Imaging plays an important part in the work-up of cochlear implant candidates, and an understanding of imaging evaluation procedures is essential. The CI Surgeon must be familiar with imaging findings that contraindicate implantation (absence of the cochlea or cochlear nerve) and with those that could significantly alter surgery (facial nerve dehiscence, cochlear ossification). It is also imperative to be familiar with the growing number of imaging options (particularly magnetic resonance [MR] imaging pulse sequences) to optimize evaluation of cochlear implant candidates. CI Surgeon will assume an expanding role in evaluating affected patients as the frequency of cochlear implantation continues to increase.
Imaging requirements for cochlear implantation prepared by Dr. Prahlada N.B, Karnataka ENT Hospital & Research Center, Chitradurga.
Imaging Requirements for Cochlear Implantation. Dr. Prahlada N.BMBBS, MS, MBA, MHAENT, HEAD - NECK SURGERY & SKULL BASE SURGERYBasaveshwara Medical College & Hospital Chitradurga
Congenital absence of the cochlear nerve with an isolated cochlea. Axial and oblique sagittal T2-weighted fast spin-echo MR images of a 5-year-old girl with profound unilateral hearing loss (patient C8).A, Image of the normal left side shows the normal contours of the cochlea and other labyrinthine structures.B, IAC is of normal size and contains four nerves of comparative size. Cochlear nerve lies anteroinferiorly (arrow).C, Right side shows a deformed contour of the IAC (black arrow). Low-signal-intensity bar separates the fundus of the IAC from the modiolus (white arrow), which was confirmed to be bony at CT. We describe this as an isolated cochlea. The arrowhead indicates a singular canal containing the nerve of the posterior semicircular canal.D, Oblique sagittal image of the distal IAC shows a solitary nerve within the superior aspect of the small, deformed canal (arrow). The cochlear nerve is absent in this patient with normal facial nerve function.
Imaging requirements for cochlear implantation
BMCH, ChitradurgaImaging Requirements forCochlear ImplantationDr. Prahlada N.BMBBS, MS, MBA, MHAENT, HEAD – NECK & SKULL BASE SURGERYBasaveshwara Medical College & HospitalChitradurga
4/16/2013 24/16/2013 2BMCH, Chitradurga• Determine patients withContraindications for CI• Determine the approach• As a guide during surgeryWhy Imaging?Objectives
4/16/2013 34/16/2013 3BMCH, Chitradurga• HRCT temporal bone.• MRIWhat type of ImagingProtocol
4/16/2013 44/16/2013 4BMCH, Chitradurga• Evaluates the status of– Mastoid pneumatisation– Thickness of the cortical bone– Middle ear aeration– The round window nicheRole of HRCTProtocol
4/16/2013 54/16/2013 5BMCH, Chitradurga• It may display anatomic middle earvariations of surgical importance suchas:– Dehiscent facial nerve– Low lying dura– High jugular bulb and– Aberrant carotid arteryRole of HRCTProtocol
4/16/2013 64/16/2013 6BMCH, Chitradurga• CT demonstrates anomalies of the bonylabyrinth such as– Paget’s disease– Otosclerosis– Postmeningitis stenosis of the roundwindow niche.Role of HRCTProtocol
4/16/2013 74/16/2013 7BMCH, Chitradurga• HRCT scans are performed on a 64-slice volume scanner in a straight axialplane: kV: 140, mA: 350, matrix: 512 ×512• Slice thickness: 0.625 mm/10.63,0.531:1• Scan field of view (FOV): 32 cm, displayFOV: 9.6 cmHRCTProtocol
4/16/2013 84/16/2013 8BMCH, Chitradurga• The original isometric volume data isused to obtain Coronal reformattedimages.• The images are reviewed with a high-resolution bone algorithm, using a smallFOV for separate right and left eardocumentation.HRCTProtocol
4/16/2013 94/16/2013 9BMCH, Chitradurga• Coronal reformations along with 3Dmaximum intensity projection (MIP)reconstructions.HRCTProtocol
4/16/2013 104/16/2013 10BMCH, Chitradurga• To identify active fibrosis• Identify cochlear fluid fibrosis• To depict cochlear nerve agenesis andcochlear anomalies• To detect an occult acoustic nervetumour• To detect brainstem anomalies– Trauma, Congenital.Role of preoperative MRIProtocol
4/16/2013 114/16/2013 11BMCH, Chitradurga• MRI scans are performed on 1.5-T MRwith an 8-channel head coil.• Sedation is used in most patients.• A 3D-FIESTA (fast imaging enablingsteady-state acquisition) axial sequence(TR: 5.5, TE: 1.7/Fr, FOV: 16 × 16, slicethickness: 1.0/−0.5, matrix: 320 × 320,NEX: 6.0) is performedMRIProtocol
4/16/2013 124/16/2013 12BMCH, Chitradurga• A 3D-FIESTA sequence is also acquiredin a DIRECT OBLIQUE SAGGITTALPLANE (TR: 6.7, TE: 2.1/Fr, FOV: 12 ×12, slice thickness: 1.0/−0.5, matrix: 384× 320, NEX: 6.0) perpendicular to theVII–VIII nerve complexes.MRIProtocol
BMCH, ChitradurgaMRI Direct Oblique Saggittal ViewCadaver Dissection showing Direct Oblique Sagittal View.
BMCH, ChitradurgaMRI Direct Oblique Saggittal View
BMCH, ChitradurgaMRI - Constructive InterferenceSteady State (CISS)Science Photo libraryAdvantage : Combination of high signal levels andextremely high spatial resolution.
4/16/2013 164/16/2013 16BMCH, Chitradurga• Provides better resolution than withreformations from an axial sequence;Provides better delineation of the nerves.• A routine T2W axial sequence throughthe brain is obtained in all patients.MRIProtocol
4/16/2013 174/16/2013 17BMCH, Chitradurga• Advantages of MRI over CT:– Distinguish between cochlear fibrosis andossification– Diagnose cochlear nerve agenesis.– MRI may depict unsuspected acousticnerve or central acoustic pathwayanomalies including acoustic nervetumours.HRCT Vs MRIProtocol
4/16/2013 184/16/2013 18BMCH, Chitradurga• Disadvantages of MRI– Additive cost as MRI does not replace CT.– Good quality MR images in deaf patientsare more difficult to obtain, as difficulties ofcommunication may lead to movementartefacts.– Sedation is needed in children.HRCT Vs MRIProtocol
BMCH, ChitradurgaNORMAL ANATOMY - HRCTImaging requirements for Cochlear Implantation
BMCH, ChitradurgaInferior view of 3D maximum intensityprojection (MIP) reconstructed from 3T MR.Note the cochlear nerve anteriorly and both saccular and posteriorbranches of the inferior vestibular nerves posteriorly.John I. Lane Robert J. Witte: The Temporal Bone, An Imaging Atlas
BMCH, ChitradurgaSuperior view of 3D MIP reconstructed from 3TMR.Note the facial nerve anteriorly and the superior vestibular nerveposteriorlyJohn I. Lane Robert J. Witte: The Temporal Bone, An Imaging Atlas
BMCH, ChitradurgaPRE-SURGICAL EVALUATIONImaging requirements for Cochlear Implantation
4/16/2013 374/16/2013 37BMCH, Chitradurga• An IAM less than 2 mm in diameter increasesthe risk of a congenital absence or of severehypoplasia of the acoustic nerve.• An absent or narrow modiolus (diameter lessthan 3 mm in CT, or a modiolar surface lessthan 4 mm2 in MR) are at risk of absence ofcochlear nerve.• The modiolus is a bone area of low signalintensity in T2WI, located at the base of thecochlea. It represents the exit of the cochlearnerve.1. Size of the IAMKeyPoints
4/16/2013 384/16/2013 38BMCH, Chitradurga• Exploration of the IAM by MR with CISSsequence and sagittal reconstructions allowsthe measurement of the diameter of thecochlear nerve.• Cochlear nerve diameter is measured in relationto the facial nerve taken as reference.• Normally, the cochlear nerve lays on the inferiorpart of the IAM and• Cochlear nerve is larger than the facial nerve.• Its diameter is approximately of 0.4 mm.3. Cochlear nerve statusKeyPoints
BMCH, ChitradurgaModiolusThe modiolus is a conical shaped central axis in the cochlea. Itconsists of spongy bone and the cochlea turns approximately 2.5times around it. The spiral ganglion is situated inside it.Basic human anatomy - Orahilly, Müller, Carpenter & Swenson
BMCH, ChitradurgaCochlear nerve deficiencyC. Isolated Cochlea. D. Absent Cochlear Nerve.Christine M. Imaging Findings of Cochlear Nerve Deficiency. AJNR 2002 23: 635-643
BMCH, ChitradurgaAbsent ModiolusAxial section of the cochlea of a 4-year-old boy with Cornelia deLange syndrome. Note the diminished width and height of cochlearupper turns with an absent modiolus in the section from the patientwith Cornelia de Lange syndrome (A) as compared with a 2-year-old control with normal hearing (B).J. Kima: Temporal Bone CT Findings in Cornelia de Lange Syndrome. AJNR March 2008 29: 569-573
4/16/2013 424/16/2013 42BMCH, Chitradurga• Anomaly of the course of the:• Facial nerve• The carotid artery• The sigmoid sinus• Venous variants such mastoid emissaryveins2. Neurovascular AnomalyKeyPoints
4/16/2013 434/16/2013 43BMCH, Chitradurga• Facial nerve with an abnormal coursethrough the mastoid cells is at significantrisk during implantation.• Facial nerve injury can occur during– Facial recess approach.– Insertion of electrodes.• Facial nerve monitoring is an option.2. Neurovascular AnomalyKeyPoints
4/16/2013 444/16/2013 44BMCH, Chitradurga• Study:– The number of cochlear turns– Symmetry of scala chambers– Status of the modiolus– Status of the posterior membranouslabyrinth.mbranous labyrinth anomalyKeyPoints
4/16/2013 454/16/2013 45BMCH, Chitradurga• Congenital anomalies discovered duringpreoperative imaging studies can be thecause of the sensorineural hearing loss.• Can increase the surgical risk to have a`Gusher-ear during the electrodeinsertion within the round window4. Membranous labyrinthanomalyKeyPoints
4/16/2013 464/16/2013 46BMCH, Chitradurga• Cochlear ossification or fibrosis may:– Limit the full insertion of the electrode arrayor– Modify the choice of the cochlear implant– Modify the way of Electrode insertion.ndo- and perilymphatic fluidStatusKeyPoints
4/16/2013 474/16/2013 47BMCH, Chitradurga• Stenosis of the round window niche mayoccur in bone remodelling lesions suchas:– Paget’s disease– Otosclerosis– Lobstein disease– Post-meningitis labyrinthitis.Status of Bony Labyrinth &Round Window NicheKeyPoints
BMCH, ChitradurgaPaget’s DiseaseAxial CT scan demonstrates diffuse expansion and sclerosis of thebones of the skull base, characteristic of Paget disease.S. Vattotha, et al. A Compartment-Based Approach for the Imaging Evaluation of Tinnitus.AJNR 2010 31: 211-218
BMCH, ChitradurgaOtosclerosisFenestral otosclerosis showing a fissula ad fenestram.Medical Observer. Australia
BMCH, ChitradurgaOsteogenesis ImperfectaThe labyrinthine segment, the geniculate ganglion (arrowheads), and the proximaltympanic segment of the facial nerve canal are severely involved and haveindistinct, irregular margins. Progression of demineralization is also demonstrated inpericochlear areasOsteogenesis Imperfecta of the Temporal Bone: CT and MR Imaging in Van der Hoeve-de Kleyn SyndromeHatem Alkadhi . AJNR 2004 25: 1106-1109
BMCH, ChitradurgaPost-meningitis labyrinthitis.Axial CT scan showing advanced labyrinthitis ossificans in both ears.Vanessa Y.J. Tan et al: Acoustic brainstem implant in a post-meningitis deafened child—Lessons learned.International Journal of Pediatric Otorhinolaryngology Volume 76, Issue 2, February 2012, Pages 300–302
BMCH, ChitradurgaCONGENITAL ANOMALIESImaging requirements for Cochlear Implantation
4/16/2013 544/16/2013 54BMCH, Chitradurga• Michel deformity• Common cavity deformity• Cochlear aplasia• Hypoplastic cochlea• Incomplete partition types– I (IP-I) and– II (IP-II) (Mondini deformity).Cochlear anomaliesClassificationSennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
4/16/2013 554/16/2013 55BMCH, Chitradurga• Incomplete partition type I or Cysticcochleovestibular malformation:– Cochlea lacks the entire modiolus andcribriform area, resulting in a cysticappearance, and there is an accompanyinglarge cystic vestibule.mplete partition of CochleaClassificationSennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
BMCH, ChitradurgaIncomplete partition type I or Cysticcochleovestibular malformationAxial Section showing Cystic appearing Cochlear and Large cysticVestibule.University of Washington Department of Radiology.
BMCH, ChitradurgaCommon cystic cavityUniversity of Washington Department of Radiology.
BMCH, ChitradurgaIncomplete partition - IIClassic Mondini malformationUniversity of Washington Department of Radiology.
BMCH, ChitradurgaIncomplete partition - IIClassic Mondini malformationUniversity of Washington Department of Radiology.
BMCH, ChitradurgaIncomplete partition variantNormal basal turn of the Cochlear and Round WindowUniversity of Washington Department of Radiology.
BMCH, ChitradurgaIncomplete partition variant1.5 Turns of Cochlear with Confluence of the middle and apexresulting in Cystic apex. Enlarged vestibule with nomral Vestibularaqueduct are seen.University of Washington Department of Radiology.
4/16/2013 624/16/2013 62BMCH, Chitradurga• Incompelete Partition Type II or theMondini deformity:– A cochlea consisting of 1.5 turns (in whichthe middle and apical turns coalesce toform a cystic apex accompanied by adilated vestibule and enlarged vestibularaqueduct.mplete partition of CochleaClassification
4/16/2013 634/16/2013 63BMCH, Chitradurga• Michel deformity• Cochlear aplasia• Common cavity• Cochlear hypoplasia• IP-I (Cystic cochleovestibularmalformation),• IP-II (Mondini deformity)Clinical ClassificationClassificationSennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
4/16/2013 644/16/2013 64BMCH, Chitradurga• Absent Cochlear nerve– Diameter of IAM (mid-part) <3 mm• Absent Cochlear• Absent ModiulusContraindications for CINotoCI
4/16/2013 654/16/2013 65BMCH, Chitradurga• Cochlear ossification (partial or total;length in basal turn)• Hyperostosis of the round window niche• Persistent membranous labyrinthinflammation• Inner ear at risk of `Gusher:endolymphatic sac dilatation.Alternate SurgicalTechnique/Implant DeviceNotoCI
4/16/2013 664/16/2013 66BMCH, Chitradurga• Abnormal cochlear segmentation.• Deficient modiolus.• Semicircular canal or vestibulardilatation.• Stenosis of the basal turn.• Otosclerosis foci.• Paget’s disease.Alternate SurgicalTechnique/Implant DeviceNotoCI
BMCH, ChitradurgaDeficient ModiolusAxial T2-weighted FSE MR image of the right inner ear : The cochlearoutline is distorted, and the normal notch between the middle and apicalturns laterally (white arrow) is blunted. Note that the modiolus isdeficient (black arrow).H. Christian Davidson: MR Evaluation of Vestibulocochlear Anomalies Associated with LargeEndolymphatic Duct and Sac. AJNR 1999 20: 1435-1441,
BMCH, ChitradurgaDeficient ModiolusAxial T2-weighted FSE MR image in another patient shows severe dysplasia.The cochlea (C) appears as a common cavity, the internal architecture is lost,and the modiolus is absent. The vestibule also shows severe dysplasticchanges, including gross vestibular enlargement (V) and hypoplasia of thelateral semicircular canal (arrowhead). A portion of the enlarged endolymphaticduct is also apparent (asterisk).H. Christian Davidson: MR Evaluation of Vestibulocochlear Anomalies Associated with LargeEndolymphatic Duct and Sac. AJNR 1999 20: 1435-1441,
BMCH, ChitradurgaOtosclerosis of the CochleaDuring surgery it was noted that otosclerosis had filled the basalturn of the cochlea and obliterated the round window.Eric W. Sargent M.D., OTOSCLEROSIS: A Review for Audiologists
BMCH, ChitradurgaStenosis of the Basal Turn of the CochlearSmall calcification in basal turn of cochlea as a result of labyrinthitisossificans.Eric Beek and Frank Pameijer: Temporal Bone Pathology.
BMCH, ChitradurgaSemicircular Canal dilatationThere is a widening and shortening of the lateral semicircularcanal.Eric Beek and Frank Pameijer: Temporal Bone Pathology.
BMCH, ChitradurgaVestibular dilatationThe vestibule is relatively large (arrow).Eric Beek and Frank Pameijer: Temporal Bone Pathology.
BMCH, ChitradurgaHypoplastic Mastoid ProcessRight side, the mastoid air cells are under pneumatized. There isno identifiable external auditory canal.American College of Radiology
BMCH, ChitradurgaNormal Vs Sclerosed MastoidFirst: Normal pneumatized mastoid with aerated cells. The mastoidis completely sclerotic - no air cells are present.
BMCH, ChitradurgaChronic Otitis MediaThe eardrum is thickened. A small amount of soft tissue (arrow) isvisible between the scutum and the ossicular chain but no erosion ispresent. This favors the diagnosis of chronic otitis media.
BMCH, ChitradurgaDehiscent Facial NerveRobert J. Witte, MD: Pediatric and Adult Cochlear Implantation: RadioGraphics 2003; 23:1185–1200
BMCH, ChitradurgaDehiscent Facial NervePatient also has signs of Chronic Otitis MediaNIRA A. GOLDSTEIN, MD et al., Intratemporal complications of acute otitis media in infants and children. Otolaryngology -Head and Neck Surgery Volume 119, Issue 5, November 1998, Pages 444–454.
BMCH, ChitradurgaMastoid Emissary VeinH Alsherhri1, B Alqahtani2, M Alqahtani3: Year : 2011 | Volume : 17 | Issue : 3 | Page : 123-126
BMCH, ChitradurgaAnterior Bulging Sigmoid SinusThe sigmoid sinus can protrude into the posterior mastoid.It can be accidentally lacerated during a mastoidectomy .Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, ChitradurgaHigh Jugular BulbThe jugular bulb is often asymmetric, with the right jugular bulbusually being larger than the left. If it reaches above the posteriorsemicircular canal it is called a high jugular bulb.Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, ChitradurgaJugular Bulb DiverticulumRarely an out-pouching is seen – this is known as a jugularbulb diverticulum.Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, ChitradurgaDehiscent jugular bulbOn the left a dehiscent jugular bulb (blue arrow).This can be dangerous during myringotomy.Note also the bulging sigmoid sinus (yellow arrow).Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, ChitradurgaAberrant internal carotid arteryIn patients with an aberrant internal carotid artery the cervical partof the internal carotid artery is absent. It is replaced by theascending pharyngeal artery which connects with the horizontalpart of the internal carotid artery.It courses through the middle ear.Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, ChitradurgaAberrant internal carotid arteryOn the left coronal images of the same patient. On the right sidethe internal carotid artery is separated from the middle ear (bluearrow). On the left side the internal carotid artery courses throughthe middle ear (red arrow)Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands