Experimental investigation of promontory motion and intracranial pressure following bone conduction: Stimulation site and coupling type dependence

Abstract

Objective Investigation of bone conduction sound propagation by osseous and non-osseous pathways and their interactions based upon the stimulation site and coupling method of the actuator from a bone conduction hearing aid (BCHA). Methods Experiments were conducted on five Thiel embalmed whole head cadaver specimens. The electromagnetic actuator from a commercial bone conduction hearing aid (BCHA) (Baha® Cordelle II) was used to provide a stepped sine stimulus in the range of 0.1-10 kHz. Osseous pathways (direct bone stimulation or transcutaneous stimulation) were sequentially activated by stimulation at the mastoid or the BAHA side using several methods including a percutaneously implanted screw, Baha® Attract transcutaneous magnet and a 5-N (5-N) steel headband. Non-osseous pathways (only soft tissue or intra-cranial contents) were activated by actuator stimulation on the eye or neck via attachment to a 5-N steel headband, and were compared with stimulation via equivalent attachment on the mastoid and forehead. The response of the skull was measured as motions of the ipsi-and contralateral promontory and intracranial pressure (ICP) in the central, anterior, posterior, ipsilateral and contralateral temporal regions of the cranial space. Promontory motion was monitored using a 3-dimensional Laser Doppler vibrometer (3D LDV) system. Results The promontory undergoes spatially complex motion with similar contributions from all motion components, regardless of stimulation mode. Combined 3D promontory motion provided lower inter-sample variability than did any individual component. Transcranial transmission showed gain for the low frequencies and attenuation above 1 kHz, independent of stimulation mode This effect was not only for the magnitude but also its spatial composition such that contralateral promontory motion did not follow the direction of ipsilateral stimulation above 0.5 kHz. Non-osseous stimulation on the neck and eye induced comparable ICP relative to percutaneous (via screw) mastoid stimulation. Corresponding phase data indicated lower phase delays for ICP when stimulation was via non-osseous means (i.e., to the eye) versus osseous means (i.e., to the mastoid or forehead). Sound propagation due to skull stimulation passes through the thicker bony sections first before activating the CSF. Conclusion Utilization of 3D promontory motion measurements provides more precise (lower inter-sample variability) information about bone vibrations than does any individual component. It also provides a more detailed description of transcranial attenuation. A comprehensive combination of motion and pressures measurements across the head, combined with a variation of the stimulation condition, could reveal details about sound transmission within the skull. Abstract ObjectivesInvestigation of bone conduction sound propagation by osseous and non-osseous pathways and their interactions based upon the stimulation site and coupling method of the actuator from a bone conduction hearing aid (BCHA). MethodsExperiments were cond...

Bone-conduction hyperacusis induced by superior canal dehiscence in human: the underlying mechanism

“…This pathway is thought to be a possible cause of certain SCD-induced symptoms of BC hyperacusis, such as hearing one’s eyeballs move 7 . Although the present study shows that BC can be increased by SCD in isolated temporal bones, BC-induced sound pressures within the cranium of the whole head 33 may lead to additional sound transmission from the cranium to the inner ear via SCD and thus further enhance BC. To model this intra-cranial sound conducting mechanism, a sound pressure source representing the sound in the skull may be added atop the SCD in Fig.…”

“…Another possible mechanism to explain BC is that sound can be transmitted from the contents of the skull—brain, dura, and cerebrospinal fluid (CSF)—to the inner ear via conducting channels such as aqueducts, nerves, and vasculature 31 – 33 . With SCD, the BC sound produced in the cranial tissues within the skull may be transmitted to the inner ear directly through the dehiscence.…”

Effectiveness of Bone Conduction Stimulation Applied Directly to the Otic Capsule Measured at Promontory: Assessment in Cadavers

“…[2000] showed that the labyrinth of an intact skull subjected to BC vibrates in all 3 planes without any of them dominating. Recently, Dobrev et al [2019] measured the 3D motion of the promontory using a system based on a commercial 3-dimensional laser Doppler vibrometer (3D LDV). In their study, the authors concluded that recording the 3D promontory motion provides more data about bone vibrations than any individual component does.…”

Experimentelle Evaluation des Adhear, eines neuen transkutanen Knochenleitungshörgeräts

“…1). Der Aufbau und die Messungen erfolgten wie zuvor ausführlich beschrieben [12][13][14]. Es wurde die 3-dimensionale (3D) Vibration des ipsilateralen und kontralateralen Promontoriums mit dem Single-point-3D-Laser-Doppler-Vibrometer (LDV) (3D CLV 3000, Polytec GmbH, Deutschland) gemessen, der an einem Roboterarm (KR 16, KUKA, Deutschland) fixiert war.…”

“…Die Vibrationen des ipsi-und kontralateralen Promontoriums wurden gemessen, da diese eine Annäherung der Hörschwelle sind [21]. Dabei wurde darauf geachtet, dass derselbe Stimulationsort gewählt wurde, da dieser einen Einfluss auf die Stimulationseffizienz hat [13]. Die Ergebnisse konnten mit früheren Messungen mit dem Baha Power am 5N-Stahlband verglichen werden [13] und zeigten keine großen Differenzen.…”