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BMCH, Chitradurga
Imaging Requirements for Cochlear Implantation
Dr. Prahlada N.BMBBS, MS, MBA, MHA
ENT, HEAD – NECK & SKULL BASE SURGERYBasaveshwara Medical College & Hospital
Chitradurga
4/16/2013 24/16/2013 2 BMCH, Chitradurga
• Determine patients with Contraindications for CI
• Determine the approach• As a guide during surgery
Why Imaging?Ob
ject
ives
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• HRCT temporal bone.• MRI
What type of ImagingPr
otoc
ol
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• Evaluates the status of –Mastoid pneumatisation – Thickness of the cortical bone–Middle ear aeration– The round window niche
Role of HRCTPr
otoc
ol
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• It may display anatomic middle ear variations of surgical importance such as: – Dehiscent facial nerve – Low lying dura – High jugular bulb and – Aberrant carotid artery
Role of HRCTPr
otoc
ol
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• CT demonstrates anomalies of the bony labyrinth such as – Paget’s disease – Otosclerosis – Postmeningitis stenosis of the round
window niche.
Role of HRCTPr
otoc
ol
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• HRCT scans are performed on a 64-slice volume scanner in a straight axial plane: kV: 140, mA: 350, matrix: 512 × 512
• Slice thickness: 0.625 mm/10.63, 0.531:1
• Scan field of view (FOV): 32 cm, display FOV: 9.6 cm
HRCTPr
otoc
ol
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• The original isometric volume data is used to obtain Coronal reformatted images.
• The images are reviewed with a high-resolution bone algorithm, using a small FOV for separate right and left ear documentation.
HRCTPr
otoc
ol
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• Coronal reformations along with 3D maximum intensity projection (MIP) reconstructions.
HRCTPr
otoc
ol
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• To identify active fibrosis• Identify cochlear fluid fibrosis• To depict cochlear nerve agenesis
and cochlear anomalies• To detect an occult acoustic nerve
tumour• To detect brainstem anomalies– Trauma, Congenital.
Role of preoperative MRIPr
otoc
ol
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• MRI scans are performed on 1.5-T MR with an 8-channel head coil.
• Sedation is used in most patients. • A 3D-FIESTA (fast imaging enabling
steady-state acquisition) axial sequence (TR: 5.5, TE: 1.7/Fr, FOV: 16 × 16, slice thickness: 1.0/−0.5, matrix: 320 × 320, NEX: 6.0) is performed
MRIPr
otoc
ol
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• A 3D-FIESTA sequence is also acquired in a DIRECT OBLIQUE SAGGITTAL PLANE (TR: 6.7, TE: 2.1/Fr, FOV: 12 × 12, slice thickness: 1.0/−0.5, matrix: 384 × 320, NEX: 6.0) perpendicular to the VII–VIII nerve complexes.
MRIPr
otoc
ol
BMCH, Chitradurga
MRI Direct Oblique Saggittal ViewCadaver Dissection showing Direct Oblique Sagittal View.
BMCH, Chitradurga
MRI Direct Oblique Saggittal View
BMCH, Chitradurga
MRI - Constructive Interference Steady State (CISS)
Science Photo library
Advantage : Combination of high signal levels andextremely high spatial resolution.
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• Provides better resolution than with reformations from an axial sequence; Provides better delineation of the nerves .
• A routine T2W axial sequence through the brain is obtained in all patients.
MRIPr
otoc
ol
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• Advantages of MRI over CT:– Distinguish between cochlear fibrosis
and ossification– Diagnose cochlear nerve agenesis. –MRI may depict unsuspected acoustic
nerve or central acoustic pathway anomalies including acoustic nerve tumours.
HRCT Vs MRIPr
otoc
ol
4/16/2013 184/16/2013 18 BMCH, Chitradurga
• Disadvantages of MRI– Additive cost as MRI does not replace
CT. – Good quality MR images in deaf
patients are more difficult to obtain, as difficulties of communication may lead to movement artefacts.
– Sedation is needed in children.
HRCT Vs MRIPr
otoc
ol
BMCH, Chitradurga
NORMAL ANATOMY - HRCTImaging requirements for Cochlear Implantation
BMCH, Chitradurga
Frontal
Medial
Occipital
Lateral
1. Temporomandibular joint (glenoid roof and articular disc) 2. Pharyngotympanic tube (auditory tube) 3. Internal carotid artery 4. External acoustic meatus 5. Facial canal 6. Internal jugular vein 7. Mastoid process 8. Sigmoid sinus 9 Carotid canal 10. Malleus (handle) 11. Tensor tympani muscle (canal) 12. Middle ear 13. Incus (long limb) 14. Cochlea (basal turn) 15 Sinus tympani 16 Vestibular aqueduct 17 Round window
BMCH, Chitradurga
Frontal
Medial
Occipital
Lateral
1. Temporomandibular joint (glenoid roof and articular disc) 2. Pharyngotympanic tube (auditory tube) 3. Internal carotid artery 4. External acoustic meatus 5. Facial canal 6. Internal jugular vein 7. Mastoid process 8. Sigmoid sinus 9 Carotid canal 10. Malleus (handle) 11. Tensor tympani muscle (canal) 12. Middle ear 13. Incus (long limb) 14. Cochlea (basal turn) 15 Sinus tympani 16 Vestibular aqueduct 17 Round window
BMCH, Chitradurga
2 Malleus (handle) 3 Incus (long limb) 4 Cochlea 5 Stapes 6 Oval window 7 Sinus tympani 8 Facial canal 9 Internal jugular vein (bulb) 10 Mastoid 11 Epitympanic recess 12 Malleus (head) 13 Incus (short limb) 14 Internal acoustic meatus15 Aditus to mastoid antrum 16 Vestibule 17 Posterior semicircular canal 18 Mastoid antrum 19 Lateral semicircular canal
Frontal
Medial
Occipital
Lateral
BMCH, Chitradurga
2 Malleus (handle) 3 Incus (long limb) 4 Cochlea 5 Stapes 6 Oval window 7 Sinus tympani 8 Facial canal 9 Internal jugular vein (bulb) 10 Mastoid 11 Epitympanic recess 12 Malleus (head) 13 Incus (short limb) 14 Internal acoustic meatus15 Aditus to mastoid antrum 16 Vestibule 17 Posterior semicircular canal 18 Mastoid antrum 19 Lateral semicircular canal
Frontal
Medial
Occipital
Lateral
BMCH, Chitradurga
1 Geniculate ganglion 2 Facial nerve (first part) 3 Facial nerve (second part) 4 Internal acoustic meatus 5 Tympanic cavity6 Vestibule 7 Posterior semicircular canal 8 Mastoid antrum 9 Lateral semicircular canal 10Sigmoid sinus 11 Anterior (superior) semicircular canal 12 Mastoid cells
Frontal
Medial
Occipital
Lateral
BMCH, Chitradurga
Frontal
Medial
Occipital
Lateral
1 Geniculate ganglion 2 Facial nerve (first part) 3 Facial nerve (second part) 4 Internal acoustic meatus 5 Tympanic cavity6 Vestibule 7 Posterior semicircular canal 8 Mastoid antrum 9 Lateral semicircular canal 10 Sigmoid sinus 11 Anterior (superior) semicircular canal 12 Mastoid cells
BMCH, Chitradurga
NORMAL ANATOMY - MRIImaging requirements for Cochlear Implantation.
BMCH, Chitradurga
BMCH, Chitradurga
BMCH, Chitradurga
BMCH, Chitradurga
BMCH, Chitradurga
BMCH, Chitradurga
BMCH, Chitradurga
BMCH, Chitradurga
Inferior view of 3D maximum intensityprojection (MIP) reconstructed from 3T MR.
Note the cochlear nerve anteriorly and both saccular and posterior branches of the inferior vestibular nerves posteriorly.
John I. Lane Robert J. Witte: The Temporal Bone, An Imaging Atlas
BMCH, Chitradurga
Superior view of 3D MIP reconstructed from 3T MR.
Note the facial nerve anteriorly and the superior vestibular nerve posteriorly
John I. Lane Robert J. Witte: The Temporal Bone, An Imaging Atlas
BMCH, Chitradurga
PRE-SURGICAL EVALUATIONImaging requirements for Cochlear Implantation
4/16/2013 374/16/2013 37 BMCH, Chitradurga
• An IAM less than 2 mm in diameter increases the risk of a congenital absence or of severe hypoplasia of the acoustic nerve.
• An absent or narrow modiolus (diameter less than 3 mm in CT, or a modiolar surface less than 4 mm2 in MR) are at risk of absence of cochlear nerve.
• The modiolus is a bone area of low signal intensity in T2WI, located at the base of the cochlea. It represents the exit of the cochlear nerve.
1. Size of the IAMKe
y Po
ints
4/16/2013 384/16/2013 38 BMCH, Chitradurga
• Exploration of the IAM by MR with CISS sequence and sagittal reconstructions allows the measurement of the diameter of the cochlear nerve.
• Cochlear nerve diameter is measured in relation to the facial nerve taken as reference.
• Normally, the cochlear nerve lays on the inferior part of the IAM and
• Cochlear nerve is larger than the facial nerve.• Its diameter is approximately of 0.4 mm.
3. Cochlear nerve statusKe
y Po
ints
BMCH, Chitradurga
ModiolusThe modiolus is a conical shaped central axis in the cochlea. It consists of spongy bone and the cochlea turns approximately 2.5 times around it. The spiral ganglion is situated inside it.
Basic human anatomy - O'rahilly, Müller, Carpenter & Swenson
BMCH, Chitradurga
Cochlear nerve deficiencyC. Isolated Cochlea. D. Absent Cochlear Nerve.
Christine M. Imaging Findings of Cochlear Nerve Deficiency. AJNR 2002 23: 635-643
BMCH, Chitradurga
Absent ModiolusAxial section of the cochlea of a 4-year-old boy with Cornelia de Lange syndrome. Note the diminished width and height of cochlear upper turns with an absent modiolus in the section from the patient with 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 42 BMCH, Chitradurga
• Anomaly of the course of the:• Facial nerve • The carotid artery • The sigmoid sinus • Venous variants such mastoid
emissary veins
2. Neurovascular AnomalyKe
y Po
ints
4/16/2013 434/16/2013 43 BMCH, Chitradurga
• Facial nerve with an abnormal course through the mastoid cells is at significant risk during implantation.
• Facial nerve injury can occur during
– Facial recess approach. – Insertion of electrodes.
• Facial nerve monitoring is an option.
2. Neurovascular AnomalyKe
y Po
ints
4/16/2013 444/16/2013 44 BMCH, Chitradurga
• Study:– The number of cochlear turns – Symmetry of scala chambers– Status of the modiolus – Status of the posterior membranous
labyrinth.
4. Membranous labyrinth anomaly
Key
Poin
ts
4/16/2013 454/16/2013 45 BMCH, Chitradurga
• Congenital anomalies discovered during preoperative imaging studies can be the cause of the sensorineural hearing loss.
• Can increase the surgical risk to have a `Gusher-ear' during the electrode insertion within the round window
4. Membranous labyrinth anomaly
Key
Poin
ts
4/16/2013 464/16/2013 46 BMCH, Chitradurga
• Cochlear ossification or fibrosis may:– Limit the full insertion of the electrode
array or –Modify the choice of the cochlear
implant–Modify the way of Electrode insertion.
5. Endo- and perilymphatic fluid StatusKe
y Po
ints
4/16/2013 474/16/2013 47 BMCH, Chitradurga
• Stenosis of the round window niche may occur in bone remodelling lesions such as:– Paget’s disease– Otosclerosis– Lobstein disease – Post-meningitis labyrinthitis.
6. Status of Bony Labyrinth & Round Window Niche
Key
Poin
ts
BMCH, Chitradurga
Paget’s DiseaseAxial CT scan demonstrates diffuse expansion and sclerosis of the bones 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, Chitradurga
OtosclerosisFenestral otosclerosis showing a fissula ad fenestram.
Medical Observer. Australia
BMCH, Chitradurga
Osteogenesis ImperfectaThe labyrinthine segment, the geniculate ganglion (arrowheads), and the proximal tympanic segment of the facial nerve canal are severely involved and have indistinct, irregular margins. Progression of demineralization is also demonstrated in pericochlear areas
Osteogenesis Imperfecta of the Temporal Bone: CT and MR Imaging in Van der Hoeve-de Kleyn SyndromeHatem Alkadhi . AJNR 2004 25: 1106-1109
BMCH, Chitradurga
Post-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, Chitradurga
CONGENITAL ANOMALIESImaging requirements for Cochlear Implantation
4/16/2013 534/16/2013 53 BMCH, Chitradurga
• Cochlear• Vestibular• Semicircular canal, • Internal auditory canal (IAC)• Vestibular and • Cochlear aqueduct malformations.
Types of anomaliesCl
assifi
catio
n
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
4/16/2013 544/16/2013 54 BMCH, Chitradurga
• Michel deformity• Common cavity deformity• Cochlear aplasia• Hypoplastic cochlea• Incomplete partition types– I (IP-I) and – II (IP-II) (Mondini deformity).
Cochlear anomaliesCl
assifi
catio
n
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
4/16/2013 554/16/2013 55 BMCH, Chitradurga
• Incomplete partition type I or Cystic cochleovestibular malformation:– Cochlea lacks the entire modiolus and
cribriform area, resulting in a cystic appearance, and there is an accompanying large cystic vestibule.
Incomplete partition of Cochlea
Clas
sifica
tion
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
BMCH, Chitradurga
Incomplete partition type I or Cystic cochleovestibular malformation
Axial Section showing Cystic appearing Cochlear and Large cystic Vestibule.
University of Washington Department of Radiology.
BMCH, Chitradurga
Common cystic cavity
University of Washington Department of Radiology.
BMCH, Chitradurga
Incomplete partition - II Classic Mondini malformation
University of Washington Department of Radiology.
BMCH, Chitradurga
Incomplete partition - II Classic Mondini malformation
University of Washington Department of Radiology.
BMCH, Chitradurga
Incomplete partition variant Normal basal turn of the Cochlear and Round Window
University of Washington Department of Radiology.
BMCH, Chitradurga
Incomplete partition variant 1.5 Turns of Cochlear with Confluence of the middle and apex resulting in Cystic apex. Enlarged vestibule with nomral Vestibular aqueduct are seen.
University of Washington Department of Radiology.
4/16/2013 624/16/2013 62 BMCH, Chitradurga
• Incompelete Partition Type II or the Mondini deformity:– A cochlea consisting of 1.5 turns (in
which the middle and apical turns coalesce to form a cystic apex accompanied by a dilated vestibule and enlarged vestibular aqueduct.
Incomplete partition of Cochlea
Clas
sifica
tion
4/16/2013 634/16/2013 63 BMCH, Chitradurga
• Michel deformity• Cochlear aplasia• Common cavity • Cochlear hypoplasia• IP-I (Cystic cochleovestibular
malformation), • IP-II (Mondini deformity)
Clinical ClassificationCl
assifi
catio
n
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
4/16/2013 644/16/2013 64 BMCH, Chitradurga
• Absent Cochlear nerve– Diameter of IAM (mid-part) <3 mm
• Absent Cochlear• Absent Modiulus
Contraindications for CINo
to C
I
4/16/2013 654/16/2013 65 BMCH, Chitradurga
• Cochlear ossification (partial or total; length in basal turn)
• Hyperostosis of the round window niche
• Persistent membranous labyrinth inflammation
• Inner ear at risk of `Gusher': endolymphatic sac dilatation.
Alternate Surgical Technique/Implant Device
No to
CI
4/16/2013 664/16/2013 66 BMCH, Chitradurga
• Abnormal cochlear segmentation.• Deficient modiolus.• Semicircular canal or vestibular
dilatation.• Stenosis of the basal turn.• Otosclerosis foci.• Paget’s disease.
Alternate Surgical Technique/Implant Device
No to
CI
BMCH, Chitradurga
Deficient ModiolusAxial T2-weighted FSE MR image of the right inner ear : The cochlear outline is distorted, and the normal notch between the middle and apical turns laterally (white arrow) is blunted. Note that the modiolus is deficient (black arrow).
H. Christian Davidson: MR Evaluation of Vestibulocochlear Anomalies Associated with Large Endolymphatic Duct and Sac. AJNR 1999 20: 1435-1441
,
BMCH, Chitradurga
Deficient 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 dysplastic changes, including gross vestibular enlargement (V) and hypoplasia of the lateral semicircular canal (arrowhead). A portion of the enlarged endolymphatic duct is also apparent (asterisk).
H. Christian Davidson: MR Evaluation of Vestibulocochlear Anomalies Associated with Large Endolymphatic Duct and Sac. AJNR 1999 20: 1435-1441
,
BMCH, Chitradurga
Otosclerosis of the CochleaDuring surgery it was noted that otosclerosis had filled the basal turn of the cochlea and obliterated the round window.
Eric W. Sargent M.D., OTOSCLEROSIS: A Review for Audiologists
BMCH, Chitradurga
Stenosis of the Basal Turn of the Cochlear
Small calcification in basal turn of cochlea as a result of labyrinthitis ossificans.
Eric Beek and Frank Pameijer: Temporal Bone Pathology.
BMCH, Chitradurga
Semicircular Canal dilatationThere is a widening and shortening of the lateral semicircular canal.
Eric Beek and Frank Pameijer: Temporal Bone Pathology.
BMCH, Chitradurga
Vestibular dilatationThe vestibule is relatively large (arrow).
Eric Beek and Frank Pameijer: Temporal Bone Pathology.
4/16/2013 734/16/2013 73 BMCH, Chitradurga
• Hypoplastic mastoid process• Inflammed middle ear• Dehiscent or aberrant facial nerve• Mastoid emissary vein• Deep sigmoid sinus• Exposed jugular bulb• Aberrant carotid artery• Persistent stapedial artery
Increased Surgical Risk No
to C
I
BMCH, Chitradurga
Hypoplastic Mastoid ProcessRight side, the mastoid air cells are under pneumatized. There is no identifiable external auditory canal.
American College of Radiology
BMCH, Chitradurga
Normal Vs Sclerosed MastoidFirst: Normal pneumatized mastoid with aerated cells. The mastoid is completely sclerotic - no air cells are present.
BMCH, Chitradurga
Chronic Otitis MediaThe eardrum is thickened. A small amount of soft tissue (arrow) is visible between the scutum and the ossicular chain but no erosion is present. This favors the diagnosis of chronic otitis media.
BMCH, Chitradurga
Dehiscent Facial Nerve
Robert J. Witte, MD: Pediatric and Adult Cochlear Implantation: RadioGraphics 2003; 23:1185–1200
BMCH, Chitradurga
Dehiscent Facial NervePatient also has signs of Chronic Otitis Media
NIRA 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, Chitradurga
Mastoid Emissary Vein
H Alsherhri1, B Alqahtani2, M Alqahtani3: Year : 2011 | Volume : 17 | Issue : 3 | Page : 123-126
BMCH, Chitradurga
Anterior 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, Chitradurga
High Jugular BulbThe jugular bulb is often asymmetric, with the right jugular bulb usually being larger than the left. If it reaches above the posterior semicircular 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, Chitradurga
Jugular Bulb DiverticulumRarely an out-pouching is seen – this is known as a jugular bulb diverticulum.
Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, Chitradurga
Dehiscent 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, Chitradurga
Persistent Stapedial Artery
www.neuroangio.org
BMCH, Chitradurga
Aberrant internal carotid arteryIn patients with an aberrant internal carotid artery the cervical part of the internal carotid artery is absent. It is replaced by the ascending pharyngeal artery which connects with the horizontal part 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, Chitradurga
Aberrant internal carotid arteryOn the left coronal images of the same patient. On the right side the internal carotid artery is separated from the middle ear (blue arrow). On the left side the internal carotid artery courses through the middle ear (red arrow)
Temporal bone – Pathology: Eric Beek and Frank PameijerRadiology department of the University Medical Centre of Utrecht, the Netherlands
BMCH, Chitradurga
Thank you