Enduring Long-Term Speech Comprehension Benefits of Apical Stimulation in Cochlear Implantation

Transcription

1 Enduring Long-Term Speech Comprehension Benefits of Apical Stimulation in Cochlear Implantation Kevin D. Brown, Meg Dillon, Meredith Anderson, Ellen Pearce, English King, Craig Buchman and Harold C. Pillsbury Department of Otolaryngology Head and Neck Surgery University of North Carolina

2 Disclosures Research support from all 3 cochlear implant companies

3 Why Interest in Apical Stimulation? EAS data suggests multiple benefits of low frequency acoustic hearing such as 1. Music perception 2. Improved Pitch perception 3. * Improved speech understanding (in noise) 4. QOL Can this effect be reproduced electrically?

4 Can Apical CI simulate Low Frequency Benefits? First question is if there is sufficient neural tissue to carry information of cochlear implant Spoendlin et al 1988 spiral ganglia neurons only extend over the first 1½ turns of cochlea Hamzavi et al, Hochmair et al demonstrated significant improvements in speech understanding when apical electrodes where stimulated compared to basal electrodes alone Suggests cochlea responds to low frequency information delivered from apical electrodes and that it is critical to improved CI function

5 Low Frequency Coding Schatzer et al 2014 demonstrated using SSD patients that the acoustic pitch produced by low frequency pure tones can be best matched by stimulating electrodes in second turn of cochlea at rate = pure tone This required electrodes be apical in location to produce this effect What is counter-argument to apical electrodes

6 Cortical Frequency Mapping Over time cortex can adapt to frequency mismatch Reiss et al 2014 Plasticity in human pitch perception with place coding Change can be up to 3 octaves difference Suggests cortical plasticity permits subjects with non-apical electrodes to catch up over time

7 Question Do patients with incomplete apical coverage of the cochlea do as well as those with complete coverage over time?

8 Methods Randomized prospective trial comparing standard CI patients receiving either of two lateral wall electrodes (Buchman et al 1. Medium array = 24mm with contacts spread over 20.9mm 2. Standard array = 31mm with contacts over 26.4mm

9 Methods Average depth of insertion 1. Standard array = mean 657 degrees ( ) 2. Medium Array = mean 423 degrees ( ) Followed patients prospectively and measured speech outcomes (CNC and HINT testing)

10 Previous Data Buchman et al Study was halted after 13 patients were enrolled by institutional IRB due to clinically significant differences between treatment outcomes between groups An additional six standard array recipients that met study criteria were then enrolled retrospectively to permit greater power in the analysis

11 Prior Results CNC HINT10

12 Does Difference Persist? Continued to test patients out to 2 years following implantation for speech scores Wished to determine if differences between standard and medium electrodes persisted Were subjects able to accommodate to lack of apical simulation over time?

13 CNC Results CNC Results * Medium Array Standard Array CNC% Pre 3 mos 6 mos 12 mos 24 mos Time Elapsed

14 CNC Individual Results CNC Results * Standard Array Medium Array CNC% Pre 3 mos 6 mos 12 mos 24 mos Time Elapsed

15 HINT10 Results HINT10 Results * * * Medium Array Standard Array HINT10% Pre 3 mos 6 mos 12 mos 24 mos Time Elapsed

16 HINT10 Individual Results HINT10 Results * * * Standard Array Medium Array HINT10% Pre 3 mos 6 mos 12 mos 24 mos Time Elapsed

17 Conclusions When keeping electrode size, design (lateral wall), and processing strategy constant 1. Greater depth of cochlear implant electrode insertion affords better speech performance outcomes that persist out to 2 years following implantation when using the same implant system. 2. Suggests that accommodation and cortical plasticity can not always overcome frequency mismatch in cochlea

18 Further Considerations Cognitive capacity likely plays role in ability of patient to accommodate to frequency mismatch As such older adult patients with potentially less plasticity and cognitive capacity may be more strongly indicated for deep electrode placement to provide apical stimulation, ameliorating the need for cortical plasticity