Ear is the part of auditory system. It not only receives sound, but also aids in balance and body position.The external ear consists of auricle and the external auditory canal. The ext auditory canal is 2.4 cm in length in adult. The middle ear lies between the ext and inner ear and contains the ossicles and muscles for sound conduction.Inner ear
The cochlea is developed sufficiently by 20 weeks of gestation and foetus can hear in the womb of the mother. This probably explains how Abhimanyu, while still unborn, could have heard the conversation between his mother and father (Arjuna) in the legend given in the Grear Indian epic of Mahabharata written thousands of years ago.
Utricular portion3 diverticula for semicircular canalsSaccular portionTubular diverticulum (cochlear duct) grows in spiral fashion to become membranous cochleaThe organ of Corti differentiates from cells along the wall of the cochlear duct.
Development of cochlea is complete by 8th weekVestibule by 11th weekSemicircular canal by 19- 22 wks
The oval window of the vestibule is the interface between the mechanical and neural element of the ear. It is covered by the annular ligament, which surrounds the footplate of the stapes.The round window is bony opening in the basal turn of cochlea covered by fibrous membrance.
Each canal has an ampullated end which opens independently into the vestibule and a nonampullated end. The non-ampullated ends of posterior andsuperior canals unite to form a common channel called the crus commune.
MAGNETIZATION-PREPARED RAPID ACQUISITION WITH GRADIENT ECHO.
A steady state sequence is a type of gradient echo sequence in which residual transverse magnetization is refocused so that a steady magnitude longitudinal and transverse magnetization is achieved after a few repetition times (TR) periods.The same sequence in GE machine is called 3D FIESTA. Philips called DRIVE
Inner ear abnormalities affects the cochlea, semicircular canals, vestibule and the vestibular/ cochlear aqueducts.
coloboma, heart anomalies, choanalatresia, retardation of growth and development, and genital and ear anomalies
An enlarged vestibular aqueduct is defined by an anterior-posterior diameter greater than 1.5 mm, at the midpoint between its external aperture and the common crus. Hearing loss usually is bilateral, progressive in nature, and may be associated with vertigo. Some cases may be familial.
Difference with paraganglioma is essential because a biopsy in leiu of a malignancy may have a disastrous consequences.
Others arterial abnormality are :
Labyrinthitis ossificans (LO) is the pathologic ossification of spaces within the lumen of the bony labyrinth and cochlea that occurs in response to a destructive or inflammatory process. Regardless of the etiology, the most common region of cochlear ossification is the scala tympani of the basal turn, with the most extensive disease noted in post-meningitic cases.
Axial CT scan reveals at the level of internal auditory canal reveals – complete ossification of the vestibule and semicircular canal.
Magnetic resonance imaging (MRI) findings. (A) T2-weighted images revealed cholesteatoma induced inflammation in the right middle ear with abnormal communication with inner ear fluid-filled space. (B) Routine T1 weighted images after intravenous gadolinium administration revealed areas showed pathological enhancement in the lateral canal and cochlea on the right side. (C) High-resolution T1 weighted scans demonstrate prominent enhancement of lateral canal and entire length of cochlea more clearly (Cochlea, indicatedby arrow-heads; lateral semicircular canal, arrows)
Cholesterol granuloma may occur within any area of pneumautized temporal bone and it is associated with a variety of middle ear disorders followed by chronic obstruction of air exchange and inadequate aeration. Subsequently, absorption of gases, hypoxia, or negative pressure may cause mucosal edema with resultant stagnation and extravasation of blood, which can produce hemosiderin and cholesterol crystals. These substances lead to foreign-body reaction. Thus, cholesterol granuloma develops itself by repeating this process
A CT of a cholesterol granuloma is nonenhancing, well marginated, and bone erosion is usually present(21). The MRI of a cholesterol granuloma is pathognomonic – there is highsignal intensity on both T1 and T2-weighted images and there is no gadolinium enhancement, whereas cholesteatomas and epidermoid cysts show slightly greater cerebrospinal fluid signal intensity
The facial nerve is the nerve of facial expression. It arises from lower border of pons at the pontomedullary junction from three different nucleus.Motor nucleus which hooks around the 6th nerve nucleus.Nucleus tractussolitarius : supplies taste sensation to tongueSuperior salivatory nucleus : Parasympathetic innerveation to salivary glands.The facial nerve is described as having six divisions: 1. Cisternal 2. Intracanalicular 3. Labyrinthine 4. Tympanic 5. mastoid and 6. Extratemporal segment.
Within the CP angle, the facial nerve is the most anterior and the vestibulocochlear nerve is the most posterior, with the nervusintermedius between the two.
The facial nerve enters the internal ear through the fallopian canal and this segment is callled the labyrinthine segment. At geniculate ganglion, it takes an acute turn posteriorly to form the tympanic portion of the nerve.The nerve than turn at 90 degrees to form the mastoid segment and exit the ear at the stylomastoid foramen.
Subtle but definite (asymetrical) enhancement of the left VIIth nerve especially at the genu and in the horizontal portion of the nerve. This indicates an inflammatory process rather than Schwannoma as the enhancement is diffuse rather than focal, and non mass like.
, there is abnormal globular signal hyperintensity in the region of the labyrinthine segment of the facial nerve and the inferior aspect of the left geniculate fossa (arrow), with stippled punctate foci of hypointense signal. In b, there is contiguous abnormal signal intensity in the more craniad aspect of the geniculate fossa intense enhancement of the lesion (arrow), with the exception of a few punctate areas of nonenhancement that correspond to the stippled hypointense foci IThere is a mildly expansile lytic lesion with fine internal high-attenuation spiculations in the region of the geniculate ganglion (long arrow). There is involvement of the labyrinthine portion of the facial nerve canal (short arrow) and proximal tympanic segment (*). (b)Coronal targeted reformatted CT image of the left temporal bone at the level of the cochlea (1-mm section thickness). The image is centered on the expansile le-sion shown in a(arrow) and best demonstrates the honeycomb pattern of internal bone spicules within the geniculate fossa
Corresponding drawing depicts a mass emanating from the internal auditory canal, bulging into CPA and impinging upon the middle cerebellar peduncle.
Trigeminalscnwannoma is the most common non-acoustic schwannoma.
Second most common extra-axial neoplasm in adults
Asymmetry of the internal auditory canals of more than 2 mm suggests the presence of mass.
Axial T1-weighted MRI image demonstrates a mass isointense to cerebral cortex involving the left cerebellopontine angle. B. Axial T2-weighted MRI image at the same level shows the mass is intermediate high-signal-intensity (higher then cerebral cortex but less than CSF). There is mass effect on the 4th ventricle and the pons without edema.Post-gadolinium MRI images show avid, homogeneous enhancement of the mass. There is a small dural tail (black arrow) and extension into the left IAC via the porusacousticus (white arrow). The IAC is not dilated. Mass effect is again seen on the pons, middle cerebellar peduncle, and 4th ventricle.
Axial T1-weighted image (400/14/2) shows a hyperintense mass in the right vestibule (arrow).B, Axial T2-weighted fast spin-echo image (4000/102/4) shows the intravestibular mass to be hypointense relative to the fluid-filled membranous labyrinth (arrow).C, Coronal T2-weighted fast spin-echo image (4000/102/4) shows the intravestibular mass (large arrow), the horizontal semicircular canal (small arrow), and the basal turn of the cochlea (open arrow).D, Axial T1-weighted image (500/20/4) with fat saturation reveals saturation of the intravestibular mass (arrow), consistent with a lipoma.
Ménière disease is idiopathic by definition, whereas Ménière syndrome can occur secondary to various processes interfering with normal production or resorption of endolymph (eg, endocrine abnormalities, trauma, electrolyte imbalance, autoimmune dysfunction, medications, parasitic infections, hyperlipidemia).
gadolinium-based contrast agent (GBCA)
CT images showing an erosive lesion of the right petrous bone, centered at the right vestibular aqueduct opening (endolymphatic sac). The lesion is eroding the posterolateral wall of the jugular fossa. There is also erosion of the posterior wall of the right IAC, however the right IAC itself is still intact. There are scattered bony spicules seen within the lesion.
Axial T1 and axial T2 precontrast images, respectively, at the level of Cerebellopontine angle. There is a hyperintense multilobulated lesion occupying the right endolymphatic sac space. There is also a central area of low signal intensity which enhances post-gadolinium.T1-weighted post-gadolinium axial and coronal images, respectively. There is a central area of enhancement indicating hypervascularity. Low-signal intensities within the lesion represent intratumoral bony spicules.
Magnetic Resonance Imaging Of Inner Ear
MR IMAGING IN INNER EAR PATHOLOGY Moderator- PROF & HOD . DR R.K. GOGOI Presented by :: Sarbesh Tiwari
Introductio nThe ear functions both as an organ of hearing and as an organ of equilibrium 2
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 3
External EarPINNA (auricle) : # sixth week of embryonic life, # six tubercles appear around 1st branchial cleft. # They progressively coalesce to form the auricleExternal 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 4
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 5
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 6
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). 7
• 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 8
• 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. 9
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 Inner membranous1. bony cochlea labyrinth2. vestibule 1. Cochlear duct3. three bony semicircular 2. Utricle canals 3. Saccule4. Vestibular and cochlear 4. Three membranous aqueduct semicircular canals 5. Endolymphatic system 10
Bony labyrinth1. 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. 11
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 12
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. 13
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 basilarmembrane, which supports theorgan of corti,(b) the Reissners membranewhich separates it from thescala vestibuli,(c) the stria vascularis, whichcontains vascular epitheliumand is concerned withsecretion of endolymph. 14
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 footplateEndolymphatic 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 15
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) intoA. Smaller superior part• Superior vestibular N.• Facial NerveB. Larger Inferior part• Inferior vestibular N.• Cochlear nerve. 16
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 Inferior petrosal sinus vein of vestibular aqueduct Transverse sinus. 17
Cross sectional anatomy of inner ear Fig.1.-----Axial HRCT of Inner EarWhite arrowhead : Modiolus with cochlea Black arrowhead : VestibuleWhite arrow : I A C Black arrow : Posterior semicircular canal 18
Cross sectional anatomy of inner ear Fig. 2– Axial heavily T2 WI Fig. 3– Axial heavily T2 WIAxial images shows basal turn of cochlea Middle and apical turns with the modiolusand osseous spiral lamina (arrowhead) and the spiral lamina (curved arrow) dividing the cochlea into scala vestibuli and scala tympani . The nerves are seen in CP angle. 19
Cross sectional anatomy of inner ear Fig. 3– Sagittal T2 MR ImagesShowing the four nerves within IAC : The facial nerve (arrow head), cochlear nerve(curved arrow) and superior and inferior vestibular nerves (arrowhead) 20
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 21
IMAGING PROTOCOL -- MRI Inner ear Imaging Tumors and infection• 1.5 or 3 Tesla MRI is preferred• Sedation used in most children • Precontrast brain with thin section• 3D volumetric CISS in axial plane through the CPA- IAC region with coronal and sagittal reformation and MIP • MRA/ MRV as required reconstruction• Slice thickness of 0.4 – 0.7 mm • Post contrast fat sat.• 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. 22
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. 23
The 3 D reconstruction of inner ear done with post-processing by maximumintensity projection(MIP) and multi-planar reconstruction(MPR) by using 3D-CISS sequence 24
Congenital malformation of inner earCochlear abnormalities are numerous and Jackler et al classified them on the basisof arrested development during organogenesis 26
TIMELINE OF CONGENITAL MALFORMATION OF INNER EAR 27
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 cavityMRI : 8th cranial nerve not visualized on MR images Associated with skull base, CVJ and vascular anomalies 28
Axial CT : Flat middle ear cavity and Coronal CT : Atretic internal auditoryhypoplastic petrous bone canal Sagittal MRI : single nerve within the 29 IAC, suggesting absent 8th nerve
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 poordifferentiation of membranouslabyrinth as well resulting insevere to profound hearing loss 30
Confluence of cochlea and vestibule in a Common cavitycystic cavity with no internal architecture Absence of cochlear nerve 31
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 semicircularcanal 4. dense otic bone is presentwhere cochlea would be 32
Axial CT images shows dilated globose Coronal CT images shows malformedvestibule (arrow head) , dense sclerotic bone dilated lateral semicircular canal (straightwhere cochlea should be (curved arrow) arrow) with stunted superior semicircular, and a stunted dilated posterior semicircular canal (curved arrow)canal (straight arrow). 33
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 34
Axial CT & MRI :- Small cochlear bud and abnormally small and deformed vestibule 35 Stenotic IAC
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 36
Axial CT shows absence of Slightly lower level shows normalthe modiolus with a cystic basal turncochlear apex (straightarrow) , dilatation ofvestibular aqueduct(arrowhead) and vestibule(curved arrow) 37 Coronal CT images shows the cystic cochlear apex
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 canal- vestibule 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. 38
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. 39
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. 41
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 43
CT: 1. Posterior carotid plate is absent 2. Horizontal part of carotid canalappears to merge with lateralcochlear promontoryMRI : 1. Routine MR sequence are nothelpful. 2. MRA shows unusualposterolateral course of ICA 44
• 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. 45
Venous variants1. High riding Jugular bulb : Large jugular bulb reaching above the internal auditory canal with intact sigmoid plate2. 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 47
LABYRINTHITISInflammation of membranouslabyrinth.Viruses are the most commonetiologic agents, but can bebacterial or autoimmune .Types:1. Tympanic labyrinthitis : Infection spreads from middle ear via oval or round window or labyrinthine fistula2. Meningogenic : Infection spreads along CSF spaces via IAC or cochlear aqueduct. Usually bilateral.3. Hematogenic labyrinthitis : spread of infection by blood- stream. Virus e.g, measles and mumps, syphilis etc4. Post traumatic labyrinthitis. 50
Imaging features:CT : # Usually normal in acute stage # Ossification of membranous labyrinth in late chronic phaseMRI : 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. 51
Axial MRI in patient with suppurativelabyrinthitis. Enhancement of internalauditory canal, cochlea, andvestibule. 52
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 labyrinthMR Imaging :- Loss of the normal high signal on T2- weighted images from displacement of the endolymphatic fluid is suggestive of this diagnosis. 53
CHOLESTEATOMA WITH COMPLICATIONMRI 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. 55
CHOLESTEATOMA WITH COMPLICATIONA . 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. 56
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, recurrentbacterial meningitis, and intracranial abscess are rare complications, which, nevertheless, require an urgent CT/MR imaging examination 58
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 59
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 Meckels cave. 61
CT scan :1. Erosive lysis with ill-defined irregular edges of petrous apex2. Peripheral enhancement of petrous apex with dural enhancement and thickeningMRI:1. Fluid signal intensity in petrous apex often with peripheral enhancement2. More sensitive in detecting dural thickening and enhancement as well as leptomeningitis, cerebritis and 62 cerebral abscess
BELL’S PALSY• Bells 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. 67
•On MRI imaging enhancement of the facial nerve within thetympanic portion of the facial nerve canal supports thediagnosis.•Reported enhancement rates vary from 57% to 100%.•Typically long segments of the facial nerve enhance in auniformly linear fashion 68
Facial SchwannomasFacial nerve Schwannoma are uncommon tumors arising from the Schwann cell sheathSite : Geniculate ganglion, followed by labyrinthine and tympanic segment.Pathology : Originate from surface of the nerve, and splay the nerve fibres over their eccentric growthC/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 featuresHRCT : Enhancing soft tissue density lesion along facial nerve Intracanalicular or CP angle tumor can cause bony erosion of anterosuperior portion of IACMRI: 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 70
CT SCAN : focal enlargement of thelabyrinthine segment of the facial nerveMRI: homogeneously enhancing massfilling the internal auditory canal withextension into the CP angle andlabyrinthine segmentDiagnosis : Facial Nerve Schwannoma 71
The axial T1-weighted post-contrast MR image (left) shows homogeneousenhancement of the mass (between arrows).The bone algorithm CT (right)at the same level shows focal enlargementof the descending segment with extension toward the external auditorycanal.Diagnosis : Schwannoma of the mastoid segment of facial nerve. 72
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 LesionsAge : 3rd to 6th decade without sex predilectionSite : Geniculate fossa followed by IACC/F: Facial nerve paralysis progressing over weeks. Sensorineural hearing loss and pulsatile tinnitus may occur if there is erosion of otic capsule. 73
IMAGING FINDINGSMRI : # 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 lesionCT Scan : Enables exquisite visualization of associated bone changes Tumor causes erosion which are irregular with indistinct margins giving a “Honeycomb” pattern of eroded bone. 74
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 glial- schwann cell interface• Morphology : # Entirely intracanalicular # Intracanalicular with cisternal component ‘ Ice- cream cone appearance’. # Rarely purely intracisternal. 80
• 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. 81
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. 82
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 84
Imaging featuresNECT : # Frequently hyperdense with focal areas of calcification # Bony hyperostosis of petrous boneCECT : 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) 85
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. 87
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 boneUnique names associated with location: - Jugular bulb – Glomus jugulare Middle ear -- Glomus tympanicum Carotid body – Carotid body tumor Vagus nerve ganglion-- Glomus vagale 88
• Clinical feature: Pulsating tinnitus with conductive hearing loss Invasion into cochlea leads to sensorineural hearing loss Otoscopy : Tympanic membrane appears blue : Isolated to middle earcavity Soft tissue density protruding fromcochlear promontory . Homogenous enhancement on postcontrast scan.Confined to jugular fossa and large atpresentationInvades the hypo-tympanum andinfralabryrinth compartmentTumor can follow the Jugular venous systemupto lower cervical jugular vein. 89
MRI features :T1WI – Low signal intensityT2WI – High signal IntensityT1C+ -- Marked intense enhancementSalt – pepper appearance (T1 + T2) : Salt represents areas of hemorrhages and pepper represents areas of flow void. 90
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. 91
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 94
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. 95
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. 96
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 +VertigoImaging : CECT a. Heterogeneous lesion with “moth- eaten” retrolabyrinth petrous bone b. Intratumoral spiculated bone seen c. Intense enhancement in seen 97
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 98
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. 99
ConclusionMR provides accurate anatomical delineation ofcomplex soft tissue of inner ear3D reconstruction improves preimplantevaluationDetailed delineation of 7th & 8th nerve complex intemporal bone as well as membranous labyrinthDepiction of tumor size and extension into CPangle determines the approach to surgicalremoval. 100
References1. Diagnostic Radiology- Neuroradiology – AIIMS – MAMC- PGI Course series . 3rd edition.2. CT and MRI of whole body – John R Haaga 5th edition3. 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):683-984. 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 13215. 101