Download MR IMAGING OF INNER EAR Sarbesh Tiwari

MR IMAGING IN INNER EAR
PATHOLOGY
ModeratorPROF & HOD . DR R.K. GOGOI
Presented by :: Sarbesh Tiwari
Introduction
The ear functions both as an organ of hearing and as an organ of equilibrium
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Embryology of ear
• The ear is the first organ of special senses to
become differentiated in man, inner ear reaches
full adult size by midterm
• The external and middle ear develop from 1st
and 2nd brachial arch
• Neural sound perceiving apparatus of inner ear
develops from ectodermal otocyst
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External Ear
PINNA (auricle) :
# sixth week of embryonic life,
# six tubercles appear around 1st
branchial cleft.
# They progressively coalesce to form
the auricle
External auditory meatus
# develops from the first branchial
cleft.
# 16th embryonic week,
# cells proliferate and form a meatal
plug.
# Recanalisation of this plug forms the
epithelial lining of the bony meatus.
# External ear canal is fully formed by
the 28th week of gestation
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MIDDLE EAR
• Tympanic membrane: Develops from all
the three germinal layers. Outer epithelial
layer by ectoderm, Middle fibrous layer by
mesoderm & Inner mucosal layer by
endoderm.
• Middle ear cavity :
# Develops from endoderm of
tubotympanic recess which arises from 1st
and partially from 2nd pharyngeal pouches.
# Head of Malleus and short process of
incus are derived from mesoderm of 1st
arch
# Rest of malleus and incus with stapes
suprastructure develop from 2nd arch
# footplate and annular ligament which are
derived from the otic capsule
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Inner ear
• Starts by 3rd week of fetal life and completed by 16th wks
• The inner ear is derived from the ectoderm in the
region of the hindbrain.
• A thickening of the ectoderm, the otic placode
becomes invaginated to form the auditory/otic vesicle.
OTIC PLACODE
OTIC PIT
OTIC VESICLE
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DIFFERENTIATION OF OTIC VESICLE INTO INNER EAR ELEMENTS
• Each vesicle divides into
-- the dorsal portion which forms the utricle, semicircular
canals and endolymphatic duct, and
-- the ventral component, which gives rise to the saccule and the
cochlear duct (scala media).
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• Mesoderm around otocyst soon forms a cartilaginous otic
capsule.
• Part of the cartilaginous shell undergoes vacuolization, and
two perilymphatic spaces (scala vestibuli and scala tympani)
are formed.
• Ossifies by 25 weeks
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• Small group of cells breaks away otic capsule and
along with cells of neural creast origin forms the
statoacoustic ganglion.
• The ganglion subsequently splits into vestibular and
cochlear nerves.
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Anatomy of inner ear
• It lies in the petrous part of the temporal bone
• Inner ear consists of osseous labyrinth that encloses
membranous labyrinth.
Outer bony labyrinth
1. bony cochlea
2. vestibule
3. three bony semicircular
canals
4. Vestibular and cochlear
aqueduct
Inner membranous
labyrinth
1. Cochlear duct
2. Utricle
3. Saccule
4. Three membranous
semicircular canals
5. Endolymphatic system
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Bony labyrinth
1. Vestibule :- Central rounded portion of labyrinth.
•
•
Medial wall has two recesses, a spherical recess for saccule
and an elliptical recess for utricle.
Continues antero-inferiorly with cochlea and posteriorly
with SCC & vestibular aqueduct.
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2. Semicircular Canal:
• They are three in number, the
lateral, posterior and superior,
and lie in planes at right angles
to one another.
3. Cochlea :The bony cochlea is a coiled
tube making 2.5 to 2.75 turns
round a central pyramid of bone
called the modiolus.
The bony cochlea contains three
compartments:
(a) scala vestibuli,
(b) scala tympani,
(c) scala media or the
membranous cochlea
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4. Vestibular aqueduct
• Tubular structure that arises from
vestibule and runs along posterior
inferior aspect of petrous bone
• Contains endolymphatic duct and
sac
• Normally measures less than
1.5mm in diameter or
approximates the size of post. SCC
which runs anterior and parallel
the aqueduct.
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Membranous labyrinth
• Cochlear duct : Also called the scala media. It is a blind
coiled tube. It appears triangular on cross-section and its
three walls are formed by:
(a) the basilar membrane,
which supports the organ of
corti,
(b) the Reissner's membrane
which separates it from the
scala vestibuli,
(c) the stria vascularis, which
contains vascular epithelium
and is concerned with
secretion of endolymph.
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Utricle and saccule
The utricle lies in the posterior part of bony vestibule. It receives
five openings of the three semicircular ducts
The saccule anterior to the utricle and opposite the stapes
footplate
Endolymphatic duct and sac
• Endolymphatic duct is formed by
the union of two ducts, one each
from the saccule and the utricle.
• It passes through the vestibular
aqueduct.
• Its terminal part is dilated to
form endolymphatic sac which
lies between the two layers of
dura on the posterior surface of
the petrous bone
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Internal Auditory Canal
• A bony conduit that transmits VII & VIII cranial
nerves from pontomedullary junction to inner ear.
Divided by a bony lamina
(falciform crest) into
A. Smaller superior part
• Superior vestibular N.
• Facial Nerve
B. Larger Inferior part
• Inferior vestibular N.
• Cochlear nerve.
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Blood supply of labyrinth
• Arterial supply : Labyrinthine artery which is a
branch of anterior-inferior cerebellar artery
• Venous drainage : through three veins :
internal auditory vein
vein of cochlear aqueduct
vein of vestibular aqueduct
Inferior petrosal sinus
Transverse sinus.
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Cross sectional anatomy of inner ear
Fig.1.-----Axial HRCT of Inner Ear
White arrowhead : Modiolus with cochlea
White arrow : I A C
Black arrowhead : Vestibule
Black arrow : Posterior semicircular canal18
Cross sectional anatomy of inner ear
Fig. 2– Axial heavily T2 WI
Axial images shows basal turn of cochlea
and osseous spiral lamina
Fig. 3– Axial heavily T2 WI
Middle and apical turns with the modiolus
(arrowhead) and the spiral lamina (curved
arrow) dividing the cochlea into scala
vestibuli and scala tympani . The nerves
are seen in CP angle.
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Cross sectional anatomy of inner ear
Fig. 3– Sagittal T2 MR Images
Showing the four nerves within IAC : The facial nerve (arrow head), cochlear nerve
(curved arrow) and superior and inferior vestibular nerves (arrowhead)
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When and why MRI
• MRI essentially compliments CT because of its
excellent soft tissue contrast
• MRI is directed toward imaging of
# Fluid containing spaces in temporal bone
# Vascular structure and their pathologies
# Adjacent brain parenchyma
# Evaluation of 7th and 8th nerve complex
• Loosely, one can state that conductive hearing loss is
mainly evaluated by CT scan and sensorineural
hearing loss by MRI
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IMAGING PROTOCOL -- MRI
Inner ear Imaging
• 1.5 or 3 Tesla MRI is preferred
• Sedation used in most children •
• 3D volumetric CISS in axial plane
with coronal and sagittal
•
reformation and MIP
reconstruction
• Slice thickness of 0.4 – 0.7 mm •
• Oblique sagittal reformatted
images in plane perpendicular to
7th and 8th nerve in IAC
• Routine axial T2WI of brain to
exclude CNS causes of
sensorineural hearing loss
• 3D MPRAGE may be added.
Tumors and infection
Precontrast brain with thin section
through the CPA- IAC region
MRA/ MRV as required
Post contrast fat sat.
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3D CISS
• Three dimensional (3D) constructive interference in
steady state (CISS) is a heavily T2 weighted fully refocused
gradient echo MR sequence.
• Being heavily T2 weighted it is better suited for imaging of
structures surrounded by fluid like 7th – 8th nerve complex
and membranous labyrinth.
• 3D sequence , so reconstruction in any plane possible.
• Other uses:1. Evaluation of cranial nerves
2. Diagnosis of NCC
3. Evaluation of CSF rhinorrhea
4. Evaluation of ventricular system etc.
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The 3 D reconstruction of inner ear done with post-processing by maximum
intensity projection(MIP) and multi-planar reconstruction(MPR) by using 3DCISS sequence
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Congenital malformation of inner ear
Cochlear abnormalities are numerous and Jackler et al classified them on the basis
of arrested development during organogenesis
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TIMELINE OF CONGENITAL MALFORMATION
OF INNER EAR
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COMPLETE LABYRINTHINE APLASIA OR MICHELE
APLASIA
• Most severe inner ear deformity
• Etiology : Arrested development of otic placode during 3rd
gestational week
• Extremely rare – only 1% of inner ear malformation.
• Unilateral/ bilateral. Unilateral cases are associated with
contralateral inner ear dysplasia.
HRCT :# Complete absence of inner ear with hypoplasia of petrous
bone and narrow atretic IAC.
# Absence of round and oval window
# Flattening of medial wall of middle ear cavity
MRI : 8th cranial nerve not visualized on MR images
Associated with skull base, CVJ and vascular anomalies 28
Axial CT : Flat middle ear cavity and
hypoplastic petrous bone
Coronal CT : Atretic internal auditory
canal
Sagittal MRI : single nerve within the
IAC, suggesting absent 8th nerve
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Common cavity
• Defined by absence of normal differentiation between
the cochlea and vestibule
• 25% of cochlear malformation
• Arrest during 4th arrest of gestation
• Associated with poor
differentiation of membranous
labyrinth as well resulting in
severe to profound hearing loss
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Confluence of cochlea and vestibule in a
cystic cavity with no internal architecture
Common cavity
Absence of cochlear nerve
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Cochlear Aplasia
• Cochlea fails to form
• Due to arrested development in latter part of 5th week
• The vestibule and semicircular canal are often
malformed but may be normal.
Imaging features :
1. Absence of cochlea
2. Dilatation of vestibule
3. Deformity of semicircular
canal
4. dense otic bone is present
where cochlea would be
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Axial CT images shows dilated globose
vestibule (arrow head) , dense sclerotic bone
where cochlea should be (curved arrow) ,
and a stunted dilated posterior semicircular
canal (straight arrow).
Coronal CT images shows malformed
dilated lateral semicircular canal (straight
arrow) with stunted superior semicircular
canal (curved arrow)
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Cochlear Hypoplasia
• Small rudimentary cochlear bud with normal or
malformed vestibule and semicircular canal
• 6th week of gestation -- 15 % of incidence
• CT scan:
# Height around the cochlea is around (3-6) mm as
compared to normal height of 12-13 mm
# Abnormal Small IAC
# Though cochlea is visible it has
one turn or partial turn
Diagram shows : Small cochlear bud and
abnormally small and deformed vestibule
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Axial CT & MRI :- Small cochlear bud and abnormally small and deformed vestibule
Stenotic IAC
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Incomplete partition or dilatation defect
• Due to development around 7th week
• Includes the Mondini’s defect (most common malformation –
50%)
• Here basal turn of the cochlea is formed , however the middle
and apical turns are replaced by a common cavity.
• Imaging : (Triad of )
# Instead of 2.5 turns , only 1.5 turns are present
# enlarged vestibule with normal semicircular canal
# enlarged vestibular aqueduct containing a
dilated endolymphatic sac.
• MRI reveals : complete or partial absence of the normal
interscalar septum
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Axial CT shows absence of
the modiolus with a cystic
cochlear apex (straight
arrow) , dilatation of
vestibular aqueduct
(arrowhead) and vestibule
(curved arrow)
Slightly lower level shows normal
basal turn
Coronal CT images shows the cystic cochlear apex
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Lateral semicircular canal malformation
• Of anomalies of SCC, lateral semicircular canal malformations
is most frequent.
• Hypoplasia of semicircular canal can lead to compensatory
enlargement of the vestibule (lateral semicircular canalvestibule dysplasia syndrome)
• Aplasia of SCC is associated with CHARGE syndrome
Axial CT shows a stenotic IAC (curved
arrow) , mildly dilated vestibule with
stunted lateral semicircular canal ( straight
arrow). The posterior semicircular canal
appears normal.
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Large vestibular aqueduct syndrome
• The large vestibular aqueduct syndrome (LVAS) refers to
the presence of congenital sensorineural hearing loss
with an enlarged vestibular aqueduct
• C/F : Sensorineural hearing loss starts in childhood and is
progressive
• Associated with Pendred syndrome, vestibular and
cochlear anomalies
• Imaging :
# Vestibular aqueduct of ≈ 1.5 mm is considered the
upper limit of normal .
# Usually less than posterior semicircular canal.
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IAC and cochlear nerve anomalies
• IAC normal diameter range from 2- 8 mm, average 4mm
• Diameter less than 2mm, described as Stenotic
• Sagittal oblique images obtained in a plane perpendicular
to the long axis of IAC provides best depiction of the four
major nerves of IAC
• Types of cochlear anomalies
Type I – A Stenotic IAC with absent 8th nerve
Type 2 – A common vestibulocochlear nerve with
hypoplasia or aplasia of cochlear branch
2a – associated with other inner ear anomaly
2b – No associations.
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Aberrant (intratympanic) Internal Carotid Artery
• Due to abnormal regression of cervical ICA during
embryogenesis
• Aberrant ICA has a sharp angled posterolateral course
where it tracks through the middle ear over the
cochlear promontory.
Importance :
# Produces pulsatile tinnitus in few pt.
# May be confused with Glomus tympanicum
Paraganglioma
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CT:
1. Posterior carotid plate is absent
2. Horizontal part of carotid canal
appears to merge with lateral
cochlear promontory
MRI :
1. Routine MR sequence are not
helpful.
2. MRA shows unusual
posterolateral course of ICA
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• Other arterial anomalies :
 1. Persistant stapedial artery
 2. Persistant trigeminal Artery
 3. Anomalous artery in the stria vascularis of the
cochlea
 Ectatic vascular loops of AICA/PICA or tortous course
of vertebral artery may present with tinnitus due to
compression of VIII nerve complex.
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Venous variants
1. High riding Jugular bulb : Large jugular bulb reaching
above the internal auditory canal with intact sigmoid
plate
2. Dehiscent Jugular Bulb : The sigmoid plate is
deficient, the bulb protrudes into the middle ear
cavity. It is a common cause of a retro-tympanic
vascular mass.
3. Jugular bulb diverticulum
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Dehiscent jugular bulb
High riding jugular bulb
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LABYRINTHITIS
Inflammation of membranous
labyrinth.
Viruses are the most common
etiologic agents, but can be
bacterial or autoimmune .
Types:
1. Tympanic labyrinthitis : Infection spreads from middle ear
via oval or round window or labyrinthine fistula
2. Meningogenic : Infection spreads along CSF spaces via IAC
or cochlear aqueduct. Usually bilateral.
3. Hematogenic labyrinthitis : spread of infection by bloodstream. Virus e.g, measles and mumps, syphilis etc
4. Post traumatic labyrinthitis.
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Imaging features:
CT : # Usually normal in acute stage
# Ossification of membranous labyrinth in late chronic
phase
MRI : contrast enhanced MR is the method of choice
# T1- CEMR shows moderate to intense enhancement
within normal fluid filled structure of inner ear
# Usually viral conditions causes subtle enhancement
and bacterial causes intense enhancement.
Complication : Labyrinthitis ossificans is a Sequela of
chronic labyrinthitis, usually Pyogenic in origin.
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Axial MRI in patient with suppurative
labyrinthitis. Enhancement of internal
auditory canal, cochlea, and
vestibule.
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Labyrinthitis ossificans
• Labyrinthitis ossificans (LO) is the pathologic formation
of new bone within the lumen of the otic capsule.
Etiology :1. Sequela of inflammation of the inner ear, e.g bacterial
meningitis or purulent labyrinthitis
2. Vascular obstruction of the labyrinthine artery
3. Autoimmune labyrinthitis etc.
Imaging :
CT scan :- Osseous deposition within the membranous
labyrinth
MR Imaging :- Loss of the normal high signal on T2weighted images from displacement of the
endolymphatic fluid is suggestive of this diagnosis.
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CHOLESTEATOMA WITH COMPLICATION
MRI features of cholesteatoma ::-Hypointense on T1WI & Hyperintense on T2 WI
No enhancement or faint peripheral rim
enhancement
Delayed Contrast scan (after 45min) – continued
enhancement of inflammatory or granulation tissue
and not in cholesteatoma.
DWI – Cholesteatoma shows restricted diffusion and
are hyperintense on b= 1000/m2.
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CHOLESTEATOMA WITH COMPLICATION
A . Labyrinthine fistula -- Most frequent complication with
middle ear cholesteatoma (prevalence of 5%– 10%).
• C/F : Episodic vertigo, sensorineural hearing loss, tinnitus
• CT Findings :1. Dehiscent lateral semicircular canal support the
diagnosis
2. Uncommonly , dehiscence of cochlear promontory or
fistula in oval window.
• MRI Findings :- a labyrinthine fistula causing labyrinthitis,
shows enhancement of the membranous labyrinth.
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Other complications B. Perineural extension of cholesteatoma along facial
nerve.
C. Erosion of the sigmoid sinus plate and consecutive
thrombosis, tympanic tegmen erosion and
subsequent intracranial invasion, recurrent\bacterial
meningitis, and intracranial abscess are rare
complications, which, nevertheless, require an
urgent CT/MR imaging examination
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Petrous apex granuloma
• Cholesterol granuloma is an inflammatory granulation
appearing in response to the deposits of cholesterol crystals
• Etiology: Middle ear disorders causing mucosal edema and
deposition of cholesterol crystal
• Site : Middle ear cavity followed by mastoid process and
petrous apex
• C/F : Hearing loss, vertigo, headaches, tinnitus
Any focal neurological deficit, especially of cranial
nerves V–VIII
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Petrous apicitis
• Petrous apicitis is infection with involvement of bone at
the very apex of the petrous temporal bone.
• Pathology : Osteitis developing from infected and
obstructed air cells in a pneumatised petrous apex
• C/F: Presents with Gradenigo’s syndrome
1. petrous apicitis, with
2. 6th nerve palsy, and
3. Retro-orbital pain, or pain in the cutaneous distribution
of the trigeminal nerve, due to extension of inflammation
into Meckel's cave.
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CT scan :
1. Erosive lysis with ill-defined
irregular edges of petrous apex
2. Peripheral enhancement of
petrous apex with dural
enhancement and thickening
MRI:
1. Fluid signal intensity in petrous
apex often with peripheral
enhancement
2. More sensitive in detecting dural
thickening and enhancement as
well as leptomeningitis,
cerebritis and cerebral abscess
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BELL’S PALSY
• Bell's palsy is characterized by rapid onset lower motor neuron
facial nerve paralysis, often with resolution in 6 - 8 weeks.
• Etiology :
1. Idiopathic
2. Reactivation of Herpes Simplex Virus infection in
geniculate ganglion.
• Pathogenesis : Secondary to swelling and edema of the 7th
nerve within the facial nerve canal
• Indication for imaging : MRI not done routinely . Indicated if :# Decompressive surgery is being planned
# Atypical: No recovery in 6 wks, recurrent palsy,
multiple cranial nerve involvement.
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•On MRI imaging enhancement of the facial nerve within the
tympanic portion of the facial nerve canal supports the
diagnosis.
•Reported enhancement rates vary from 57% to 100%.
•Typically long segments of the facial nerve enhance in a
uniformly linear fashion
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Facial Schwannomas
Facial nerve Schwannoma are uncommon tumors arising from
the Schwann cell sheath
Site : Geniculate ganglion, followed by labyrinthine and
tympanic segment.
Pathology : Originate from surface of the nerve, and splay the
nerve fibres over their eccentric growth
C/F : 1. Persistent and gradually facial paresis.
2. Conductive hearing if tympanic segment involved
causing ossicular compression
3. In CP angle or IAC : Presents with sensorineural
deafness with facial paresis being rare in these cases.
4. Other like, tinnitus, hemifacial spasm, and otalgia 69
Imaging features
HRCT :
Enhancing soft tissue density lesion along facial nerve
Intracanalicular or CP angle tumor can cause bony erosion
of anterosuperior portion of IAC
MRI:
T1 : Iso- to hypo intense relative to gray matter
T2 : Hyperintense ; large lesion may show heterogeneous
signal
T1 C+ (GAD) : Homogeneous enhancement with larger
lesions showing cystic degeneration as focal
intramural low signal intensity
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CT SCAN : focal enlargement of the
labyrinthine segment of the facial nerve
MRI: homogeneously enhancing mass
filling the internal auditory canal with
extension into the CP angle and
labyrinthine segment
Diagnosis : Facial Nerve Schwannoma
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The axial T1-weighted post-contrast MR image (left) shows homogeneous
enhancement of the mass (between arrows).
The bone algorithm CT (right)at the same level shows focal enlargement
of the descending segment with extension toward the external auditory
canal.
Diagnosis : Schwannoma of the mastoid segment of facial nerve.
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FACIAL NERVE HEMANGIOMA
• Rare tumor of vascular origin (0.7% of all intra-temporal
tumors)
• This along with other vascular malformations are termed
as Intra-temporal Benign Vascular Lesions
Age : 3rd to 6th decade without sex predilection
Site : Geniculate fossa followed by IAC
C/F: Facial nerve paralysis progressing over weeks.
Sensorineural hearing loss and pulsatile tinnitus may
occur if there is erosion of otic capsule.
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IMAGING FINDINGS
MRI :
# Intratemporal hemangiomas characteristically have
 variable signal intensity on T1-weighted images
 increased signal intensity on T2-weighted images
 avid contrast enhancement.
# Low-signal-intensity foci may be seen on T1- and T2-weighted
images, corresponding to the ossific matrix of the lesion
CT Scan : Enables exquisite visualization of associated bone
changes
Tumor causes erosion which are irregular with indistinct
margins giving a “Honeycomb” pattern of eroded bone.
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Anatomy: Cerebellopontine angle
• CRANIAL NERVE V , VII & VIII
• ARTERIES :
SUP. CEREBELLAR A.
AICA
• VEINS :
TRIBUTARIES OF
SUP PETROSAL V.
Boundaries :- Anterolateral surface of pons & Cerebellum
- Posterior surface of petrous temporal bone
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Imaging signs of extra-axial CPA cistern
masses
1. Enlarged ipsilateral CPA cistern
2. CSF/ Vascular “ Cleft” between mass and
cerebellum
3. Displaced gray-white interface around mass
4. Brainstem rotated
5. Fourth ventricle compressed.
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Cerebellopontine angle cistern masses
Common tumor
• Acoustic Schwannoma
[75%]
• Meningioma [10%]
• Epidermoid [5%]
• Non acoustic
Schwannoma [4%]
• Aneurysm
• Metastasis
• Paraganglioma
• Ependymoma
• Choroid plexus papilloma
Uncommon tumor
•
•
•
•
•
Arachnoid cyst
Lipoma
Dermoid
Brain stem glioma
Osteo-cartilagenous
tumor
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Vestibular Schwannoma
• Benign tumor arising from Schwann cells
that wrap vestibulocochlear nerve
• 70- 80 % of CPA lesions
• Age – 5th -6th decade.
• B/L acoustic Schwannoma pathognomonic for NF-2.
• Origin : Most from Inferior Vestibular Nerve, at glialschwann cell interface
• Morphology :
# Entirely intracanalicular
# Intracanalicular with cisternal component ‘ Icecream cone appearance’.
# Rarely purely intracisternal.
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• Pathology : Compact Antoni Type A tissue
or loose textured , often cystic Antoni type
B tissue
• C/F : SNHL or tinnitus, Hydrocephalus, CN
palsies (If large)
• Imaging findings : CT SCAN:# NECT :- Extra axial hypodense to isodense
mass with its base on post aspect of petrous
temp in region of IAM.
# CECT :- Marked enhancement, large lesion
m/b heterogeneous.
# Erosion & widening of Internal Acoustic
canal.
# Small lesions c/b missed d/t beam
hardening artifact.
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MR IMAGING FEATURES
• T1WI: 2/3rd are hypointense and 1/3rd are isointense.
may contain hypo intense cystic areas
• T2WI :
# Heterogeneously hyperintense
# Small leson : "Filling defect" in high signal CSF of CPA-lAC cistern
# may have associated peri-tumoural Arachnoid cysts
• T1 C+ (Gd) :
# contrast enhancement is vivid
# Heterogeneous in larger tumors
# Occasionally, may show extension into the cochlea and dural tail
of enhancement.
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MENINGIOMA
• Extra-axial neoplastic lesions arising from
Arachnoid cap cells.
• 2nd most common CPA tumor (10%)
• Site : arises from the meninges covering posterior petrous bone.
• Female > Male (2-3:1) , peak age = 60yrs.
• C/F : Small Meningioma -entirely asymptomatic
Large tumors – headache, paresis or neurological deficit.
• Morphology :
# "Mushroom cap" (hemispherical) with broad base towards
posterior petrous wall (75%)
# Plaque-like : +/- bone invasion with hyperostosis (20%)
# Ovoid mass : mimicking Acoustic Schwannoma
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Imaging features
NECT :
# Frequently hyperdense with focal areas of calcification
# Bony hyperostosis of petrous bone
CECT : Presence of broad dural base with dural tail and intense
enhancement is typical.
MRI :
# Isointense to brain parenchyma in T1 & T2WI
# Blooming s/o calcification in GRE
# Dural tail with other features of extra-axial lesion
# May rarely extends into IAC and presents with diagnostic
dilemma.
ANGIOGRAPHY : Homogenous blush which lasts till late venous
phase (Mother In Law sign)
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Lipoma of internal auditory canal
 Rare congenital lesion often associated with
CP angle lipoma.
 CT Scan: Fat attenuating non enhancing lesion
 Presents with unilateral sensorineural hearing
loss
 MRI : Non enhancing lesion which is
hyperintense on T1WI & T2WI with
suppression of SI on fat saturated images.
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GLOMUS TUMOR (PARAGANGLIOMA)
• Slow growing, locally aggressive vascular
tumor arising from chemoreceptor cells
• Arising from the 9th & 10th nerve,
 most common tumor of middle ear
 2nd most common tumor of temporal
bone
Unique names associated with location: Jugular bulb – Glomus jugulare
Middle ear -- Glomus tympanicum
Carotid body – Carotid body tumor
Vagus nerve ganglion-- Glomus vagale
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• Clinical feature:
 Pulsating tinnitus with conductive hearing loss
 Invasion into cochlea leads to sensorineural hearing loss
 Otoscopy : Tympanic membrane appears blue
: Isolated to middle ear
cavity
 Soft tissue density protruding from
cochlear promontory .
 Homogenous enhancement on post
contrast scan.
Confined to jugular fossa and large at
presentation
Invades the hypo-tympanum and
infralabryrinth compartment
Tumor can follow the Jugular venous system
upto lower cervical jugular vein.
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MRI features :
T1WI – Low signal intensity
T2WI – High signal Intensity
T1C+ -- Marked intense enhancement
Salt – pepper appearance (T1 + T2) : Salt represents areas of
hemorrhages and pepper represents areas of flow void.
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Perineural Spread of tumors
• Common with head & neck cancer.
• Nasopharyngeal CA followed by adenoid cystic carcinoma
and lymphoma.
• Trigeminal and facial nerve are the commonest nerves
involvement.
Features of Perineural spread :1. Enlargement and enhancement along the course of nerve
2. Obliteration of the fat surrounding neural foramina
3. Denervated muscles becomes atrophic with time and
replaced with fat.
4. Tumor in lateral aspect of pons should raise a suspicion.
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Endolymphatic hydrops ( Meniere’s )
• Refers to increased hydraulic pressure within inner ear
endolymphatic system.
• Etiology:
# Idiopathic (Meniere’s disease)
# Association with autoimmune disease , hormonal
and metabolic condition noted (Meniere’s syndrome)
• C/F : 1. Fluctuating hearing loss
2. Episodic vertigo
3. Tinnitus
4. Aural fullness
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Role of MRI in Meniere’s disease
• Bilateral intratympanic GBCA is being used for semi quantitative
evaluation of Meniere’s.
• 1- 1.5 ml of diluted gadolinium is injected into middle ear through
a small myringotomy and evaluated after 24 hours.
• 3D FLAIR is used to evaluate inner ear
• 3Tesla is better.
• The gadolinium successfully penetrated the round window
membrane, entering the perilymphatic space and delineating the
contrast-enhanced perilymphatic and contrast-negative
endolymphatic spaces of the inner ear
• If the non-enhancing endolymphatic area exceed the perilymphatic
area, it is considered significant.
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Normal : Inner ear ; No hydrops
3D FLAIR : Significant enlargement
[33–50%] of the endolymphatic
compartment in the cochlea;
in the vestibule and semicircular
canal endolymphatic hydrops [>50%]
has displaced almost all perilymph.
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Endolymphatic sac tumor
• Papillary adenomatous tumors
originating form endolymphatic sac.
Described by Heffner in 1989.
• Occurs sporadically or with VHL disease
• Age : Presents early if associated with
VHL
• C/F : Sensorineural hearing loss +
Tinnitus +Vertigo
Imaging : CECT
a. Heterogeneous lesion with “motheaten” retrolabyrinth petrous bone
b. Intratumoral spiculated bone seen
c. Intense enhancement in seen
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MRI Features :
 T1 /T2WI : Mixed signal intensity lesion
where focal high signal intensity d/t
subacute hemorrhage and low signal
intensity d/t calcification or hemosiderin.
 Blood filled cysts and protein cyst, both
appearing hyperintense on T1/T2WI suggests
the diagnosis
 Masses larger than 2 cm shows flow voids
 T1C+ : Heterogeneous enhancement
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ISSUES WITH POST COCHLEAR IMPLANT CASES
 Cochlear implants are not safe at 1.5T
 MR compatible CI are now available
 External component should be removed in all cases
 Role of MRI is in preimplant evaluation to exclude
cochlear aplasia which is contraindication for
surgery. Absent Cochlear nerve is relative
contraindication.
 CT scan is better for post-operative evaluation of
these patients.
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Conclusion
MR provides accurate anatomical delineation of
complex soft tissue of inner ear
3D reconstruction improves preimplant
evaluation
Detailed delineation of 7th & 8th nerve complex in
temporal bone as well as membranous labyrinth
Depiction of tumor size and extension into CP
angle determines the approach to surgical
removal.
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References
1. Diagnostic Radiology- Neuroradiology – AIIMS – MAMC- PGI
Course series . 3rd edition.
2. CT and MRI of whole body – John R Haaga 5th edition
3. Joshi VM, Navlekar SK et.al -Ct and MRI imaging of the inner
ear and brain in children with sensorineural hearing loss.
Radiographics. 2012 May-Jun;32(3):683-98
4. Jeremy Hornibrook, Mark Coates, Tony Goh, Philip Bird et.al
MRI imaging of the inner ear for Meniere’s disease. Journal of
the New Zealand Medical Association. 27 August 2010, Vol
123 No 1321
5.
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