Comparing Distortion Product Otoacoustic Emissions to Intracochlear Distortion Products Inferred from a Noninvasive Assay

Abstract

The behavior of intracochlear distortion products (iDPs) was inferred by interacting a probe tone (f₃) with the iDP of interest to produce a “secondary” distortion product otoacoustic emission termed DPOAE^2ry. Measures of the DPOAE^2ry were then used to deduce the properties of the iDP. This approach was used in alert rabbits and anesthetized gerbils to compare ear-canal 2f₁-f₂ and 2f₂-f₁ DPOAE f₂/f₁ ratio functions, level/phase (L/P) maps, and interference-response areas (IRAs) to their simultaneously collected DPOAE^2ry counterparts. These same measures were also collected in a human volunteer to demonstrate similarities with their laboratory animal counterparts and their potential applicability to humans. Results showed that DPOAEs and inferred iDPs evidenced distinct behaviors and properties. That is, DPOAE ratio functions elicited by low-level primaries peaked around an f₂/f₁ = 1.21 or 1.25, depending on species, while the corresponding inferred iDP ratio functions peaked at f₂/f₁ ratios of ~1. Additionally, L/P maps showed rapid phase variation with DPOAE frequency (f_dp) for the narrow-ratio 2f₁-f₂ and all 2f₂-f₁ DPOAEs, while the corresponding DPOAE^2ry measures evidenced relatively constant phases. Common features of narrow-ratio DPOAE IRAs, such as large enhancements for interference tones (ITs) presented above f₂, were not present in DPOAE^2ry IRAs. Finally, based on prior experiments in gerbils, the behavior of the iDP directly measured in intracochlear pressure was compared to the iDP inferred from the DPOAE^2ry and found to be similar. Together, these findings are consistent with the notion that under certain conditions, ear-canal DPOAEs provide poor representations of iDPs and thus support a “beamforming” hypothesis. According to this concept, distributed emission components directed toward the ear canal from the f₂ and basal to f₂ regions can be of differing phases and thus cancel, while these same components directed toward f_dp add in phase.

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Clinical Verification of Ear Level FM Systems: Classroom & Personal Use Applications

Dave Smriga: In today’s course, we’ll explore how Audioscan equipment easily facilitates the execution of the most current recommended FM verification procedures. In addition, we’ll discuss how you can use these procedures for both FM system verification and verification of remote microphone technology. Although we will be depicting the various test procedures included in today's webinar with images created using the Verifit2 hearing instrument fitting system, the same tests can be performed with the original Verifit system.

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The Ponto Bone Anchored System: The Right Choice for Pediatrics

Today, I will begin with the fundamentals of bone anchored technology including an overview of osseointegration, and that will give us the foundation to discuss patient candidacy as well as surgical and fitting considerations. I will review Ponto practicalities, such as how the processor was designed to be durable and reliable – which is especially important when we fit children. I will talk about the signal processing in the Ponto processors and present evidence that supports how it benefits our youngest bone anchored patients. When fitting children with amplification, what is the goal?

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Clinical Verification of Ear Level FM Systems: Classroom & Personal Use Applications

Dave Smriga: In today’s course, we’ll explore how Audioscan equipment easily facilitates the execution of the most current recommended FM verification procedures. In addition, we’ll discuss how you can use these procedures for both FM system verification and verification of remote microphone technology. Although we will be depicting the various test procedures included in today's webinar with images created using the Verifit2 hearing instrument fitting system, the same tests can be performed with the original Verifit system.

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The Ponto Bone Anchored System: The Right Choice for Pediatrics

Today, I will begin with the fundamentals of bone anchored technology including an overview of osseointegration, and that will give us the foundation to discuss patient candidacy as well as surgical and fitting considerations. I will review Ponto practicalities, such as how the processor was designed to be durable and reliable – which is especially important when we fit children. I will talk about the signal processing in the Ponto processors and present evidence that supports how it benefits our youngest bone anchored patients. When fitting children with amplification, what is the goal?

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Direction-reversing Nystagmus in Horizontal and Posterior Semicircular Canal Canalolithiasis.

Objectives: To investigate the incidence and characteristics of direction-reversing nystagmus in patients with horizontal (HSCC) and posterior semicircular canal (PSCC) canalolithiasis, and evaluate the effect of direction-reversing nystagmus on the treatment outcome. Study Design: A retrospective study. Methods: Between March 2014 and September 2015, 63 and 92 consecutive patients with HSCC and PSCC canalolithiasis, respectively, were enrolled. Positional nystagmus characteristics were examined using video-nystagmography. Results: In HSCC canalolithiasis, direction-reversing nystagmus was observed in 73% of patients (46 of 63), of which 19 cases were bilateral and 27 unilateral. In patients with bilateral reversal, maximal slow-phase velocity (mSPV) was significantly greater when the head turned to the lesioned side than to the healthy side in both the first and second phase. In all patients with unilateral reversal, direction-reversing nystagmus always occurred in the side of stronger initial nystagmus in a supine roll test. The mean mSPV of first phase nystagmus was significantly greater on the side with reversal than without (p

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The Effect of Simulated Mastoid Obliteration on the Mechanical Output of Electromagnetic Transducers.

Background: The electromagnetic transducers of implantable middle ear hearing devices or direct acoustic cochlear implants (DACIs) are intended for implantation in an air-filled middle ear cavity. When implanted in an obliterated radical mastoid cavity, they would be surrounded by fatty tissue of unknown elastic properties, potentially attenuating the mechanical output. Here, the elastic properties of this tissue were determined experimentally and the vibrational output of commonly used electromagnetic transducers in an obliterated radical mastoid cavity was investigated in vitro using a newly developed method. Methods: The Young's moduli of human fatty tissue samples (3-mm diameter), taken fresh from the abdomen or from the radical mastoid cavity during revision surgeries, were determined by indentation tests. Two phantom materials having Young's moduli similar to and higher than (worst case scenario) the tissue were identified. The displacement output of a DACI, a middle ear transducer (MET) and a floating mass transducer (FMT), was measured when embedded in the phantom materials in a model radical cavity and compared with the output of the nonembedded transducers. Results: The here-determined Young's moduli of fresh human abdominal fatty tissue were comparable to the moduli of human breast fat tissue. When embedded in the phantom materials, the displacement output amplitude at 0.1 to 10 kHz of the DACI and MET was attenuated by maximally 5 dB. The attenuation of the output of the FMT was also minor at 0.5 to 10 kHz, but significantly reduced by up to 35 dB at lower frequencies. Conclusion: Using the method developed here, the Young's moduli of small soft tissue samples could be estimated and the effect of obliteration on the mechanical output of electromagnetic transducers was investigated in vitro. Our results demonstrate that the decrease in vibrational output of the DACI and MET in obliterated mastoid cavities is expected to be minor, having no major impact on clinical indication. Although no major attenuation of vibrational output of the FMT was found for frequencies >0.5 kHz, for implantations in patients the attenuation at frequencies

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