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Navigating the Temporal Bone and
IAC to Reveal Hearing Loss
Pathology: A Diagnostic Algorithm.
ASNR 2015
Presentation Number: eEdE-143
Rajesh Gupta MD
Ammar Chaudhry MD
Margaret Whelan MD
Luboslav Woroch DO
Robert Peyster MD
Disclosures
No disclosures to report.
Outline
• Overview Internal Auditory Canal (IAC) MRI
anatomy and search pattern with images
• Temporal bone CT search pattern with select
images
• Algorithms based on location and category
• Example Cases
IAC MRI Anatomy and Search Pattern :
3D CISS sequence (thin axial high T2 sequences)
Review axial images superior to inferior
Look at CN V and Meckel’s cave
Look at Petrous Apex
IAC MRI Anatomy and Search Pattern :
3D CISS sequence (thin axial high T2 sequences)
Look at the Cerebellopontine angle
Look at the IAC and evaluate it’s origin
IAC MRI Anatomy and Search Pattern :
3D CISS sequence (thin axial high T2 sequences)
Notice CN 7 & 8 in the IAC and
their close relationship to AICA
More inferiorly, evaluate the cochlear
and vestibular nerves
IAC MRI Anatomy and Search Pattern :
3D CISS sequence
Sagittal Multiplanar Reconstruction (MPR) through the IAC
(nerve anatomy within the canal)
Superior
Superior
Vestibular n.
Facial n
Falciform crest
Anterior
Cochlear n
Inferior
Vestibular n.
The IAC is divided superiorly and inferiorly by a bony lamina (falciform crest):
- Smaller superior part:
- Larger Inferior part:
- Superior vestibular n.
- Inferior vestibular n.
- Facial n
- Cochlear n.
Bill’s Bar divides the superior portion of the canal anterior to posterior
IAC MRI Anatomy and Search Pattern :
3D CISS sequence (thin axial high T2 sequences)
Finally:
Evaluate the following fluid filled
structures that are T2 bright:
•Semicircular canals
•Vestibule
•Ovoid in shape
•Cochlea
•Modiolus: hypointense area
at base
Click to Return to Outline
CT Temporal Bone Search Pattern with selected images :
Use both axial and coronal CT
images
e
Start from outside to in:
•EAC
•Scutum (s)
•Tympanic membrane (#)
•Epitympanum (e)
•Prussak’s space (*)
•Mesotympanum (m)
•Hypotympanum
•Pyramidal eminence (*)
•Sinus tympani (st - medially)
•Facial n. recess (fnr -laterally)
•Ossicles
•Malleus
•Incus
•Stapes
•Oval window
s
EAC
*
m
#
Cor
malleous
incus
stapes
fnr
*
st
Axial
CT Temporal Bone Search Pattern with selected images :
Use both axial and coronal CT
images
Otic capsule:
•Superior semicircular canal (SCC)
•Posterior SCC (P)
•Lateral SCC (L)
•Vestibule (v)
•Aditus ad antrum (A)
•Cochlea
•Modiolus (mo)
•Basal turn (b)
•Middle turn (m)
•Apical turn
•IAC
•Facial n.
•labyrinthine segment (Fnl)
•geniculate segment
•tympanic segment
•Vestibular aqueduct
Fnl
A
L
IAC
v
P
Axial
Fnl
mo
m
b
Cor
CT Temporal Bone Search Pattern with selected images :
Other structures/landmarks:
•Styloid process
•Stylomastoid foramen
•Petrous apex
•Mastoid air cells
•Sigmoid sinus
•Cochlear promontory
•Carotid canal
•Tegmen
•Jugular bulb
Tegmen
Petrous portion of
the temporal
bone
Cochelar
promontory
Carotid
canal
Cor
Click to Return to Outline
Sensorineural hearing loss algorithm (click on blue text to go to case)
Location
•Cochlea/semicircular canals – likely congenital
•Cochlear dysplasia – Incomplete Partition 1 and 2
•Enlarged vestibular aqueducts
•Enlarged vestibular aqueduct syndrome
•Common cavity malformation
•Labyrinth – abnormal mineralization
•Bony labyrinth with lytic foci – Otospongiosis (mixed hearing loss)
•Membranous labyrinth – Labyrinthitis ossificans
•Trauma – fracture (acquired)
•Cerebellopontine angle and/or Internal auditory canal
•Vestibular schwanoma
•Meningioma
•Epidermoid cyst
•Glomus tumor
•Lymphoma
•Sarcoid
•Brainstem
•Neoplasms
•Multiple sclerosis
Conductive hearing loss algorithm (click on blue text to go to case)
Location
•External Auditory Canal
•Congenital
•Atresia/stenosis
•Inflammatory
•Cholesteatoma
•Keratois obturans
•Neoplasm
•Exostosis, osteoma
•Squamous Cell
Carcinoma
•Infectious
•Otitis Externa
•Tympanic Membrane
•Perforation
•Chronic Inflammation
•Myringosclerosis
Location
•Middle Ear
•Congenital
•Ossicular anomalies
•Cholesteatoma
•Aberrant carotid artery
•Aberrant facial nerve
•Persistant stapedial artery
•Inflammatory
• Acquired Cholesteatoma
•Neoplasm
•Glomus tympanicum
•Facial neuroma
•Meningioma
•Infectious
•Otitis Media
•Trauma
•Ossicular disruption
•Hemotympanum
Click to Return to Begining
Selected Cases
Enlarged Vestibular Aqueduct Syndrome (EVAS) :
2 year old F with bilateral sensorineural hearing loss.
6mm
5 mm
A: CT Rt axial
B: CT Lft axial
Bilateral enlarged vestibular aqueducts are shown (yellow arrows). Measurements are
shown at the operculum (red lines). At the midpoint , between the crus and aperture, the
aqueducts measured 3 mm bilaterally.
Normal < 1.5 mm @ midpoint
Normal < 1.9 mm @ operculum
Click to Return to Algorithm
Common Cavity Malformation :
11 month old M with left sensorineural hearing loss.
Normal Cochlea
A: CT Rt axial
Normal:
Superior Semicircular canal,
Confluence of the cochlea, vestibule, and
semicirucular canals forming a common
cavity
C: CT Lft axial
Common cavity
Widened IAC
Vestibule, and
Basal turn of cochlea
B: CT Rt coronal
D: CT Lft coronal
Click to Return to Algorithm
Click to Return to Algorithm
Complex cholesterol granuloma :
19 year old M with sudden onset left sensorineural loss, severe vertigo and facial paralysis.
A: MR T1WI Pre-Contrast
B: MR T2WI
Figure A:– Large expansile T1 hyperintense lesion (yellow arrows) at the left petrous apex, jugular
foramen and IAC. The lesion involves the 7th and 8th cranial nerve complex leading to sensorineural
deafness. B – This lesion exhibits T2 hyperintensity (yellow arrows) and rim of T2 hemosiderin (white
arrow). On post contrast imaging, there was no central enhancement but faint peripheral enhancement.
The patient required trans-mastoid drainage with resolution of symptoms.
Vestibular Schwanoma :
44 year old M with left sensorineural hearing loss.
A: MR axial T2 FLAIR
B: MR axial T1 Post
C: MR cor T1 Post
Figure A: Heterogeneous, FLAIR hyperintense 4.8 cm extra-axial mass in the left
cerebellar pontine angle extending into the internal auditory canal with widening and
involvement of the vestibular n. (yellow arrow)
Figures B & C: Heterogeneous enhancement with central cavitation representing necrosis
(yellow arrows). There is mass effect on the pons and left cerebellum with stenosis of
upper 4th ventricle causing mild hydrocephalus.
Click to Return to Algorithm
Epidermoid :
48 year old F with left sensorineural hearing loss.
A: MR T1 axial
B: MR DWI axial
C: MR DWI axial
Figure A: Lesion at the cerebellopontine angle involving the left internal auditory canal
and nerve complex that is isointense to CSF on T1WI (yellow arrow).
Figures B & C: The lesion is hyperintense on DWI and dark on ADC (not shown) due to
restricted diffusion, without post contrast enhancement (not shown) suggesting the
diagnosis of an Epidermoid tumor over an arachnoid cyst (yellow arrows).
Click to Return to Algorithm
Internal Auditory Canal (IAC) Atresia :
5 year old M with left sensorineural hearing loss.
Absent
Lft IAC
Absent
Lft IAC
Normal
Rt IAC
A: MR axial T2 FLAIR
C: MR mip axial IAC
Normal
Rt IAC
B: MR axial T2
Absent
Lft IAC
Click to Return to Algorithm
Otospongiosis :
59 year old F with right mixed hearing loss.
No lucency
A: CT Rt axial
B: CT Lft axial
Figure A: Punctate focus of lucency in the region of the fistula antefenestrum (ie. In front
of the oval window) consistent with fenestral (stapedial) otospongiosis.
The retro-fenestral (cochlear) subtype is less common and involves demineralization of
the cochlear capsule.
Figure B: Normal left side for comparison.
Click to Return to Algorithm
Otitis Externa :
7 year old F with fever, left ear swelling, tenderness, erythema, discharge and
intermittent left sided conductive hearing loss.
A: CT Rt axial
B: CT Lft axial
Soft tissue attenuation
material within the external
auditory canal with
abnormal enhancement
(Fig C). Canal is obliterated
medially with extension into
the middle ear cavity.
Normal Rt
external ear
canal with small
focus of
cerumen.
C: CT Head post contrast axial
Click to Return to Algorithm
Congential Cholesteatoma :
2 year old M with left conductive hearing loss.
A: CT Rt axial
C: CT Lft axial
B: CT Rt cor
D: CT Lft cor
A 3 mm nodular soft tissue density (yellow arrows) is identified along the left tensor
tympani tendon and inferomedial to the malleus (manubrium). There is no associated
bony erosion differentiating it from acquired cholesteatoma. Normal right side shown
for comparison (Figures A &B)
Click to Return to Algorithm
Acquired Cholesteatoma :
39 year old F with left conductive hearing loss.
Clear
Middle
ear
cavity
A: CT Rt axial
C: CT Lft axial
Soft tissue density within the
middle ear cavity. It
obliterates Prussak’s space
and erodes the scutum and
ossicles.
Normal
Scutum
B: CT Rt cor
D: CT Lft cor
Click to Return to Algorithm
External Auditory Canal (EAC) Atresia :
14 year old M with right conductive hearing loss.
Absent EAC
Normal EAC
C: CT Lft axial
A: CT Rt axial
Small malleus and
middle ear cavity
Normal size malleus/incus
and middle ear cavity
Absent EAC
B: CT Rt coronal
D: CT Lft coronal
Click to Return to Algorithm
Squamous Cell Carcinoma involving EAC :
77 year old M with right conductive hearing loss.
A: MR T1 post axial
B: MR T1 post cor
A lobulated, heterogeneously enhancing extracranial tumor is shown arising in the right
infratemporal region (yellow arrows). It extends from the right pinna to the inferior
aspect of the parotid gland and obliterates a portion of the external auditory canal.
Click to Return to Algorithm
Click to Return to Algorithm
Trauma :
42 year old M with left conductive hearing loss s/p trauma with blood in left ear.
*
A: CT Rt axial
C: CT Lft axial
B: CT Rt cor
D: CT Lft cor
Longitudinal fracture of mastoid and petrous portions of the left temporal bone which
also involves the left external auditory canal and middle ear cavity (yellow arrows).
Hemorrhage within the left epitympanum , hypotympanum, left EAC, and mastoid air
cells (red arrows). The left carotid canal is intact (*). Normal Rt side for comparison.
References :
•
Huang BY, Zdanski C, Castillo M.
Pediatric sensorineural hearing loss, part 1: Practical aspects for neuroradiolo
gists. AJNR. 2012 Feb; 33: 211-217.
•
Joshi VM, Navlekar SK, Kishore GR, Reddy KJ, Kumar EC.
CT and MR imaging of
the inner ear and brain in children with congenital sensorineural hearing loss.
Radiographics. 2012 Jun; 32:683-698.
•
Weissman JL. Hearing Loss. Radiology. 1996 Jun; 199: 593-611.
Contact :
Rajesh Gupta MD
[email protected]