1. Imaging such as HRCT and MRI are important for evaluating patients for cochlear implantation to identify any contraindications and guide surgery. HRCT is useful for evaluating bony anatomy while MRI can identify soft tissue anomalies.
2. Pre-operative imaging aims to evaluate factors like the size of the internal auditory meatus, status of the cochlear nerve, and presence of any neurovascular anomalies which could increase surgical risk. Anomalies of the bony and membranous labyrinth are also assessed.
3. Congenital anomalies identified on imaging can help determine the cause of hearing loss and surgical approach during cochlear implantation.
Glomerular Filtration and determinants of glomerular filtration .pptx
Imaging requirements for cochlear implantation
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
2. 4/16/2013 24/16/2013 2BMCH, Chitradurga
• Determine patients with
Contraindications for CI
• Determine the approach
• As a guide during surgery
Why Imaging?
Objectives
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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
5. 4/16/2013 54/16/2013 5BMCH, Chitradurga
• 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
6. 4/16/2013 64/16/2013 6BMCH, Chitradurga
• CT demonstrates anomalies of the bony
labyrinth such as
– Paget’s disease
– Otosclerosis
– Postmeningitis stenosis of the round
window niche.
Role of HRCT
Protocol
7. 4/16/2013 74/16/2013 7BMCH, Chitradurga
• 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
11. 4/16/2013 114/16/2013 11BMCH, Chitradurga
• 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. 4/16/2013 124/16/2013 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
15. BMCH, Chitradurga
MRI - Constructive Interference
Steady State (CISS)
Science Photo library
Advantage : Combination of high signal levels and
extremely high spatial resolution.
16. 4/16/2013 164/16/2013 16BMCH, Chitradurga
• 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
17. 4/16/2013 174/16/2013 17BMCH, Chitradurga
• 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
18. 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 patients
are more difficult to obtain, as difficulties of
communication may lead to movement
artefacts.
– Sedation is needed in children.
HRCT Vs MRI
Protocol
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
37. 4/16/2013 374/16/2013 37BMCH, 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 IAM
KeyPoints
38. 4/16/2013 384/16/2013 38BMCH, 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 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
42. 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 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. 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 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. 4/16/2013 464/16/2013 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
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
54. 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 anomalies
Classification
Sennaroglu L, Saatci I. Laryngoscope. 2002;112:2230–41.
55. 4/16/2013 554/16/2013 55BMCH, 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.
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.
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.
62. 4/16/2013 624/16/2013 62BMCH, 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.
mplete partition of Cochlea
Classification
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.
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 – 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
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
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.