Basic Operation of Cochlear Implants, Brief Introduction, Histor Flashcards
1
Q
What is the significance of the Military Medical Academy in Leningrad in the 1930s?
A
- Stimulating electrodes inserted into the middle ear of patients with and without ME structures
- Frequency of alternating current (AC) was varied and patients asked to describe the pitch (Gersuni & Volokhov, 1936)
- Pitch was no different for patients with or without ME structures. so ME was ruled out as the site of electrical stim
2
Q
What is electrophonic hearing?
A
- Electrical stim of the organ of Corti causes mechanical response = release NTs from HCs onto nVIII
- Tectorial membrane converts electrical signal into the acoustic resulting in tonal pitch but at double the signal frequency
- Direct electric activation of nVIII with steep loudness growth and occasional activation of nVIII
3
Q
What is the cochlear microphonic?
A
- Electrical potentials measured primarily from OHCs in cochlea in response to stimulus
- Closely mirrored the stimulus
- Aka the Wever-Bray effect
- Used to dismiss the “telephone theory” of hearing
4
Q
What were conclusions about telephonic hearing?
A
- Research from late 40s and 50s concluded that deafness could not be completely corrected with wide-field electrical stimulation
- Instead, more localized summation of ANFs would be necessary
5
Q
What is the significance of Djourno and Eyries?
A
- Seminal work on direct auditory nerve stimulation with coil
- Djourno was a physiologist/researcher interested in neural prosthesis and Eyries was an otolaryngologist
- First subject was a 57-y/o man s/p bilateral cholesteatoma resection, which resulted in deafness and facial paralysis
- Surgery performed on 2/25/57
- Patient underwent extensive therapy and was able to discriminate intensity differences well (butt poor frequency perception and non-existent speech perception)
- Implant subsequently malfunctioned (twice) and Eyries and Djourno stopped working together but still credited with the first CI
6
Q
Who was William House, MD, DDS?
A
- Dentist-turned-otologist
- Patient brought in a French article about the work of Eyries and Djourno
- House has previously experimented with electrical hearing in patients during stapes surgery by placing electrodes on/near the oval window
- Collaborated with Doyle brother (a neurosurgeon and an electrical engineer) to create CI
7
Q
Who was F. Blair Simmons?
A
- Stanford research and otolaryngologist that conducted an intraoperative study in an 18 y/o patient (indicated bipolar stim of nVIII, yielded auditory sensations and discrimination of different stim frequencies)
- Two years later (1964), he implanted an electrical hearing device into the modiolus of a 60 y/o man
- F/up pyschological testing of the pt. was difficult and Simmons was pessimistic about future electrical stim of nVIII yielding useful speech information
8
Q
Who developed the first single-channel device?
A
- William House and electrical engineer Jack Urban
- House was concerned with safety and efficacy of the device
- One pt. became a long-term experimental subject
- From research on Graser, House & Urban abandoned the idea of multiple-electrode system and instead, went for single-wire electrode
9
Q
Who was Robin Michelson?
A
- Otolaryngologist in private practice who implanted several deaf patients with single-channel CIs in the 60s
- Found that pts. could discriminate among different stim rates up to 600 Hz and differentiate between square and sinusoid wave
- Partnered with Merzenich, a neurophysiologist, who was interested in mapping the IC
10
Q
What was the Bilger Report (1975)?
A
- 13 adult single-channel CI users (11 by House, 2 by Michelson) were studied in Pittsburgh
- First study that legitimized CI use
- Found that speech-reading scores were improved in all adults and that quality of life was significantly improved with minimal risk (still no open set speech recognition, but improved voice production)
11
Q
What is the House/3M device?
A
- 1972: House & Urban developed speech processor to accompany their single channel device (3M)
- Implanted approx. 1000 people with device between 1972 and 1980s
- Age criteria lowered from 18 years to 2 years of age in 1980
- Received FDA approval for commercial marketing of device in 1984
12
Q
What are the effects of deafness on the cochlea?
A
- Primary place of concern is SGNs
- More SGNs associated with better CI performance
- Survival of SGNs dependent on presence of sensory epithelium and support cells of OoC
- After loss of epithelium and support cells: 1) unmyelinated parts of SGNs in OoC degenerate rapidly, 2) more gradually, myelinated portions w/in osseous spiral lamina atrophy, 3) cell bodies in Rosenthal’s canal degenerate
- Finally, soma of SGNs demyelinate and perikaryon shrinks
- NOTE: Degeneration is an ongoing process
13
Q
Why does loss of HCs cause SGN degeneration?
A
- HCs and support cells in OoC are lost in SNHL
- HCs express neurotrophic factors
- Support cells express nerve growth factors
14
Q
What pathologies directly affect SGNS?
A
- Viral and bacterial labyrinthitis
- Mechanical traume
- Disruption of cochlear vasculature
^All result in more rapid degeneration of SGNs
15
Q
What etiologies result in most SGN loss?
A
- Postnatal viral labyrinthitis
- Congenital/genetic deafness
- Bacterial meningitis
