Tinnitus testing device using brain waves and tinnitus testing method using same

Abstract

The tinnitus testing apparatus of this invention comprises a control part that in turn comprises: an auditory stimulus generation part that can generate a stimulus; and an AEP acquisition and amplitude measurement part that can acquire auditory evoked potential (AEP) brain waves of a examinee due to said stimulus and measure the specific amplitude of said acquired brainwaves; wherein said auditory stimulus is one or more of: a 1st stimulus containing continuous noise and pulse noise; and a 2nd stimulus containing pulse noise and continuous noise with a silent gap.

Claims

1. A tinnitus testing apparatus that tests for tinnitus in a patient, the tinnitus testing apparatus comprising: a control system comprising at least one processor, the at least one processor which executes one or more processor-executable instructions that cause the at least one processor to: generate an auditory stimulus having an adjustable frequency, said auditory stimulus including a 1st auditory stimulus containing continuous noise and pulse noise and a 2nd auditory stimulus containing pulse noise and continuous noise with a silent gap; receive signals that represent auditory evoked potential (AEP) brainwaves of the patient due to said auditory stimuli; measure an N1-P2 amplitude of said received signals representative of the AEP brainwaves; selectively vary the adjustable frequency of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus output during a first time period; determine a frequency for said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus based at least in part upon a maximum N1-P2 amplitude from the signals representative of the AEP brainwaves during the first time period; during a second time period adjust the adjustable frequency of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus that is output by the tinnitus testing apparatus based at least in part upon the determined frequency; determine a G/N ratio of the N1-P2 amplitude of an N1-P2 response evoked by said 2nd stimulus to the N1-P2 amplitude of an N1-P2 response evoked by said 1st stimulus; and at least one earphone, the at least one earphone which is communicatively coupled to the control system, the at least one earphone which generates audible sound based upon at least one of the 1st auditory stimulus and the 2nd auditory stimulus during the first time period and which generates audible sound based upon at least one of the 1st auditory stimulus and the 2nd auditory stimulus during the second time period.

2. The tinnitus testing apparatus of claim 1, wherein the at least one processor executes one or more processor-executable instructions that cause the at least one processor to change the adjustable frequency of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus within an arbitrary range during the first time period in which the arbitrary range includes a tinnitus frequency as confirmed via a tinnitogram frequency match.

3. The tinnitus testing apparatus of claim 2, wherein the at least one processor executes one or more processor-executable instructions that cause the at least one processor to: modify an adjustable loudness of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus within an arbitrary range during the first time period in which the arbitrary range includes a tinnitus loudness as confirmed via a tinnitogram loudness match, determine a loudness of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus based at least in part upon the maximum N1-P2 amplitude measured during the first time period, and during the second time period, set the adjustable loudness of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus based at least in part upon the determined loudness.

4. A tinnitus testing apparatus that tests for tinnitus in a patient, the tinnitus testing apparatus comprising: a control system comprising at least one processor, the at least one processor which executes one or more processor-executable instructions that cause the at least one processor to: for each of a plurality of intervals, generate an auditory stimulus having an adjustable frequency, said auditory stimulus including a 1st auditory stimulus containing continuous noise and pulse noise and a 2nd auditory stimulus containing pulse noise and continuous noise with a silent gap; receive signals that represent auditory evoked potential (AEP) brainwaves of the patient due to said auditory stimuli; measure an N1-P2 amplitude of said received signals representative of the AEP brainwaves; selectively vary the adjustable frequency of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus output during a first time period; determine a frequency for said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus based at least in part upon a maximum N1-P2 amplitude from the signals representative of the AEP brainwaves during the first time period; and during a second time period adjust the adjustable frequency of said continuous noise in the 1st auditory stimulus and of said continuous noise in the 2nd auditory stimulus that is output by the tinnitus testing apparatus based at least in part upon the determined frequency; and at least one earphone, the at least one earphone which is communicatively coupled to the control system, the at least one earphone which generates audible sound based upon at least one of the 1st auditory stimulus and the 2nd auditory stimulus during the first time period and which generates audible sound based upon at least one of the 1st auditory stimulus and the 2nd auditory stimulus during the second time period, wherein the at least one processor executes one or more processor-executable instructions that cause the at least one processor to, for each 2nd auditory stimulus in each of the plurality of intervals, alter the duration of the continuous noise between said silent gap and pulse noise within an arbitrary range based on a specific time, and wherein, based on the measured N1-P2 amplitude value measured for each respective interval of the plurality of intervals: if there is a proportional change in N1-P2 amplitude with respect to the duration of the continuous noise, the patient is judged to have tinnitus; if there is a change in N1-P2 amplitude but no proportional trend is confirmed, the a reliability of the test is judged to be poor; and if there is no change in N1-P2 amplitude, the patient is confirmed to be free of tinnitus.

5. The tinnitus testing apparatus of claim 4, wherein the at least one processor executes one or more processor-executable instructions that cause the at least one processor to determine a G/N ratio of the amplitude of N1-P2 response evoked by said 2nd stimulus to the amplitude of N1-P2 response evoked by said 1st stimulus.

6. The tinnitus testing apparatus of claim 5, wherein said tinnitus testing apparatus further comprises: a sound pressure level measuring device, one side whereof is communicatively coupled to the control system, the sound pressure level measuring device which calibrates said generation of the auditory stimulus; and an amplifier that is communicatively coupled to said control system and to the at least one earphone.

7. The tinnitus testing apparatus of claim 1, wherein said tinnitus testing apparatus further comprises: a sound pressure level measuring device, one side whereof is communicatively coupled to the control system, the sound pressure level measuring device which calibrates said generation of the auditory stimulus; and an amplifier that is communicatively coupled to said control system and to the at least one earphone.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1(a) is a graph measuring the startle reflex in animals for auditory stimulus with no silent gap; FIG. 1(b) is a graph measuring the startle reflex in animals for auditory stimulus with a silent gap.

(2) FIG. 2 is a graph showing in detail the N1 evoke d response and P2 evoked response measured by the tinnitus testing apparatus according to one embodiment of this invention.

(3) FIG. 3(a) is a graph showing the N1-P2 reaction measured when applying a continuous noise and pulse noise to a tinnitus-free normal human in the absence of a silent gap; FIG. 3(b) is a graph showing the N1-P2 reaction measured when applying a continuous noise and pulse noise to a tinnitus-free normal human with a silent gap.

(4) FIG. 4 is a schematic view of the tinnitus testing apparatus according to one embodiment of this invention.

(5) FIG. 5 is a graph showing the average values of the N1-P2 amplitude with respect to the 1st stimulus and the N1-P2 amplitude with respect to the 2nd stimulus using the tinnitus analysis apparatus according to one embodiment of this invention on a group of tinnitus-free normal persons.

(6) FIG. 6 is a graph showing the average values of the N1-P2 amplitude with respect to the 1st stimulus and the N1-P2 amplitude with respect to the 2nd stimulus using the tinnitus analysis apparatus according to one embodiment of this invention on a group of tinnitus patients.

(7) FIG. 7 is a graph showing the respective average values upon calculating the GIN ratios for the normal group and the patient group.

(8) FIG. 8 is a diagram of the method of setting the optimized frequency for the continuous noise for each patient by means of the optimal stimulus selecting part of the tinnitus testing apparatus according to one embodiment of this invention.

(9) FIG. 9 is a diagram of the method of setting the optimized loudness of the continuous noise for each patient by means of the optimal stimulus selecting part of the tinnitus testing apparatus according to one embodiment of this invention.

(10) FIG. 10 is a diagram of the method of performing secondary verification of the presence or absence of tinnitus by means of the secondary tinnitus verification part of the tinnitus testing apparatus according to one embodiment of this invention.

MODE FOR INVENTION

(11) Hereinbelow, a preferred embodiment of the apparatus for testing tinnitus using brain waves, and of the method of tinnitus testing using same, will be described with reference to the attached drawings. In the process, the thickness of lines or size of components in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are defined with reference to the functionality of this invention; this may differ depending on the intentions or habits of the user or operator. Therefore, the definitions of these terms must be determined on the basis of the overall content of this specification.

(12) In this specification, a method and apparatus are described for more objectively measuring the presence or absence of tinnitus by measuring the N1 and P2 reactions and the amplitude between N1-P2, but it is significant that, inasmuch as diverse types of brain waves not specifically mentioned in this specification, such as wave I, II, III, IV, V, P300, etc., exhibit similar appearances to the n1 and P2 reactions, a method and apparatus is feasible that uses this fact to more objectively measure the presence or absence of tinnitus.

EMBODIMENTS

(13) FIG. 2 is a graph showing in detail the N1 evoke d response and P2 evoked response measured by the tinnitus testing apparatus according to one embodiment of this invention.

(14) When an auditory stimulus such as sound is applied to the human body, brainwave reactions occur including the Auditory Brain-stem Response (ABR), Middle Latency Response (MLR) and Late Latency Response (LLP).

(15) Here the Middle Latency Response denotes a reaction occurring between approximately 15 and 50 msec after an auditory stimulus, and Late Latency Response denotes a reaction occurring from approximately 75 to 200 msec, and more specifically from about 80 to 100 msec, after the auditory stimulus; these reactions occur in the central auditory pathway.

(16) The N1 and P2 reactions correspond to the Late Latency Response; as described below in this specification, by measuring the N1 and P2 reactions and the N1-P2 amplitude, the presence or absence of tinnitus can be measured more objectively.

(17) Reviewing in detail, in humans, measurement of the startle reflex as is done with the animal testing methods of the prior art is difficult and also inappropriate, since habitualization can easily occur. Accordingly, in the method and apparatus for tinnitus testing according to one embodiment of this invention, the auditory evoked response is used in place of the startle reflex as the primary outcome measure. The auditory evoked response is considered to originate in the central auditory pathway, which includes the primary auditory cortex. Thus, this has a similar character to the startle reflex measured in animals, since if a small auditory stimulus is applied, the N1-P2 reaction amplitude is reduced, and if a large auditory stimulus is applied, the N1-P2 reaction amplitude is increased. However, N1-P2 is more accurate and has greater reproducibility than the startle reflex, and also differs in that there is no reduction in reaction due to habitualization.

(18) FIG. 3(a) is a graph showing the N1-P2 reaction measured when applying a continuous noise and pulse noise to a tinnitus-free normal human in the absence of a silent gap; FIG. 3(b) is a graph showing the N1-P2 reaction measured when applying a continuous noise and pulse noise to a tinnitus-free normal human with a silent gap.

(19) Referring to FIG. 3, the N1 reaction can be measured about 100 msec after the auditory stimulus has occurred. In this case, for normal persons without tinnitus, if there is no silent gap, then just as in the case of the startle reflex, a high N1-P2 amplitude is measured; however, if there is a silent gap, a lower N1-P2 amplitude is measured. Because tinnitus-free patients can perceive the silent gap, the brain wave reaction to the pulse sound that occurs subsequently is reduced. In contrast, in the case of a patient with tinnitus, because the silent gap is filled by the tinnitus, the patient does not perceive there to be a silent gap, and therefore the brain wave reaction to the pulse sound that occurs subsequently is identical.

(20) Therefore, the tinnitus testing apparatus and method according to one embodiment of this invention can objectively distinguish between patients with and without tinnitus by using the above-described principles.

(21) The tinnitus testing apparatus according to one embodiment of this invention will now be described with reference to FIG. 4.

(22) The control part (100) comprises an auditory stimulus generation part (110), AEP acquisition and amplitude measurement part (120), and GIN ratio calculation part (130).

(23) The control part (100) processes data and any storage-capable medium is sufficient; the stimulus generation part (110), AEP acquisition and amplitude measurement part (120) and G/N ratio calculation part (130) are simply functional divisions for the purpose of explaining this invention, and it should be borne in mind that there is no requirement to divide these functions or divide the information processing apparatus. In addition, with regard to the “generation” of the auditory stimulus, it must be understood that the stimulus need not solely be produced by the control part (100) but that the concept of importing the auditory stimulus via an external memory medium is also included.

(24) The stimulus generation part (110) generates the auditory stimulus, and this stimulus may comprise a 1st stimulus that includes a continuous noise and pulse noise, and a 2nd stimulus that includes a pulse noise and continuous noise with a silent gap.

(25) The 1st stimulus and/or 2nd stimulus generated by the stimulus generation part (110) may be played to the examinee (1) via an amplifier (300) and headphone (or earphone), etc. Calibration can then be performed by connecting the stimulus generation part with a sound level meter (200) such as a probe microphone that measures the sound pressure next to the ear drum within the outer ear, so as to transmit a stimulus of an intensity appropriate to the examinee.

(26) The stimulus for generating the N1 and P2 reactions in humans can be described in greater detail as follows. As described hereinabove, the 1st stimulus comprises a continuous noise and pulse noise; the 2nd stimulus comprises a continuous noise with silent gap and a pulse noise.

(27) The N1 and P2 reactions of the examinee (1) to the auditory stimulus are measured by the AEP acquisition and amplitude measurement part (120). Therefore, unlike the methods and apparatus of the prior art, an objective response can be measured even if the examinee (1) exhibits no particular physical reaction. The AEP acquisition and amplitude measurement part (120) can measure the N1-P2 amplitude as well as the N1 and P2 reactions.

(28) The G/N ratio calculation part (130) acts to calculate the G/N ratio of the N1-P2 amplitude for said 2nd stimulus to the N1-P2 amplitude for said 1st stimulus.

(29) In other words, the G/N ratio represents either the quotient of the N1-P2 amplitude for the 2nd stimulus, which includes a silent gap, divided by the N1-P2 amplitude for the 1st stimulus, which does not include a silent gap, or 100 times this value.

(30) Significantly, in the ideal case, the G/N ratio for normal persons without tinnitus will be lower than the standard value, and the G/N ratio for patients with tinnitus will be higher than the standard value (approaching 1 or 100%).

(31) The control part (100) links the output part (130) and input part (140). The output part (130) can depict the stimulus used in the experiment, the N1-P2 amplitudes measured for said stimuli, and said G/N ratio, as a graph or as certain numeric data. A command can be selected via the input part (140) whereby the stimulus is selected or the stimulus is played to the examinee (1), or the experimental results are analyzed. In addition, the results of a subjective tinnitus determination method of the prior art can be entered via the input part (140) and output together with the results according to the apparatus according to one embodiment of this invention and compared.

(32) In order to measure the presence or absence of tinnitus in a examinee using the tinnitus testing apparatus according to one embodiment of this invention, the type of auditory stimulus, such as 1st stimulus or 2nd stimulus, is first selected by means of the input part (140). Here it is significant that with regard to the stimulus, the loudness and frequency of the continuous noise, the intervals between pulse noise and silent gap, and the loudness and duration of the pulse noise, can also be adjusted.

(33) Next, if the stimulus selected by manipulation of the control part (100) is played to the examinee (1), the consequent N1-P2 reaction and amplitude, etc., of the examinee (1) are measured by means of the AEP acquisition and amplitude measurement part (120). Here it is significant that the N1-P2 amplitude for the 1st stimulus and the N1-P2 amplitude for the 2nd stimulus can be stored either temporarily or permanently in the control part (100).

(34) Next, based on the measured N1-P2 amplitudes, the GIN ratio calculation part (130) calculates the GIN ratio of the N1-P2 amplitude for said 2nd stimulus to the N1-P2 amplitude for said 1st stimulus.

(35) Next, the control part (100) determines whether the examinee suffers from tinnitus by comparing the calculated GIN ratio to the standard value. Here, it is preferable that said standard value be a clinically significant standard value set based on experiments and statistics, and may e.g. be between 0.7 and 0.9. If said calculated ratio is greater than said standard value, the examinee is judged to have tinnitus.

(36) The results measured by this method can be reviewed as follows.

(37) FIG. 5 is a graph showing the average values of the N1-P2 amplitude with respect to the 1st stimulus and the N1-P2 amplitude with respect to the 2nd stimulus using the tinnitus analysis apparatus according to one embodiment of this invention on a group of tinnitus-free normal persons (7 male, 1 female, average age: 29.4±3.0).

(38) FIG. 6 is a graph showing the average values of the N1-P2 amplitude with respect to the 1st stimulus and the N1-P2 amplitude with respect to the 2nd stimulus using the tinnitus analysis apparatus according to one embodiment of this invention on a group of patients with tinnitus (3 male, 1 female, average age: 38.0±23.1).

(39) FIG. 7 is a graph showing the respective average values upon calculating the GIN ratios for the normal group and the patient group.

(40) Referring to FIGS. 5 through 7, it is evident that the GIN ratio in the normal group was measured as comparatively low, at 79.2±14.7 (average approximately 78%), and the G/N ratio in the patient group was measured as comparatively high, at 5.6±19.9 (average approximately 97%). Specifically, it is preferable that the standard value for determining the presence or absence of tinnitus be a clinically significant value (e.g. 70% to 90%); if the G/N ratio of examinees whose tinnitus status is unknown is greater than said standard value, the examinee is judged to have tinnitus, thereby enabling the presence or absence of tinnitus to be determined more objectively.

(41) Using the above-described apparatus and testing method, the presence or absence of tinnitus can be verified objectively. However, in order to increase the reliability of the test results and minimize the likelihood of error, a process of optimization is undertaken for each individual. Because the loudness and frequency of the tinnitus as subjectively felt by the patient can differ from what is actually perceived in the patient's brain, a process of optimizing the test for the conditions perceived in the brain is needed in order to further maximize the difference in results between normal examinees and tinnitus patients. This is because, in the absence of optimization, even if tinnitus is actually perceived in the brain, there is a possibility that the tinnitus will not be confirmed by the brainwave result.

(42) To this end, the tinnitus testing apparatus according to one embodiment of this invention can additionally be furnished with an optimal stimulus selecting part (160).

(43) The optimal stimulus selecting part (160) is intended for optimization of the stimulus, and specifically the frequency and loudness of the continuous stimulus, and thus is an element that can optimize the tinnitus frequency and tinnitus loudness, which differ for each patient.

(44) Reviewing the functionality of the optimal stimulus selecting part (160), the optimal stimulus selecting part (160) enables the stimulus generation part (110) to transform the frequency of the generated continuous noise to the tinnitus frequency, ±1 KHz, or ±2 KHz, based on the tinnitus frequency for each patient as confirmed via tinnitogram frequency match. The pulse noise is kept at a frequency of about 1 KHz. Then for each case, the frequency of the continuous noise is selected as the frequency with the greatest amplitude when compared to the N1-P2 amplitude measured via the AEP acquisition and amplitude measurement part (120) (the frequency with the greatest amplitude being the one closest to the tinnitus frequency of the tinnitus patient).

(45) For example, referring to FIG. 8, when a stimulus has been applied having a continuous noise of 8 kHz, 9 kHz, or 10 kHz with a silent gap and a pulse noise (approx. 1 kHz tone), the N1-P2 amplitude is judged to be greatest when the frequency of the continuous noise is 8 kHz, and therefore in this case it is evident that 8 kHz is most appropriate as the frequency of the continuous noise.

(46) Thereafter, the optimal stimulus selection part (160) enables the stimulus generation part (110) to transform the generated loudness of the continuous noise to ±1 dB SL, ±2 dB SL, in 1 dB SL units, based on the selected frequency of the continuous noise and the loudness confirmed by means of a tinnitogram loudness match. The pulse noise is kept at a frequency of about 1 KHz. Then for each case, the loudness of the continuous noise is selected as the loudness with the greatest amplitude when compared to the N1-P2 amplitude measured via the AEP acquisition and amplitude measurement part (120) (the loudness with the greatest amplitude being the one closest to the tinnitus loudness of the tinnitus patient).

(47) For example, referring to FIG. 9, when a stimulus has been applied having a continuous noise of 8 kHz with a silent gap and a pulse noise (approx. 1 kHz tone), the N1-P2 amplitude is judged to be greatest when the loudness of the continuous noise has reached an appropriate level, and therefore in this case it is evident that said appropriate level is most appropriate as the loudness of the continuous noise.

(48) By means of this process, the continuous noise frequency and loudness optimized by the optimal stimulus selecting part (160) are applied to the 1st stimulus and 2nd stimulus, and as described hereinabove, by measuring the N1-P2 amplitude, it is made possible to more precisely measure the presence or absence of patients with the tinnitus testing apparatus according to one embodiment of this invention. The process up to this point is defined as the 1st tinnitus verification process.

(49) In the use of the tinnitus testing apparatus as described, even if the tinnitus detection result is incorrect due to an accidental brain wave abnormality, there is no method for verifying whether there has been an error in the measurement process. However, this problem can be addressed by going through a secondary verification process added to the primary verification.

(50) To this end, the tinnitus testing apparatus according to one embodiment of this invention can additionally be furnished with a secondary tinnitus verification part (not shown).

(51) The secondary tinnitus verification part is intended for the more accurate verification of the presence or absence of tinnitus, and is an element that can further improve the reliability of the test results.

(52) Reviewing the functionality of this secondary tinnitus verification part, the secondary tinnitus verification part enables the stimulus generation part (110) to transform the generated silent gap and pulse noise interval by ±20 msec, ±40 msec, based on a specific time (e.g. 50 msec). Then for each case, the N1-P2 amplitude measured by means of the AEP acquisition and amplitude measurement part (120) is compared.

(53) By means of this result, if the N1-P2 amplitude value is changed, the patient is determined to be normal, and if the measured N1-P2 amplitude value is constant, a final determination is made that the patient has tinnitus.

(54) For example, referring to FIG. 10, if the silent gap and inter-pulse intervals are 50 msec, 30 msec, 10 msec, then in the case of a patient with tinnitus, a constant N1-P2 value will be measured, while in the case of a normal tinnitus-free patient, the N1-P2 amplitudes will gradually undergo a proportionate decrease.

(55) In normal persons, the difference in brain waves trends gradually and proportionally upward as the interval position is optimized, based on the dose response relationship; therefore, by this principle, even if there have been some accidental abnormal brain waves once or twice in the testing, the likelihood that the overall proportional trend itself will break down is reduced. In addition, because a case which the overall proportional trend does break down would indicate low reliability of the test, it could be readily recognized as an error in the measurement process. Thus, by means of this process, the errors in testing can be positively reduced and the reliability of the test can be enhanced.

(56) Hereinabove, this invention has been depicted and described in relation to a specific embodiment; however, this invention is not limited thereto, and it will be readily evident to a person of ordinary skill in the art that this invention can be altered and converted in various ways without departing from the scope of this invention as laid out in the claims below.

INDUSTRIAL APPLICABILITY

(57) The apparatus of this invention for testing tinnitus using brainwaves, and the tinnitus testing method using same, can be applied and used effectively in all fields of industry related to medical devices, due to the advantage it affords of being able to more objectively evaluate the presence or absence of tinnitus.