Rehabilitative Audiology

Hearing Aids - Sound Sidekicks

Amplify sound for hearing loss, aiding speech understanding & communication.

• Core Components:
  • Mic: Converts sound to electrical signal.
  • Amplifier: Increases signal strength.
  • Receiver: Delivers amplified sound to ear.
  • Battery: Powers HA; common type zinc-air.
• Common Types:
  • BTE (Behind-The-Ear): Powerful, versatile for various HL degrees.
  • RIC (Receiver-In-Canal): Discreet BTE style, natural sound quality.
  • Custom (ITE, ITC, CIC): Fit in ear/canal; CIC smallest, most discreet.
  • Bone Conduction: For conductive HL, atresia, SSD.
• Key Parameters:
  • Gain: Degree of sound amplification ($dB$).
  • OSPL90: Maximum sound output; prevents loudness discomfort.
• Selection: Based on audiogram, ear anatomy, patient dexterity, cosmetic preference.

⭐ Digital HAs use WDRC (Wide Dynamic Range Compression) to amplify soft sounds more than loud ones, improving speech clarity in noise.

Cochlear Implants - Inner Ear Heroes

Surgically implanted devices for severe-to-profound SNHL, bypassing damaged hair cells to stimulate the auditory nerve.

• Mechanism: Electrical stimulation of spiral ganglion neurons in cochlea.
• Key Indications:
  • Bilateral severe-to-profound SNHL (>70 dB HL).
  • Poor hearing aid benefit (<50% sentence score).
  • Age ≥9-12 months (congenital).
• Key Contraindications:
  • Central deafness.
  • Cochlear aplasia/ossification.
  • Active middle ear infection.
• Parts:
  • External: Microphone, Speech Processor, Transmitter.
  • Internal: Receiver-Stimulator, Electrode Array (in scala tympani).

⭐ High-Yield: Intensive post-operative auditory rehabilitation is VITAL for CI success, especially in prelingual children.

• 📌 Early implantation (<2 yrs for congenital deafness) yields better speech/language outcomes.

Other Implantables & ALDs - Niche Navigators

• Bone Anchored Hearing Aids (BAHA) / Bone Conduction Hearing Implants (BCHI):
  • Indications: Conductive HL (e.g., atresia, chronic suppurative otitis media), mixed HL, single-sided deafness (SSD).
  • Mechanism: Direct bone conduction, bypassing outer/middle ear.
• Middle Ear Implants (MEI):
  • Indications: Moderate-severe SNHL or mixed HL; for patients unable to use conventional HAs (e.g., chronic otitis externa, feedback).
  • Mechanism: Directly vibrates ossicles or round window. E.g., Vibrant Soundbridge.
• Auditory Brainstem Implant (ABI):
  • Indications: Neurofibromatosis type 2 (NF2) post-vestibular schwannoma excision, cochlear nerve aplasia.
  • Mechanism: Stimulates cochlear nucleus.

  ⭐ ABI is the only option for patients with bilateral cochlear nerve aplasia or transection, or complete cochlear ossification unsuitable for CI.

• Assistive Listening Devices (ALDs):
  • Purpose: Enhance signal-to-noise ratio (SNR); overcome distance, noise, reverberation.
  • Examples: FM systems, infrared systems, induction loops, alerting devices.

Aural Rehab & Counselling - Brain Rewiring

• Aural Rehabilitation (AR): Reduces hearing loss impact.
  • Focus: Improves auditory skills, communication, psychosocial well-being.
  • Methods: Auditory training, speech reading (lip-reading), communication strategy training.
• Counselling: Integral to AR.
  • Informational: Nature of hearing loss, device use, realistic outcomes.
  • Adjustment: Coping with emotional/social challenges.
• Brain Rewiring (Neuroplasticity): Brain adapts to altered auditory input.
  • Key to AR success with hearing aids/Cochlear Implants (CIs).
  • Enhanced by consistent device use & active listening exercises.

⭐ Auditory training programs are designed to harness neuroplasticity, enhancing the brain's ability to process and interpret amplified or new electrical (CI) sound signals.

High‑Yield Points - ⚡ Biggest Takeaways

• Cochlear Implants (CI): For bilateral severe-profound SNHL, bypassing damaged cochlear hair cells.
• Hearing Aids: Amplify sounds; BTE most versatile, CIC/IIC for best cosmetics.
• Auditory Brainstem Implants (ABI): Indicated for cochlear nerve aplasia/avulsion or after NF2 surgery.
• Newborn Hearing Screening: Uses OAE (screening) then BERA/ASSR (diagnostic) if failed.
• Bone Conduction Devices (BAHA/BCDs): For conductive loss (atresia, COM) or single-sided deafness (SSD).
• Aural Rehabilitation: Essential post-device fitting; includes auditory training, speech reading, counseling.