Cochlear implant imaging

1. BMCH, Chitradurga
Imaging Requirements for
Cochlear Implantation
Dr. Prahlada N.B
MBBS, MS, MBA, MHA
ENT, HEAD – NECK & SKULL BASE SURGERY
Basaveshwara Medical College & Hospital
Chitradurga

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• Determine patients with
Contraindications for CI
• Determine the approach
• As a guide during surgery
Why Imaging?
Objectives

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• HRCT temporal bone.
• MRI
What type of Imaging
Protocol

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• Evaluates the status of
– Mastoid pneumatisation
– Thickness of the cortical bone
– Middle ear aeration
– The round window niche
Role of HRCT
Protocol

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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 HRCT
Protocol

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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 HRCT
Protocol

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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
HRCT
Protocol

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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.
HRCT
Protocol

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• Coronal reformations along with 3D
maximum intensity projection (MIP)
reconstructions.
HRCT
Protocol

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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 MRI
Protocol

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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
MRI
Protocol

12. 10-04-2017 1210-04-2017 12BMCH, Chitradurga
• 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.
MRI
Protocol

13. BMCH, Chitradurga
MRI Direct Oblique Saggittal View
Cadaver Dissection showing Direct Oblique Sagittal View.

14. BMCH, Chitradurga
MRI Direct Oblique Saggittal View

15. BMCH, Chitradurga
MRI - Constructive Interference
Steady State (CISS)
Science Photo library
Advantage : Combination of high signal levels and
extremely 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.
MRI
Protocol

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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 MRI
Protocol

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• 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 MRI
Protocol

19. BMCH, Chitradurga
NORMAL ANATOMY - HRCT
Imaging requirements for Cochlear Implantation

20. 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

21. 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

22. 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 meatus
15 Aditus to mastoid antrum 16 Vestibule 17 Posterior semicircular canal 18 Mastoid antrum 19 Lateral semicircular canal
Frontal
Medial
Occipital
Lateral

23. 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 meatus
15 Aditus to mastoid antrum 16 Vestibule 17 Posterior semicircular canal 18 Mastoid antrum 19 Lateral semicircular canal
Frontal
Medial
Occipital
Lateral

24. BMCH, Chitradurga
1 Geniculate ganglion 2 Facial nerve (first part) 3 Facial nerve (second part) 4 Internal acoustic meatus 5 Tympanic cavity
6 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

25. 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 cavity
6 Vestibule 7 Posterior semicircular canal 8 Mastoid antrum 9 Lateral semicircular canal 10 Sigmoid sinus 11 Anterior (superior)
semicircular canal 12 Mastoid cells

26. BMCH, Chitradurga
NORMAL ANATOMY - MRI
Imaging requirements for Cochlear Implantation.

27. BMCH, Chitradurga

28. BMCH, Chitradurga

29. BMCH, Chitradurga

30. BMCH, Chitradurga

31. BMCH, Chitradurga

32. BMCH, Chitradurga

33. BMCH, Chitradurga

34. BMCH, Chitradurga
Inferior view of 3D maximum intensity
projection (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

35. 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

36. BMCH, Chitradurga
PRE-SURGICAL EVALUATION
Imaging requirements for Cochlear Implantation

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• 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 IAM
KeyPoints

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• 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 status
KeyPoints

39. BMCH, Chitradurga
Modiolus
The 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

40. BMCH, Chitradurga
Cochlear nerve deficiency
C. Isolated Cochlea. D. Absent Cochlear Nerve.
Christine M. Imaging Findings of Cochlear Nerve Deficiency. AJNR 2002 23: 635-643

41. BMCH, Chitradurga
Absent Modiolus
Axial 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

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• Anomaly of the course of the:
• Facial nerve
• The carotid artery
• The sigmoid sinus
• Venous variants such mastoid emissary
veins
2. Neurovascular Anomaly
KeyPoints

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• 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 Anomaly
KeyPoints

44. 10-04-2017 4410-04-2017 44BMCH, Chitradurga
• Study:
– The number of cochlear turns
– Symmetry of scala chambers
– Status of the modiolus
– Status of the posterior membranous
labyrinth.
mbranous labyrinth anomaly
KeyPoints

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• 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
KeyPoints

46. 10-04-2017 4610-04-2017 46BMCH, 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.
ndo- and perilymphatic fluid
Status
KeyPoints

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• Stenosis of the round window niche may
occur in bone remodelling lesions such
as:
– Paget’s disease
– Otosclerosis
– Lobstein disease
– Post-meningitis labyrinthitis.
Status of Bony Labyrinth &
Round Window Niche
KeyPoints

48. BMCH, Chitradurga
Paget’s Disease
Axial 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

49. BMCH, Chitradurga
Otosclerosis
Fenestral otosclerosis showing a fissula ad fenestram.
Medical Observer. Australia

50. BMCH, Chitradurga
Osteogenesis Imperfecta
The 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 Syndrome
Hatem Alkadhi . AJNR 2004 25: 1106-1109

51. 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

52. BMCH, Chitradurga
CONGENITAL ANOMALIES
Imaging requirements for Cochlear Implantation

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• Cochlear
• Vestibular
• Semicircular canal,
• Internal auditory canal (IAC)
• Vestibular and
• Cochlear aqueduct malformations.
Types of anomalies
Classification
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.

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• Michel deformity
• Common cavity deformity
• Cochlear aplasia
• Hypoplastic cochlea
• Incomplete partition types
– I (IP-I) and
– II (IP-II) (Mondini deformity).
Cochlear anomalies
Classification
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.

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• 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.
mplete partition of Cochlea
Classification
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.

56. 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.

57. BMCH, Chitradurga
Common cystic cavity
University of Washington Department of Radiology.

58. BMCH, Chitradurga
Incomplete partition - II
Classic Mondini malformation
University of Washington Department of Radiology.

59. BMCH, Chitradurga
Incomplete partition - II
Classic Mondini malformation
University of Washington Department of Radiology.

60. BMCH, Chitradurga
Incomplete partition variant
Normal basal turn of the Cochlear and Round Window
University of Washington Department of Radiology.

61. 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.

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• 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.
mplete partition of Cochlea
Classification

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• Michel deformity
• Cochlear aplasia
• Common cavity
• Cochlear hypoplasia
• IP-I (Cystic cochleovestibular
malformation),
• IP-II (Mondini deformity)
Clinical Classification
Classification
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.

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• Absent Cochlear nerve
– Diameter of IAM (mid-part) <3 mm
• Absent Cochlear
• Absent Modiulus
Contraindications for CI
NotoCI

65. 10-04-2017 6510-04-2017 65BMCH, 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
NotoCI

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• 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
NotoCI

67. BMCH, Chitradurga
Deficient Modiolus
Axial 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
,

68. BMCH, Chitradurga
Deficient Modiolus
Axial 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
,

69. BMCH, Chitradurga
Otosclerosis of the Cochlea
During 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

70. 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.

71. BMCH, Chitradurga
Semicircular Canal dilatation
There is a widening and shortening of the lateral semicircular
canal.
Eric Beek and Frank Pameijer: Temporal Bone Pathology.

72. BMCH, Chitradurga
Vestibular dilatation
The vestibule is relatively large (arrow).
Eric Beek and Frank Pameijer: Temporal Bone Pathology.

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• 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
NotoCI

74. BMCH, Chitradurga
Hypoplastic Mastoid Process
Right side, the mastoid air cells are under pneumatized. There is
no identifiable external auditory canal.
American College of Radiology

75. BMCH, Chitradurga
Normal Vs Sclerosed Mastoid
First: Normal pneumatized mastoid with aerated cells. The mastoid
is completely sclerotic - no air cells are present.

76. BMCH, Chitradurga
Chronic Otitis Media
The 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.

77. BMCH, Chitradurga
Dehiscent Facial Nerve
Robert J. Witte, MD: Pediatric and Adult Cochlear Implantation: RadioGraphics 2003; 23:1185–1200

78. BMCH, Chitradurga
Dehiscent Facial Nerve
Patient 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.

79. BMCH, Chitradurga
Mastoid Emissary Vein
H Alsherhri1, B Alqahtani2, M Alqahtani3: Year : 2011 | Volume : 17 | Issue : 3 | Page : 123-126

80. BMCH, Chitradurga
Anterior Bulging Sigmoid Sinus
The sigmoid sinus can protrude into the posterior mastoid.
It can be accidentally lacerated during a mastoidectomy .
Temporal bone – Pathology: Eric Beek and Frank Pameijer
Radiology department of the University Medical Centre of Utrecht, the Netherlands

81. BMCH, Chitradurga
High Jugular Bulb
The 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 Pameijer
Radiology department of the University Medical Centre of Utrecht, the Netherlands

82. BMCH, Chitradurga
Jugular Bulb Diverticulum
Rarely an out-pouching is seen &#8211; this is known as a jugular
bulb diverticulum.
Temporal bone – Pathology: Eric Beek and Frank Pameijer
Radiology department of the University Medical Centre of Utrecht, the Netherlands

83. BMCH, Chitradurga
Dehiscent jugular bulb
On 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 Pameijer
Radiology department of the University Medical Centre of Utrecht, the Netherlands

84. BMCH, Chitradurga
Persistent Stapedial Artery
www.neuroangio.org

85. BMCH, Chitradurga
Aberrant internal carotid artery
In 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 Pameijer
Radiology department of the University Medical Centre of Utrecht, the Netherlands

86. BMCH, Chitradurga
Aberrant internal carotid artery
On 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 Pameijer
Radiology department of the University Medical Centre of Utrecht, the Netherlands

87. BMCH, Chitradurga
Thank you