Cochlear implant operation

1. Cochlear implant
Dr Dalia El Saied, MD
Radiodiagnosis Lecturer at General Organization for Teaching Hospitals and
Institutes.

2. Anatomy (Axial images)

3. Anatomy (Axial images)

4. Anatomy (Coronal images)

5. Anatomy (Coronal images)

6.  External components
 Internal components
Implant components

7. Profound to severe and
bilateral sensorineural
hearing impairment.
Indication

8. Mechanism of action
The implant converts
the coded signal into
electrical signal and
sends it to the electrodes
located in the cochlea,
that stimulate the
remaining cells of the
organ of Corti. Then the
impulse travels normally
through the rest of the
auditory pathway.
Sound Microphone
Amplifier
Sound coding Cochlear electrodes
Transmission to implant

9. Procedure
 Mastoidectomy .
 Posterior tympanotomy
using the facial recess (FR)
as a route of access.
 Electrode insertion into the
scala tympani either through
cochleostomy or through
round window.

10. Point of cochleostomy
Contacts

11. To obtain MPR : slices taken parallel to cochlea basal turn and perpendicular to the
modiolus
and second set of slices perpendicular to the cochlea basal turn and parallel to the
modiolus rendering coronal images of the scala tympani and vestibuli.
CT images and MPR

12. Role of radiologists
 Preoperative assessment:- for patient selection for
surgery.
 Postoperative :- for correct position of the device and the
presence of complications.

13. • Absence of cochlear nerve.
• Cochlear agenesis.
Absolute
contraindications
• Cochlear aplasia, labyrinthine aplasia, Severe
hypoplasia,
• IAM abnormalities associated with cochlear nerve
agenesis.
Surgical
contraindications
• Schwannoma, brainstem ischemia, secondary
hemosiderosis after subarachnoid hemorrhage.Other Situations
Patient selection

14. Normal cochlear nerve

15. Cochlear nerve agenesis.

16. Cochlear nerve deficiency.
Hypoplastic IAM with single nerve
extending from the cistern into IAM
Normally two nerves are
seen within the IAM.

17. Cochlear hypoplasia.

18. Incomplete partition cochlear malformation
(Type I)
Dilated cystic appearing cochlea (red arrows), Dilated vestibule(yellow arrows) and Dilated
Internal Auditory Canal (blue arrow),

19. Mondini Malformation (Incomplete
partition type II)
Cystic cochlear apex (red arrows) with no differentiation of the apical and second
turns. A grossly enlarged vestibular aqueduct (yellow arrows)

20. Labyrinthitis ossificans

21. Fenestral otosclerosis
and cochlear otosclerosis (Halo sign)

22. Bilateral enlargement of endolymphatic ducts

23. Hypoplastic mastoid process

24. Normal versus sclerosed mastoid

25. Petrous apex changes

26. Dehiscent jugular bulb

27. Preoperative assessment
Cochlear nerve
Normal
Hypoplasia
Agenesis
Cochlea
Normal
Malformation (Hypoplasia,
incomplete partition, common cavity, aplasia)
Ossification: localization,
extension, fibrosis, yes/no
Other
Fracture, tumor,
haemosidrin deposits,
ischemic lesions of
pons…..
Middle ear
Neurovascular anatomy and
variations
Otosclerosis,: yes/no
Mastoid bone
Size
Pneumatization
Sclerosis
occupation
Round window
Normal. Size
Vestibular Aqueduct
Normal or enlarged

28. *** CT is done for:-
 Assessment of electrode placement.
 Suspected complications.
Post operative assessment

29. 1- Electrode placement
Appearance of the electrode.
 The position of the electrode.
Insertion in depth: done by counting the number of electrodes which pass
through the cochlea. The deeper, the electrodes are (closer to the apical turn
of the cochlea) the greater auditory recovery is.
Angular insertion: is the angle that the electrode forms with the cochlea

30. Electrode position.
Complete insertion of the electrodes is when all
are medial to the line of the cochleostomy.
Incomplete insertion is when one or more
electrodes do not pass through the cochleostomy.
The 12th electrode is the nearer to the round window and the 1th one is in
the apex.

31. The ectrode array is designed to place the stimulating contacts in close proximity to the spiral ganglion cells
located within the modiolus.
Postoperative documentation of the precise location of individual electrode contacts in relation to the
modiolus.
Location
There is a large gap between the contacts and
the modiolus (lines)

32. 2- Complications
• Infections.
Early
• Mastoiditis.
• Facial nerve stimulation
• Malfunction of the implant: warning
signs are severe pain and tinnitus.
Delayed

33. Post operative changes
Opacification of the left
mastoid and tympanic cavity
regions, with a focal alteration
of the frontal osseous cortical
outline (arrow).
Another patient shows complete
left cochlear ossification (arrow)
and increased attenuation of
tympanic cavity.

34. Preoperative
Post operative
Summary

36.  Cochlear nerve (MRI).
 Cochlear ducts abnormalities.
 Mastoid process.
 Facial recess and sinus tympani.
 Facial nerve canal.
 Round window.
 Vestibular abnormalities.
 Length and width of IAM.
 Jugular bulb variations:-
e.g:- dehiscent jugular bulb.
Important points in the preoperative report
Round windowFacial nerve Facial recess

37.  Adequate positioning of the electrode array. (Complete Vs
incomplete insertion).
 Operative bed complications.
Important points in the postoperative report

38. Thank you