ABA Cochlear Implants & Implantable Hearing Devices 2 — Questions and Answers
Question 1: Which imaging study is most commonly ordered prior to cochlear implant surgery to evaluate cochlear anatomy and patency?
- Plain X-ray of the mastoid
- Computed tomography (CT) of the temporal bones (Correct answer)
- Positron emission tomography (PET) scan
- Brainstem auditory evoked response (BAER)
Correct answer: Computed tomography (CT) of the temporal bones
High-resolution CT of the temporal bones is the standard pre-operative imaging to assess cochlear anatomy, detect ossification, malformations, and surgical landmarks.
Question 2: In CI programming, the 'C-level' (comfort level or MCL) represents:
- The level associated with the acoustic reflex threshold
- The loudest comfortable level of electrical stimulation before discomfort (Correct answer)
- The center frequency of the processing channel
- The current level at which the device switches processing strategies
Correct answer: The loudest comfortable level of electrical stimulation before discomfort
The C-level (also called MCL or M-level) is the maximum comfortable loudness level — the highest electrical stimulation that is loud but not uncomfortable for the CI user.
Question 3: Which cochlear implant processing strategy uses a 'n-of-m' approach where only the channels with the highest amplitude outputs are stimulated each cycle?
- Continuous Interleaved Sampling (CIS)
- Spectral Peak (SPEAK)
- Advanced Combination Encoder (ACE) (Correct answer)
- Analog Simultaneous Stimulation (ASS)
Correct answer: Advanced Combination Encoder (ACE)
ACE (Advanced Combination Encoder) selects the n channels with the greatest energy from a bank of m filters each cycle, providing a balance between spectral and temporal information.
Question 4: Electrode impedance checks in CI programming primarily assess:
- The frequency resolution of the cochlear implant
- The integrity of the electrical circuit between the electrode and the tissue interface (Correct answer)
- The signal-to-noise ratio of the internal microphone
- The battery life remaining in the external processor
Correct answer: The integrity of the electrical circuit between the electrode and the tissue interface
Impedance measurements evaluate the integrity of the electrode–tissue interface; abnormally high impedances may indicate an open circuit, and very low impedances can indicate a short circuit.
Question 5: A child receives a cochlear implant at age 18 months. According to research on critical periods, when should auditory rehabilitation be most intensively initiated?
- After the child reaches kindergarten age
- Immediately following device activation (Correct answer)
- Only after the child demonstrates plateau in aided performance
- At age 3 when language develops more rapidly
Correct answer: Immediately following device activation
Auditory rehabilitation should begin immediately at device activation to take advantage of the sensitive period for auditory cortical development and maximize speech/language outcomes.
Question 6: What does 'stapedius reflex threshold' measurement provide in the context of cochlear implant programming?
- A direct measure of speech intelligibility with the CI
- An objective way to estimate C-levels by detecting the reflexive middle ear muscle contraction (Correct answer)
- Verification that the CI is transmitting signal to the brainstem
- Measurement of electrode insertion depth
Correct answer: An objective way to estimate C-levels by detecting the reflexive middle ear muscle contraction
Electrically evoked stapedial reflex thresholds (ESRT) can serve as objective landmarks for setting C-levels, as the reflex typically occurs near the upper end of the comfortable range.
Question 7: Bilateral cochlear implantation is most supported by evidence for which outcome benefit?
- Improved tonal music appreciation
- Enhanced sound localization and speech understanding in noise (Correct answer)
- Elimination of phantom auditory percepts (tinnitus)
- Reduction in vestibular side effects
Correct answer: Enhanced sound localization and speech understanding in noise
Bilateral CI provides binaural hearing, which significantly improves sound source localization and speech understanding in background noise compared to unilateral implantation.
ABA Cochlear Implants & Implantable Hearing Devices 2
Which imaging study is most commonly ordered prior to cochlear implant surgery to evaluate cochlear anatomy and patency?