Navigating the Temporal Bone and IAC to Reveal Hearing Loss

Pathology: A Diagnostic Algorithm. ASNR 2015

Presentation Number: eEdE-143

Rajesh Gupta MDAmmar Chaudhry MDMargaret Whelan MDLuboslav Woroch DORobert 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)

Anterior

Superior

Facial n

Cochlear n

Superior Vestibular 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

Falciform crest

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

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

m*

e

stfnr

Cor

Axial

*

stapesincus

malleous

EAC#

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

vIAC

bm

moFnl

Cor

Axial

Fnl

L

P

A

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.

B: CT Lft axialA: CT Rt 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

6mm

5 mm

Common Cavity Malformation : 11 month old M with left sensorineural hearing loss.

A: CT Rt axial C: CT Lft axial

B: CT Rt coronal D: CT Lft coronal

Confluence of the cochlea, vestibule, and semicirucular canals forming a common cavity

Common cavity

Widened IAC

Normal Cochlea

Normal: Superior Semicircular canal, Vestibule, and

Basal turn of cochlea

Click to Return to Algorithm

A: MR T1WI Pre-Contrast

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.

Complex cholesterol granuloma : 19 year old M with sudden onset left sensorineural loss, severe vertigo and facial paralysis.

B: MR T2WI

Click to Return to Algorithm

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.

A: MR axial T2 FLAIR B: MR axial T2

C: MR mip axial IAC

Absent Lft IAC

Absent Lft IAC

Normal Rt IAC

Normal Rt IAC

Absent Lft IAC

Click to Return to Algorithm

Otospongiosis : 59 year old F with right mixed hearing loss.

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

No lucency

Otitis Externa : 7 year old F with fever, left ear swelling, tenderness, erythema, discharge and

intermittent left sided conductive hearing loss.

B: CT Lft axialA: CT Rt axial

C: CT Head post contrast axial

Normal Rt external ear canal with small focus of cerumen.

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.

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.

Click to Return to Algorithm

A: CT Rt axial

B: CT Rt cor

C: CT Lft axial

D: CT Lft cor

Normal Scutum

Soft tissue density within the middle ear cavity. It obliterates Prussak’s space and erodes the scutum and ossicles.

Clear Middle ear cavity

External Auditory Canal (EAC) Atresia : 14 year old M with right conductive hearing loss.

A: CT Rt axial C: CT Lft axial

B: CT Rt coronal D: CT Lft coronal

Absent EAC

Absent EAC

Small malleus and middle ear cavity

Normal EAC

Normal size malleus/incus and middle ear cavity

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

Trauma : 42 year old M with left conductive hearing loss s/p trauma with blood in left ear.

A: CT Rt axial

B: CT Rt cor

C: CT Lft axial

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.

*

Click to Return to Algorithm

References :

• Huang BY, Zdanski C, Castillo M. Pediatric sensorineural hearing loss, part 1: Practical aspects for neuroradiologists. 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 MDrajesh.gupta@stonybrookmedicine.edu