WO2013101990A1 - Hearing implant fitting with direct mechanical threshold measurement - Google Patents

Abstract

A hearing implant system arrangement and method are described. An implantable signal transducer converts an electrical stimulation signal input into a mechanical stimulation signal output to an auditory structure of the middle ear for perception as sound. An implantable signal processor is coupled to the signal transducer for processing a communication signal input derived from an external sensing microphone to generate the electrical stimulation signal. The signal processor includes a fitting mode of operation with the sensing microphone inoperative, which generates, for each of a plurality of test frequencies, a pure tone test signal to the signal transducer for measurement of a threshold perception level reflecting an individual transfer function of the signal transducer.

Description

TITLE

Hearing Implant Fitting with Direct Mechanical Threshold Measurement

[0001] This application claims priority from U.S. Provisional Patent Application 61/581,168, filed December 29, 2011, which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to a hearing implant, and more specifically to fitting a middle ear implant to an implanted patient.

[0003] A normal ear transmits sounds as shown in Figure 1 through the outer ear 101 to the tympanic membrane (eardrum) 102, which moves the ossicles of the middle ear 103 (malleus, incus, and stapes) that vibrate the cochlea 104. The cochlea 104 is a long narrow organ wound spirally about its axis for approximately two and a half turns. It includes an upper channel known as the scala vestibuli and a lower channel known as the scala tympani, which are connected by the cochlear duct. The cochlea 104 forms an upright spiraling cone with a center called the modiolar where the spiral ganglion cells of the acoustic nerve 113 reside. In response to received sounds transmitted by the middle ear

103, the fluid-filled cochlea 104 functions as a transducer to generate electric pulses which are transmitted to the cochlear nerve 113, and ultimately to the brain.

[0004] Hearing is impaired when there are problems in the ear's ability to transduce external sounds into meaningful action potentials along the neural substrate of the cochlea

104. To improve impaired hearing, various types of hearing prostheses have been developed. For example, when a hearing impairment is related to the operation of the middle ear 103, a conventional hearing aid, a bone conduction implant, or a middle ear implant (MEI) device may be used to provide acoustic-mechanical vibration to the auditory system.

[0005] Fig. 1 also shows some components in a typical MEI arrangement where an external audio processor 111 processes ambient sounds to produce an implant communications signal that is transmitted through the skin to an implanted receiver 108. Receiver 108 includes a receiver coil that transcutaneously receives signals the implant communications signal which is then demodulated into a transducer stimulation signals which is sent over leads 109 through a surgically created channel in the temporal bone to a floating mass transducer (FMT) 110 secured to the incus bone in the middle ear 103. The transducer stimulation signals cause drive coils within the FMT 110 to generate varying magnetic fields which in turn vibrate a magnetic mass suspended within the FMT 110. The vibration of the inertial mass of the magnet within the FMT 110 creates vibration of the housing of the FMT 110 relative to the magnet. This vibration of the FMT 110 is coupled to the incus in the middle ear 103 and then to the cochlea 104 and is perceived by the user as sound. See U.S. Patent 6,190,305, which is incorporated herein by reference.

[0006] After implantation, operation of the MEI system needs to be customized to the specific patient, a process known as fitting. The fitting process chooses between various possible signal processing algorithms and modifies some of the signal processing of any such algorithm. Such fittings may be done manually, automatically, or semi-automatically. Information on patient performance while using the implant system is needed to compare different processing algorithms and/or processing parameters with regards to any differences in the performance of the system or the experience of the patient.

[0007] Existing fitting approaches assume that the values of the standard audiological measurement with acoustic signals reproduced by headphones or speakers are adequate for a first fit algorithm. But the standard audiological measured audiogram does not include variation within the transducer coupling at different frequencies. Quantification of transducer coupling using middle ear implants is only possible using audiological sound field testing which includes in the measurement the amplification provided by the implant.

SUMMARY

[0008] Embodiments of the present invention are directed to an arrangement for fitting a hearing implant system such as a middle ear implant system to an implanted patient. An implantable signal transducer such as a floating mass transducer (FMT) converts an electrical stimulation signal input into a mechanical stimulation signal output to an auditory structure of the middle ear for perception as sound. An implantable signal processor is coupled to the signal transducer for processing a communication signal input derived from an external sensing microphone to generate the electrical stimulation signal. The signal processor includes a fitting mode of operation with the sensing microphone inoperative, which generates, for each of a plurality of test frequencies, a pure tone test signal to the signal transducer for measurement of a threshold perception level reflecting an individual transfer function of the signal transducer.

[0009] The system may further include a fitting module for adjusting the processing of the communication signal based on patient response to the test signals. The threshold perception level may be a lowest perceptible threshold level or a maximum uncomfortable loudness threshold (UCL) level.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 shows various anatomical structures in a human ear containing a middle ear implant device.

[0011] Figure 2 shows he difference between direct mechanical threshold measurement and conventional bone conductions threshold measurements.

[0012] Figure 3 shows one specific embodiment for direct mechanical measurement of thresholds.

[0013] Figure 4 shows an example of a testing interface according to one embodiment of the present invention.

[0014] Figure 5 shows another user interface for calculating fitting adjustments according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0015] Various embodiments of the present invention are directed to techniques for fitting a middle ear implant to an implanted patient by measuring thresholds as determined by directly driving the middle ear transducer at various levels with pure tones that are generated by the implant sound processor. This allows frequency-specific subjective evaluation of hearing threshold levels (THR-softest perceptible sound level) and uncomfortable levels (UCL-loudest tolerable sound level) by directly mechanically driving the inner ear with vibratory energy generated by the middle ear transducer. These levels match the input dynamic range that is important for speech understanding to the dynamic range of the mechanical stimulation from the middle ear transducer to allow a precise individual fitting that optimizes the hearing benefit. This approach is applicable across the entire range of implanted patients independently of hearing loss, surgical technique, and quality of coupling of the transducer to a vibratory structure of the inner ear.

[0016] Existing standard clinical threshold measurements often are not very precise for a given individual patient. As shown in Figure 2, variation of up to 65dB has been observed between the frequency specific threshold measurements by standard audiogram measurement as compared to direct mechanical threshold measurement. Statistical analysis show mode (statistics) in 17.14-32.86% of individual patient frequency-specific thresholds. That means that only about a third to a sixth of overall frequencies are usable when using standard audiological testing. Measuring frequency thresholds directly through the implanted mechanical transducer rather than using headphones or speakers eliminates the issue with these variations.

[0017] Thus, embodiments of the present invention are directed to an arrangement for fitting a hearing implant system such as a middle ear implant system to an implanted patient. In normal operation, an external sensing microphone senses environmental sound that an external processor uses to generate a communications signal that is transmitted through the skin to the implant processor. The implant processor converts the received signal into an electrical stimulation signal for the implanted signal transducer (e.g., a floating mass transducer (FMT)), which converts the electrical stimulation signal input into a corresponding mechanical stimulation signal output to an auditory structure of the middle ear such as the incus or the round window membrane for perception as sound.

[0018] The implanted signal processor also includes a special fitting mode of operation. During the fitting mode, the external sensing microphone is inoperative and the implanted signal processor generates pure test tones at different levels for different test frequencies to test the hearing threshold of the individual patient. For example, 250, 500, 750, 1000, 1500, 2000, 3000, 4000 and 6000 Hz test tones may be generated. These pure tone test signals from the implanted signal processor are delivered to the signal transducer for measurement of a threshold perception level reflecting an individual transfer function of the signal transducer. This direct mechanical measurement allows frequency-specific subjective evaluation of hearing threshold levels (THR-softest perceptible sound level) and uncomfortable levels (UCL-loudest tolerable sound level) by directly mechanically driving the inner ear with vibratory energy generated by the middle ear transducer.

[0019] Figure 3 shows one specific embodiment for direct mechanical measurement of thresholds using an implant system with a fitting process as described above. An audiologist work station 304 includes fitting software (e.g., Symfit software from Vibrant Med-El) and is connected through a fitting interface 303 (e.g., a HiPro box) to an external transmitter coil arrangement 302 on the head of the implanted patient 301. The external transmitter coil arrangement 302 transmits a control signal through the skin to place the implanted signal processor (e.g., Vibrant Soundbridge) in a muted fitting mode in which the normal external communications signal input is muted (disabled). The external software on the audiologist workstation 304 then controls the implanted signal processor to perform the direct mechanical threshold testing by generating the pure test tones at different levels for different test frequencies to test the responses of the individual patient.

[0020] Figure 4 shows an example of a testing interface according to one embodiment of the present invention for direct mechanical threshold measurement. In the example shown in Fig. 4, the vertical columns are test tone frequencies from 250 Hz to 7.5 kHz. For each frequency, the test tone level can be adjusted in 5 dB or 1 dB steps to test hearing thresholds or maximum tolerable levels of the individual patient. The tester varies the loudness of a specific frequency, reducing the level until the patient cannot detect the tone (similar to the measurement of a conventional audiogram). To obtain the most accurate results, it may be useful to repeat the test several times. Maximal tolerable tones can be tested similarly, increasing the level of each direct mechanical test tone until it becomes uncomfortable for the patient. [0021] Figure 5 shows another user interface for calculating fitting adjustments according to an embodiment of the present invention. The interface enables the measured thresholds to be inserted into the fitting software, and an algorithm then calculates frequency-specific gain settings for different fitting strategies (e.g. NAL-NL1, DSL I/O).

[0022] Direct mechanical measurement of hearing thresholds enables a faster fitting procedure with fewer revisits by an implanted patient for fine tuning. By comparing the threshold measurement determined by direct mechanical measurement with the conventional bone conduction threshold measurement, it is possible to gain

qualitative information regarding the coupling between the implant transducer and the target anatomical structure in the middle ear, which other existing threshold measurement approaches cannot provide. The frequency dependent threshold measurement approach also enables a better application calculation for a given fitting strategy (e.g., NAL-NL1 , NAL-NL2, DSL I/O and DSL v5). And there is a frequency by frequency determination of the entire dynamic range heard by the implanted patient.

[0023] Embodiments of the invention maybe implemented in whole or in part in any conventional computer programming language such as VHDL, SystemC, Verilog, ASM, etc. Alternative embodiments of the invention may be implemented as pre-programmed hardware elements, other related components, or as a combination of hardware and software components.

[0024] Embodiments can be implemented in whole or in part as a computer program product for use with a computer system. Such implementation may include a series of computer instructions fixed either on a tangible medium, such as a computer readable medium (e.g., a diskette, CD-ROM, ROM, or fixed disk) or transmittable to a computer system, via a modem or other interface device, such as a communications adapter connected to a network over a medium. The medium may be either a tangible medium (e.g., optical or analog communications lines) or a medium implemented with wireless techniques (e.g., microwave, infrared or other transmission techniques). The series of computer instructions embodies all or part of the functionality previously described herein with respect to the system. Those skilled in the art should appreciate that such computer instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Furthermore, such instructions may be stored in any memory device, such as semiconductor, magnetic, optical or other memory devices, and may be transmitted using any communications technology, such as optical, infrared, microwave, or other transmission technologies. It is expected that such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation ( e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the network ( e.g., the Internet or World Wide Web). Of course, some embodiments of the invention may be implemented as a combination of both software (e.g. , a computer program product) and hardware. Still other embodiments of the invention are implemented as entirely hardware, or entirely software ( e.g. , a computer program product).

[0025] Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the true scope of the invention. For example, although embodiments are described in the specific context of middle ear implant systems, the principles of the invention are equally relevant to other types of hearing implant systems such as bone conduction implant systems.

Claims

CLAIMS What is claimed is :

1. A hearing implant system comprising:

an implantable signal transducer for converting an electrical stimulation signal input into a mechanical stimulation signal output to an auditory structure of the middle ear for perception as sound; and

an implantable signal processor coupled to the signal transducer for processing a communication signal input derived from an external sensing microphone to generate the electrical stimulation signal;

wherein the signal processor includes a fitting mode of operation with the sensing microphone inoperative, generating for each of a plurality of test frequencies a pure tone test signal to the signal transducer for measurement of a threshold perception level reflecting an individual transfer function of the signal transducer.

2. A system according to claim I, further comprising:

a fitting module for adjusting the processing of the communication signal based on subjective patient response to the test signals.

3. A system according to claim 1, wherein the signal transducer is a floating mass transducer (FMT).

4. A system according to claim 1, wherein the system is a middle ear implant system.

5. A system according to claim 1, wherein the system is a bone conduction implant system.

6. A system according to claim 1, wherein the threshold perception level is a lowest perceptible threshold level.

7. A system according to claim 1, wherein the threshold perception level is a maximum uncomfortable loudness threshold (UCL) level.

8. A method for fitting a hearing implant system to an implanted patient, the method comprising:

for a hearing implant system having:

i. an implantable signal transducer for converting an electrical stimulation signal input into a mechanical stimulation signal output to an auditory structure of the middle ear for perception as sound, and

ii. an implantable signal processor coupled to the signal transducer for processing a communication signal input derived from an external sensing microphone to generate the electrical stimulation signal,

disabling the sensing microphone;

generating for each of a plurality of test frequencies a pure tone test signal to the signal transducer; and

measuring a threshold perception level reflecting an individual transfer function of the signal transducer.

9. A method according to claim 8, further comprising:

adjusting the processing of the communication signal based on subjective patient response to the test signals.

10. A method according to claim 8, wherein the signal transducer is a floating mass transducer (FMT).

11. A method according to claim 8, wherein the system is a middle ear implant system.

12. A method according to claim 8, wherein the system is a bone conduction implant system.

13. A method according to claim 8, wherein the threshold perception level is a lowest perceptible threshold level.

14. A method according to claim 8, wherein the threshold perception level is a maximum uncomfortable loudness threshold (UCL) level.