System And Method For Diagnosis Of Brainstem Disorders

Abstract

A system and method for detection of a brainstem disorder, such as schizophrenia, by means of brainstem audiometry is disclosed. A subject's (4) responses on the physical properties of sound; frequency, time and amplitude are being detected. Sound stimuli are being presented, via a communication element (2) through a hearing organ (3) to the subject. Elements (7) are attached to the subject (7) for measurement of the subject's electrophysiological brain activity. Simultaneously as the mentioned sound stimuli (1) are presented to the subject (4) a trig signal is sent out from the organ for generation of stimuli (1), via a trig box (5), further to an organ for registration (6) of the electro-physiological brain activity in the subject (4), whereafter mentioned electrophysiological brain activity is stored and imaged, in computer equipment (8) for determination of a brainstem disorder in the subject.

Claims

1. A method of detecting brainstem disorders in a subject comprising: generating a sound stimuli; communicating said sound stimuli to the subject; recording an electrophysiological brain activity response from said subject substantially simultaneously to the communication of said sound stimuli to said subject; comparing said electrophysiological brain activity response to standardized responses from a reference population; and, determining whether the subject has a brainstem disorder based upon said comparison.

2. The method according to claim 1, further comprising imaging said electrophysiological brain activity response.

3. The method according to claim 1, wherein the recording of the electrophysiological brain activity response comprises measuring an auditory brainstem response.

4. The method according to claim 3, wherein said measuring of an auditory brainstem response comprises measuring brainstem activity within a time span of approximately 0 to 10 ms after the generating of said sound stimuli.

5. The method according to claim 1, wherein the generating a sound stimuli comprises generating a sequence of sound stimuli tests.

6. The method according to claim 5, wherein said sequence of sound stimuli tests comprises: a forward masking test; a backward masking test; a binaural forward masking test; a directional hearing test; a perception of distance in sounds test; a pulse train 1 test; a pulse train 2 test; a pulse train 3 test; and a pulse train 4 test.

7. The method according to claim 5, wherein each sound stimuli test comprises the repetition of said sound stimuli approximately 500-1500 times and where a time between each repetition is approximately 150 to 500 ms.

8. The method according to claim 1, wherein said sound stimuli having defined physical properties in frequency, time and amplitude.

9. The method according to claim 1, further comprising triggering said recording of the electrophysiological brain activity simultaneously as said sound stimuli is communicated to the subject.

10. The method according to claim 9, further comprising imaging said electrophysiological brain activity response when said triggering is made.

11. The method according to claim 1, further comprising conducting a test battery for detecting said brainstem disorder, wherein said test battery comprises nine tests, wherein each test consists of presentation of said sound stimuli to the subject and registration of the electrophysiological responses to mentioned sound stimuli, wherein said sound stimuli are presented in repeated sequences.

12. The method according to claim 1, further comprising reproducing and storing said electrophysiological activity on a computer equipment.

13. The method according to claim 8, further comprising detecting said brainstem disorders by means of auditory brain stem audiometry, wherein the subject's response to the physical properties of sound, namely frequency, time and amplitude is detected by conducting a test comprising at least three subtests

14. The method according to claim 1, wherein said brainstem disorder is schizophrenia.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and other aspects, features and advantages of which the invention is capable of will be apparent and elucidated from the following description of exemplary embodiments of the present invention, reference being made to the accompanying drawings in which

[0017] FIG. 1 is a schematic illustration of a system according to one embodiment of the present invention,

[0018] FIG. 2 is a timing diagram that presents common features, as for instance for nine tests in one embodiment of the present invention, and

[0019] FIGS. 3, 4 and 5 are schematic illustrations and diagrams that further illustrate the nine test's sound stimuli according to one embodiment of the present invention.

[0020] Abbreviations used in FIGS. 1 to 5: [0021] A=The amplitude of the sound stimuli [0022] U=The voltage of the trigger pulse [0023] Tt=Time between the trig pulses [0024] Ts=The duration of sound stimuli [0025] G=Number of repetitions of the stimuli for a test [0026] Sssp=square-shaped sound pulse (fp) [0027] B fbw=Butterworth filtered white noise [0028] T isi=Time between square-shaped sound pulses for test 16 [0029] A fp=The amplitude variation for the square-shaped sound pulses for test 17 [0030] f=The frequency for the reference square-shaped sound pulse for test 18 [0031] f fp=The frequency variation for the square-shaped sound pulse for test 18 [0032] t fpd=The duration variation for the square-shaped sound pulse for test 19

DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention comprises a system and a method intended for diagnosis and/or therapeutic control of brains stem disorders, such as schizophrenia. In this aspect the system and method thereof, comprise means of auditory brainstem audiometry.

[0034] The present invention is not intended to be limited to diagnosis and/or control of schizophrenia, even though schizophrenia is mentioned in the embodiments of the present invention. Rather, the present invention includes the diagnosis and/or therapeutic control of all disorders assignable to brainstem related disorders.

[0035] By using the physical properties of sound; frequency, time and amplitude, and the knowledge that these three properties, or combinations of these, is treated in different networks in the brain, a number of specific subtests have been created, which have been proven to separate schizophrenic subjects from psychiatrically healthy reference subjects. More specifically this is achieved by letting the subject undergo a test, comprised of a number of subtests. During the test procedure electrophysiological signals from the brain stem are registered, which reflect the different sound stimuli and furthermore the results are stored, analyzed and interpreted. The final result is a profile of the brainstems audio-physiological functioning.

[0036] Both the composition of the sound stimuli and the method of analyzing the schizophrenia-specific electrophysiological response pattern, are new methodological concepts which makes identification of the early stages in brains stem related diseases, such as schizophrenia, possible, which in turn facilitates efficient treatment with adequate therapeutic resources in time.

[0037] The present invention at hand does not rely on any cognitive effort from the subject during the testing procedure. The test is automated, and does not need the active contribution of the test object. Furthermore, the technique has never before been used for psychiatric diagnostic purposes.

[0038] Audiometry has been used for examination and as a diagnostic instrument of organic conditions in the central nervous system, e.g. measurement of hearing thresholds in infants and for subjects who not are able to be tested with routine audiogram. However, it has not been use for diagnosing of brainstem related diseases. Brainstem audiometry is characterized by an electrophysiological imaging method of the brainstems coding during stimulation with different sound sequences.

[0039] In one embodiment, according to FIG. 1, the system according to the present invention comprises an apparatus for generation of stimuli (1), such as a tone generator according to the present embodiment, by means of which the aforementioned sound stimuli are being presented, via a communication element (2), such as a plastic hose, cord or an electric cable, and a sound generating device (3), such as a hearing phone, to a subject (4). A plastic hose has the advantage that it does not generate electromagnetic fields near the test subject, which may interfere with brainstem activity or the measurements thereof.

[0040] Simultaneously as the sound stimuli are being presented, a trig-pulse is being emitted from the system for generation of stimuli (1) to a triggering device (5), such as a trig-box, and further on to an apparatus for analysis and storage of information (6), such as brainstem activity, in which registration of electrophysiological brain activity from electrodes (7) is initiated, whereafter the activity is imaged on an equipment (8), such as a computer equipment. The triggering of registration is hence initiated by each start of a stimuli.

[0041] This system may, in one embodiment of the present invention, be used to perform a test-battery for schizophrenia consisting of nine tests, in which each test comprises presentation of stimuli to a subject and registration of the response elicited by mentioned sound stimuli. Common features for the nine tests are that the sound stimuli being presented to the subject are presented in repeated sequences; typically sound stimuli are repeated approximately 500-1500 times and the time between stimuli varies from approximately 150 to 500 ms. Hence, a complete test with high reliability is provided that takes some minutes, compared to weeks according to the prior art. Because of the fact that each stimulation is registered when the trig-pulse initiates the imaging apparatus, the brain activity caused by the stimulation appears more significantly on a continuous basis in relation to other brainstem activity. In this way the brainstems specific responses to stimuli are registered. The recorded electrophysiological responses from the subject are thereafter compared with standardized responses from a reference population.

[0042] The present invention differs among other things from the prior art in that the apparatus for generation of stimuli (1) is configured to transmit, or send, a triggering signal, via and/or through the triggering device (5), to the apparatus for analysis and storage of information (6) of the electrophysiological brain activity simultaneously as said sound stimuli is transmitted to the subject (4) from the apparatus for stimuli generation (1).

[0043] Therefore, the present invention uses according to some embodiments auditory brainstem response (ABR) to detect brain disorders, such as schizophrenia.

[0044] The term “auditory brainstem response” is commonly used to define electrophysiological measurement of the activity of the brainstem within a time span of 0 to approximately 10 ms. Of course this time span may vary somewhat, but not principally deviate from this time span, while still be inside the scope of the present invention, according to the appended claims.

[0045] The present invention comprises triggering of brainstem reading in relation to complex sound sequences, which are specifically developed for diagnostic and detecting purposes regarding brain disorders, such as schizophrenia. Hereby, the present invention comprises triggering in respect of sound experiencing mechanisms and not general neurological phenomena, such as detection of difference. Thus, the triggering according to the present invention is inseparable from the complex sound stimuli, presented herein.

[0046] Some of the tests in the present invention are based on auditory masking. Masking is defined as the subjects reduced ability to hear one sound in the presence of another sound presented simultaneously, before or after the sound one are trying to hear. These processes are handled by general coding principles within the nervous system. Information is sorted and rudimentary parts of it are damped or filtered away. This is made out by feedback-mechanisms in the nervous system which facilitates or inhibits impulses. Said sorting is handled by priority or down-regulation between different mechanisms, working more or less independently of each other.

[0047] Furthermore, directional hearing is investigated, which refers to the ability of spatial location of sounds. Both left/right-ability and coding of distance are investigated. Left/right-ability is most crucially determined by the time-difference between the sounds arrival to the left and right ears. Perception of distance is based on neural analysis of spectral cues, which thus comprises more complex handling.

[0048] One group of tests examines how the neural coding of auditory input is influenced by time, amplitude and frequency. These tests aim at the different underlying structures in the brain that handle the specific aspects of stimuli. Time analysis for example demands involvement from the brains feedback system in the frontal lobes; analysis of amplitude and modulation comprises mechanisms in different loci in the brainstem and coding of frequency is based on at least three different systems for detection. It is to be understood that modifications and alterations of said tests are possible while still being inside the scope of the present invention. Therefore, these tests are to be interpreted as examples of possible tests, and not to limit the scope of protection of the present invention in any way.

[0049] Thus, in one embodiment of the present invention one group of tests or one example of a test battery are/is provided according to the tests 1 to 9 below.

Test 1 “Forward Masking”

[0050] “Forward masking” (11) means the reduced ability to perceive one sound in the presence of another temporally preceding sound. In this test the stimuli consist of a Butterworth-filtered white noise (b fbw) which masks a subsequent square-shaped sound pulse (sssp).

Test 2 “Backward Masking”

[0051] “Backward masking” (12) means the reduced ability to perceive one sound in the presence of another temporally following sound. In this test the stimuli consist of a Butterworth-filtered white noise (b fbw) which masks a preceding square-shaped sound pulse (sssp).

Test 3 “Binaural Forward Masking”

[0052] “Binaural forward masking” (13) is characterized by the reduced ability to perceive a sound in one ear in the presence of another temporally preceding sound presented in the other ear. In this test the stimuli consist of a Butterworth-filtered white noise (b fbw) in one ear which masks a subsequent square-shaped sound pulse (sssp) in the other ear.

Test 4 “Directional Hearing”

[0053] In the test “Directional hearing” (14) square-shaped sound pulses (sssp) are presented in separate steps from left to right in equidistant angle-steps. This test consists of five subtests, each with its own specific angle (a-e). In the first subtest the sound originates completely from left (e). In subtest number two the pulse train are presented from an angle of 45° left (d). Subtest number three consists of a pulse train from the front (c). In the fourth subtest the pulse train are presented from 45° right (b) and finally subtest number five 90° right (a).

Test 5 “Perception of Distance in Sounds”

[0054] The test “Perception of distance in sounds” (15) consist of a number of subtests. In the first of these a pulse train consisting of square-shaped sound pulses (sssp) is used as stimulus (g). This subtest creates a reference value. In the second subtest (h) the square-shaped sound pulses have been altered through artificial treatment which makes them being perceived as originating from a distant location. In the following subtests the square-pulses in the pulse trains are even more modulated and thus are perceived as being more distantly located.

Test 6 “Pulse Train 1”

[0055] The test “Pulse train 1” (16) is comprised by a number of subtests. The subtests consists of pulse trains with specific time intervals (t isi) between the included square-shaped pulses (fp). In the first subtest the time interval has a constant value. In the other subtests the mentioned time interval is modified.

Test 7 “Pulse Train 2”

[0056] The test “Pulse train 2” (17) is comprised by a number of subtests. In the first subtest the included square-shaped pulses have specified constant amplitudes. For the other subtests this value is modified (a fp), and each subtests square-shaped pulses (fp) have their own specific constant amplitude.

Test 8 “Pulse Train 3”

[0057] The test “Pulse train 3” (18) is comprised by a number of subtests. In the first subtest the included square-shaped pulses have specified constant frequencies. For the other subtests this value is modified (f fp), and each subtests square-shaped pulses (fp) have their own specific constant frequency. The frequencies of the square-shaped pulses are obtained through filtering with a Butterworth-filter.

Test 9 “Pulse Train 4”

[0058] The test “Pulse train A” (19) is comprised by a number of subtests. In the first subtest the included square-shaped pulses have a specified constant duration. For the other subtests this value is modified (t fpd), and each subtests square-shaped pulses (fp) have their own specific constant duration.

[0059] The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit, or may be physically and functionally distributed between different units.

[0060] Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and, other embodiments than the specific above are equally possible within the scope of these appended claims.

[0061] In the claims and description above, the term “comprises/comprising” does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. The terms “a”, “an”, “first”, “second” etc do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

[0062] Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.