Cochlear Implants
Useful in Severe to Profound Sensorineural Hearing Loss With Severe Degeneration Of Hair Cell Of Cochlea where Hearing Aids Are ineffective
2 Component
External
Internal
Speech Processor + Transmitter
Receiver / Stimulater With Electrode array
Principle / Mechanism
Speech Sound ➡️ Speech Processor ➡️ Coding of Sound into Electrical impulses ( Radiofrequency Waves )
Various Coding Strategies ➡️
1.Simultaneous analogue strategy (SAS)
2.Spectral Speak (SPEAK)
3.Advanced Combination Encoder (ACE)
Radifreuency waves ➡️ Transmitter Coil ➡️ Receiver / Stimulator ➡️ Linear erray of Electrodes placed in Scala Tympanic Of Cochlea
Stimulates Spiral Ganglion Cells ➡️ Stimulation of Auditory Nerve ➡️ Processed in Brain 🧠
Candidacy Profile
(Both Childdren & Adults )
Bilateral Severe to Profound Sensorineural Hearing
Loss
No medical contraindications to surgery
Family & Social Support
Adequate Cognitive Function
Prelingual ( Early indicated for proper speech development) & Postlingual Sensorineural Deafness
FACTORS that determine
Successful outcome of Implantation
Postlingual Deafness
Previous Use Of Hearing Aids
Neural Plasticity within Auditory system
Younger age of Children ( Prelingual Deafness)
Clinical Evaluation before Implantation
Vaccination against Meningitis ( H Influenzae , Pneumococcus & Meningococcus )
CT Scan & MRI for Evaluation Of
Anatomy of Temporal bone , Cochlea & Auditory Nerve
Audio logical Evaluation
Pure Tone Audiogram
SD Score
Tympanometry
Otoacoustic Emissions ( OAE)
Auditory Brainstem Responses (ABR)
Auditory Steady state Responses ( ASSR)
Hearing Aid Trial & Evaluation
Speech & Language Evaluation
Useful in Programming Of Implantable Device
Psychological Evaluationfor Cognitive status Of Patient & Counseling Of Parents
Surgery
For Placing the Electrode array
in close proximity with Spiral Ganglion cells & Dendrites
2 Surgical Approach
FACIAL RECESS Approach
1.Cortical Mastoidectomy
- Posterior Tympanotomy ➡️ Facial Recess is Opened
- Cochleostomy( Diameter 1 to 1.6 mm) anteroinferior to the Round window Membrane
PERICANAL Approach
1.Elevation Of Tympanomeatal Flap ( Veria or Suprameatal Approach )
- Cochleostomy ( Endaural or Postaural Approach)
Electrophysiological Testing Of Implant should be done before complete the surgery
Postoperative Care
Postoperative Mapping ( Programmimg Of Device ) After 3 -4 Weeks Of implantation.
Rehabilitation
Auditory-Verbal Therapy
Example
MED-EL , Nucleus &
Advanced Bionics Cochlear Implants