Effects of Skin Thickness on Cochlear Input Signal Using Transcutaneous Bone Conduction Implants. Issue 8 (September 2015)

• Record Type: Journal Article
• Authors: Mattingly, Jameson K.; Greene, Nathaniel T.; Jenkins, Herman A.; Tollin, Daniel J.; Easter, James R.; Cass, Stephen P.
• Is Part Of: Otology & neurotology. Volume 36:Issue 8(2015)
• Publication Date: 2015-09
• Subjects: Otology -- Periodicals; Ear -- Diseases -- Periodicals; Skull base -- Surgery -- Periodicals; 617.8005
• DOI: 10.1097/MAO.0000000000000814
• Languages: English
• ISSNs: 1531-7129

Abstract

<abstract> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <title>Hypothesis</title> <p>Intracochlear sound pressures (<italic>P</italic><sub>IC</sub>) and velocity measurements of the stapes, round window, and promontory (<italic>V</italic><sub>Stap/RW/Prom</sub>) will show frequency-dependent attenuation using magnet-based transcutaneous bone conduction implants (TCBCIs) in comparison with direct-connect skin-penetrating implants (DCBCIs).</p> </sec> <sec> <title>Background</title> <p>TCBCIs have recently been introduced as alternatives to DCBCIs. Clinical studies have demonstrated elevated high-frequency thresholds for TCBCIs as compared with DCBCIs; however, little data exist examining the direct effect of skin thickness on the cochlear input signal using TCBCIs.</p> </sec> <sec> <title>Methods</title> <p>Using seven cadaveric heads, <italic>P</italic><sub>IC</sub> was measured in the scala vestibuli and tympani with fiber-optic pressure sensors concurrently with <italic>V</italic><sub>Stap/RW/Prom</sub> via laser Doppler vibrometry. Ipsilateral titanium implant fixtures were placed and connected to either a DCBCI or a TCBCI. Soft tissue flaps with varying thicknesses (no flap and 3, 6, and 9 mm) were placed successively between the magnetic plate and sound processor magnet. A bone conduction transducer coupled to custom software provided pure-tone stimuli between 120 and 10, 240 Hz.</p> </sec> <sec> <title>Results</title> <p>Stimulation via the DCBCI produced the largest response magnitudes. The TCBCI showed similar <italic>P</italic><sub>SV/ST</sub> and <italic>V</italic><sub>Stap/RW/Prom</sub> with no intervening flap and a frequency-dependent nonlinear reduction of magnitude with increasing flap thickness. Phase shows a comparable dependence on transmission delay as the acoustic baseline, and the slope steepens at higher frequencies as flap thickness increases, suggesting a longer group delay.</p> </sec> <sec> <title>Conclusion</title> <p>Proper soft tissue management is critical to optimize the cochlear input signal. The skin thickness–related effects on cochlear response magnitudes should be taken into account when selecting patients for a TCBCI.</p> </sec> </abstract>