympanic membrane.
prosthesis is placed perpendicularly to footplate to ensure optimum sound transmission.
Axial C- CT, Left ear
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Companion Patient 4: Hearing Loss s/p TOPR
10-year-old male with a congenital cholesteatoma (left) s/p removal with TORP.
Now with decreased hearing for 2 years.
Evaluate for recurrence.
PACS, MEEI. Courtesy of Dr. Hines-Parelta
Axial C- CT, Left ear
Axial C- CT, Left ear
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Companion Patient 4: Malpositioned Prosthesis
10-year-old with a congenital cholesteatoma (left) s/p removal with TORP.
Now with decreased hearing for 2 years.
Evaluate for recurrence.
Observe:
No soft tissue mass/recurrence.
Thickened TM secondary to scarring.
Prosthesis displaced anteriorly and articulates mostly with bone adjacent to oval window.
PACS, MEEI. Courtesy of Dr. Hines-Parelta
Axial C- CT, Left ear
Axial C- CT, Left ear
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Management: Surgical Options
Surgery to remove Cholesteatoma is the mainstay of treatment.
Indication: eradication of disease, complications
Options:
Atticotomy: transcanal
Simple mastoidectomy
Tympanomastoidectomy:
Canal-wall-down procedure:
Bony partition between external ear canal and mastoid removed.
Outcome: enlarged meatus, difficult to fit hearing aids; low rate of persistant/recurrent dz, canal cleaning needed, can have problem with water exposure. single procedure.
Canal-wall-up procedure:
Bony parition intact.
Outcome: normal appearance, relatively high rate of recurrent/persistent dz, high tolerance for water exposure. Staged procedure to evaluate recurrence.
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Management: Conservative therapy
Conservative Therapy
Reserved for patients who are poor surgical candidates or refuse surgery
Regular ear cleaning
Topical microbial therapy +/- systemic therapy as adjunct
Helps control infection and may slow growth
Does not stop expansion
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Prognosis
Recurrent/residual cholesteatoma: 15 to 40% in 5 years
Canal wall up tympanomastoidectomies usually return to the OR for a “second look” in one year.
Regular follow up required.
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References
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References (continued)
Netter FH. Atlas of Human Anatomy. 3rd Edition. Icon Learning Systems. 2003.
Putz R, Pabst R (editors). Sobotto Atlas of Human Anatomy. Volume I: Head, Neck and Upper Limb. Lippincott Williams & Wilkins. 2000.
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Roland PS. Middle Ear, Cholesteatoma. eMedicine. 2006 http://www.emedicine.com/ent/topic220.htm Swartz JD. Cholesteatomas of the Middle Ear: Diagnosis, Etiology and Complications. Symposium on CT of the Ear, Nose and Throat. Radiologic Clinics of North America. Mar 1984. 22:1. p 15-35.
Silver JA, Janecka I, Wazen J, Hilal S, Rutledge JN. Complicated Cholesteatomas: CT Findings in Inner Ear Complications of Middle Ear Cholesteatomas. Radiology 1987; 164:47-51
Swartz JD et al. The temporal bone. Head and Neck imaging. Radiologic Clinics of North America. Sept 1998. 36:5.
Virapongse C, Bhimani S, Sarwar M. Radiography of the Normal Ear. Symposium on CT of the Ear, Nose and Throat. Radiologic Clinics of North America. Mar 1984. 22:1. p 1-11.
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Yates PD, Flood LM, Banerjee KC. CT scanning of middle ear cholesteatoma: what does the surgeon want to know? The British Journal of Radiology, 75 (2002), 847–852.
<http://www.meddean.luc.edu/lumen/MedEd/grossAnatomy/dissector/mml/tt.htm>
<http://www.radiopaedia.org/index.php?title=Facial_nerve_(CN_VII)>
<http://radsmd.com>