Intracranial pressure measurement device, intracranial pressure measurement method, program for intracranial pressure measurement

Abstract

To acquire information on an intracranial pressure in a non-invasive manner.SOLUTION: An intracranial pressure measurement device 1 includes: a stimulation sound output unit 91 configured to output stimulation sound toward the inside of an external acoustic meatus of a subject; a sound reception unit 92 configured to acquire a sound pressure signal indicating pressure variation inside the external acoustic meatus when the stimulation sound is output; and an analysis device 93 configured to derive a value related to an intracranial pressure of the subject by analyzing the sound pressure signal.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an intracranial pressure measurement device, an intracranial pressure measurement method, and a program for intracranial pressure measurement, and particularly relates to trans-tympanic and non-invasive intracranial pressure measurement.

Background Art

[0002] Bleeding in the brain and poor circulation of cerebrospinal fluid cause an increase (elevation) in intracranial pressure. After neurosurgery and the like, measurement of intracranial pressure is performed for the management of the patient's condition. As a general method for measuring intracranial pressure, a method is known in which a catheter is directly inserted into the skull or lumbar vertebra, and a pressure gauge is attached to the other end of the catheter to measure intracranial pressure or cerebrospinal fluid pressure. However, these measurement methods are invasive. There is a need for a method of non-invasively measuring intracranial pressure.

[0003] For example, Patent Document 1 discloses the following about a method of non-invasively estimating intracranial pressure. The blood flow pulse wave ejected from the heart reaches the brain via the carotid artery and vertebral artery, thereby forming an intracranial pressure pulse wave. The transfer function from this carotid artery wave to the intracranial pressure pulse wave shows resonance characteristics. When intracranial pressure increases, brain compliance decreases, and the natural resonance frequency in the above resonance characteristics increases. There is a quadratic function relationship between intracranial pressure and the natural resonance frequency. Therefore, an earplug-type pressure sensor is used to acquire an intracranial pressure pulse wave signal in the external auditory canal, the signal is analyzed to obtain the above natural resonance frequency, and intracranial pressure is calculated from this natural resonance frequency. In this way, intracranial pressure can be estimated non-invasively.

[0004] Although some proposals have been made for means of non-invasively acquiring information regarding intracranial pressure, none of them have been generally used at present.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The present invention aims to acquire information on intracranial pressure in a non-invasive manner. [Means for solving the problem]

[0007] According to one aspect of the present invention, the intracranial pressure measuring device comprises a stimulus sound output unit configured to output a stimulus sound towards the external auditory canal of a subject, a sound receiving unit configured to acquire a sound pressure signal indicating pressure fluctuations in the external auditory canal when the stimulus sound is output, and an analysis device configured to analyze the sound pressure signal and derive a value relating to the intracranial pressure of the subject. [Effects of the Invention]

[0008] According to the present invention, information regarding intracranial pressure can be obtained non-invasively. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing an example of the configuration of an intracranial pressure measuring device according to one embodiment. [Figure 2] Figure 2 is a functional block diagram illustrating a schematic configuration example of an intracranial pressure measuring device according to one embodiment. [Figure 3] Figure 3 is a schematic diagram showing the human auditory organ and its surrounding area. [Figure 4A] Figure 4A is a diagram illustrating the sound pressure within the external auditory canal. [Figure 4B] Figure 4B is a diagram illustrating the sound pressure within the external auditory canal. [Figure 5] Figure 5 is a diagram illustrating the measurement using an intracranial pressure measurement device. [Figure 6] Figure 6 is a schematic flowchart illustrating an example of the operation of the computer in an intracranial pressure measuring device according to one embodiment. [Figure 7] FIG. 7 is a flowchart showing an outline of an example of the operation of a computer of an intracranial pressure measuring device according to an embodiment. [Figure 8] FIG. 8 is a diagram showing an example of measurement results using an intracranial pressure measuring device with an adult as a subject. [Figure 9A] FIG. 9A shows the values of resonance frequencies obtained in a normal state and an excited state. [Figure 9B] FIG. 9B shows the values of ΔSPL obtained in a normal state and an excited state. [Figure 10A] FIG. 10A shows the values of resonance frequencies obtained in a normal state and an excited state normalized by the values in the normal state. [Figure 10B] FIG. 10B shows the values of ΔSPL obtained in a normal state and an excited state normalized by the values in the normal state.

MODE FOR CARRYING OUT THE INVENTION

[0010] An embodiment will be described with reference to the drawings. This embodiment relates to an intracranial pressure measuring device that acquires information related to intracranial pressure (ICP). The intracranial pressure measuring device of this embodiment is configured to measure intracranial pressure trans-tympanically, particularly trans-tympanically. The intracranial pressure measuring device outputs a stimulus sound toward the ear canal of the subject and acquires the pressure fluctuation in the ear canal at that time. The intracranial pressure measuring device is configured to analyze this pressure fluctuation to analyze the characteristics of the middle ear of the subject and derive a value related to the intracranial pressure that affects the characteristics of the middle ear.

[0011] [Device Configuration] FIG. 1 is a schematic diagram showing an outline of a configuration example of an intracranial pressure measuring device 1 according to this embodiment. FIG. 2 is a functional block diagram showing an outline of a configuration example of the intracranial pressure measuring device 1 according to this embodiment. As shown in FIG. 1, the intracranial pressure measuring device 1 includes a computer 10, an AD / DA converter 60, an amplifier system 70, and a probe 80.

[0012] The probe 80 is configured such that its tip is inserted into the external auditory canal 210 of the subject 200. The probe 80 includes an earphone 82 for outputting a stimulus sound toward the external auditory canal 210 and a microphone 84 for acquiring pressure fluctuations within the external auditory canal 210.

[0013] The computer 10 is a general computer, such as a personal computer or the like. The computer 10 includes various integrated circuits such as, for example, a Central Processing Unit (CPU) 11, a memory 12, etc., a storage 13, various interfaces 14, etc. The computer 10 performs processes such as controlling the operation of the intracranial pressure measuring device 1, generating signals related to the stimulus sound, and analyzing the pressure fluctuations within the external auditory canal. The operation of the computer 10 is performed according to a program recorded within the computer 10 or provided from outside the computer 10.

[0014] The AD / DA converter 60 has a DA converter 62 and an AD converter 64. The amplifier system 70 has an earphone amplifier 72 and a microphone amplifier 74. The DA converter 62 of the AD / DA converter 60 converts the digital signal related to the stimulus sound output from the computer 10 into an analog signal and outputs it to the earphone amplifier 72 of the amplifier system 70. The earphone amplifier 72 amplifies the analog signal related to the stimulus sound input from the DA converter 62 and causes the earphone 82 of the probe 80 to output the stimulus sound. The microphone amplifier 74 of the amplifier system 70 amplifies the analog signal related to the pressure fluctuations within the external auditory canal 210 acquired by the microphone 84 of the probe 80 and outputs it to the AD converter 64 of the AD / DA converter 60. The AD converter 64 converts the analog signal acquired from the microphone amplifier 74 into a digital signal and inputs it to the computer 10.

[0015] The computer 10 has functions as a control unit 22, a signal generation unit 32, a signal output unit 34, a signal acquisition unit 38, a signal analysis unit 40, etc. The control unit 22 controls each operation of the computer 10.

[0016] The signal generation unit 32 generates a signal related to the stimulus sound to be output. The generated signal related to the stimulus sound is output to the DA converter 62 via the signal output unit 34.

[0017] In this embodiment, the system is configured to output sounds of multiple frequencies as the stimulus sound. For example, the stimulus sound may be a frequency-swept sound that changes from low frequency to high frequency, or from high frequency to low frequency. For example, the stimulus sound may be a frequency-swept sound that changes from 100 Hz to 2000 Hz over 10 seconds. Furthermore, the stimulus sound may not have a continuously changing frequency like a frequency-swept sound, but rather a discontinuously changing frequency. Also, the stimulus sound may include sounds of each frequency range from low to high, such as random noise.

[0018] The signal analysis unit 40 acquires signals related to pressure fluctuations in the external auditory canal from the AD converter 64 via the signal acquisition unit 38 and the microphone 84. The signal analysis unit 40 analyzes the acquired signals. The signal analysis unit 40 also functions as a middle ear characteristic analysis unit 42 and an intracranial pressure analysis unit 44.

[0019] The middle ear characteristic analysis unit 42 analyzes the characteristics of the subject's middle ear based on the acquired pressure fluctuations within the external auditory canal 210. Based on the acquired pressure fluctuations within the external auditory canal 210, the middle ear characteristic analysis unit 42 calculates, for example, the resonant frequency of the subject's eardrum 222 or a value indicating the mobility of the eardrum 222. If the stimulus sound is random noise, the analysis performed by the middle ear characteristic analysis unit 42 may include Fast Fourier Transform (FFT) analysis.

[0020] The intracranial pressure analysis unit 44 is configured to derive values ​​related to the intracranial pressure of the subject 200 based on the characteristics of the middle ear determined by the middle ear characteristic analysis unit 42. For example, the intracranial pressure analysis unit 44 is configured to derive values ​​related to the intracranial pressure of the subject 200 based on the resonant frequency of the tympanic membrane 222 or a value indicating the mobility of the tympanic membrane 222. The intracranial pressure analysis unit 44 is configured to derive values ​​related to intracranial pressure, such as the absolute value of intracranial pressure, the relative value of intracranial pressure to a reference value, or the change in intracranial pressure over time.

[0021] As described above, the signal generation unit 32, signal output unit 34, DA converter 62, earphone amplifier 72, earphone 82, etc., together function as a stimulus sound output unit 91 configured to output stimulus sounds into the external auditory canal 210 of the subject 200. The signal acquisition unit 38, AD converter 64, microphone amplifier 74, microphone 84, etc., together function as a sound receiving unit 92 configured to acquire a sound pressure signal indicating the pressure fluctuation in the external auditory canal 210 when the stimulus sound output unit 91 outputs a stimulus sound. The signal analysis unit 40, including the middle ear characteristic analysis unit 42 and the intracranial pressure analysis unit 44, etc., functions as an analysis device 93 configured to analyze the sound pressure signal and derive values ​​related to the intracranial pressure of the subject 200.

[0022] The configuration of the intracranial pressure measurement device 1 shown here is just one example, and can be modified as needed to perform similar functions. Here, we have shown an example in which the computer 10 performs all of the various controls and data analysis related to the operation of the intracranial pressure measurement device 1, but this is not limited to this. The functions of the computer 10 may be realized by any number of devices. In addition, some of the functions of the computer 10 may be performed by other devices located in remote locations that are connected to the computer 10 via a network. For example, the operation of each part of the intracranial pressure measurement device 1 may be controlled remotely, or the analysis of acquired data may be performed on a server. Various physical configurations are possible, but the intracranial pressure measurement device 1 performs functions such as a stimulus sound output unit 91, a sound receiving unit 92, and an analysis device 93.

[0023] [Measurement principle] The principle of measuring intracranial pressure using the intracranial pressure measuring device 1 will be explained. Figure 3 is a schematic diagram showing the human auditory organ and its surroundings. The eardrum 222 at the end of the external auditory canal 210 and the cochlea 232 of the inner ear 230 are connected via ossicles 224, including the malleus 225, incus 226, and stapes 227. The inner ear 230 is filled with lymph fluid. The cochlea 232 of the inner ear 230 and the subarachnoid space 242 are connected by cochlear canaliculi 234. Therefore, when the pressure in the subarachnoid space 242, i.e., intracranial pressure, increases, the pressure of the lymph fluid in the inner ear 230 also increases, and the stapes 227 connected to the inner ear 230 is pushed towards the middle ear 220. As the stapes bone 227 is displaced, the tympanic membrane 222 is pushed towards the external auditory canal 210 via the incus bone 226 and malleus bone 225 connected to it. At this time, the mobility of the tympanic membrane 222 is reduced compared to normal. Thus, since there is a relationship between the mobility characteristics of the tympanic membrane 222 and intracranial pressure, information regarding intracranial pressure can be obtained by measuring the mobility characteristics of the tympanic membrane 222.

[0024] The sound pressure inside the external auditory canal 210 will now be explained. During measurement, the diaphragm 83 of the earphone 82 vibrates at one end of the external auditory canal 210, and the eardrum 222 vibrates at the other end of the external auditory canal 210. Figures 4A and 4B schematically illustrate this process.

[0025] When the frequency of the stimulus sound output from the earphone 82 is lower than the resonant frequency of the middle ear 220, the diaphragm 83 of the earphone 82 and the eardrum 222 are displaced in phase, as schematically shown in Figure 4A. Therefore, the pressure P inside the external auditory canal 210 is P=K(ΔV-ΔV TM ) / V It is expressed as follows: Here, K is the bulk modulus of air, ΔV is the volume change due to the diaphragm 83 of the earphone 82, ΔV TM V is the volume change due to the eardrum 222, and V is the volume of the external auditory canal 210. In this case, the more the eardrum 222 vibrates, the smaller the volume change becomes, and the lower the sound pressure becomes.

[0026] When the frequency of the stimulus sound output from the earphone 82 reaches the resonant frequency of the middle ear 220, the phase of the eardrum 222 inverts, as schematically shown in Figure 4B. Therefore, the pressure P inside the external auditory canal 210 is P=K(ΔV+ΔV TM ) / V This is represented by [formula]. In this case, the greater the vibration of the eardrum 222, the greater the volume change and the greater the sound pressure.

[0027] Figure 5 shows an example of measurement results using the intracranial pressure measurement device 1 with adult subjects 200. Figure 5 shows the results acquired using the microphone 84 when a frequency sweep sound, whose frequency changes from 100 Hz to 2000 Hz over 10 seconds, is output from the earphone 82. In Figure 5, the solid line shows the sound pressure level (SPL) acquired using the microphone 84 against the frequency of the stimulus sound. Here, SPL is, SPL = 20 log | P / P REF | And P is the sound pressure measured by microphone 84, and P REF This is the reference sound pressure, which is 2.0 × 10⁻⁶ -5 This is Pa. The curve shown by the solid line in Figure 5 will be called the SPL curve. In Figure 5, the dashed line shows the volume change due to the eardrum 222 as a function of the stimulus sound frequency.

[0028] Large changes in SPL observed in the SPL curve are known to indicate resonance in the middle ear 220. In Figure 5, the midpoint between the frequency showing the minimum and maximum values ​​of the SPL curve is shown as the resonance frequency (RF) of the middle ear 220, indicated by a dashed-dotted arrow. Furthermore, ΔSPL, which is the difference between the minimum and maximum values ​​of the SPL curve, is known to indicate the mobility of the tympanic membrane 222. As described above, since there is a relationship between intracranial pressure and the mobility characteristics of the tympanic membrane 222, information related to intracranial pressure can be obtained by identifying the resonance frequency (RF) and / or ΔSPL of the middle ear 220.

[0029] [Device Operation] The operation of the intracranial pressure measurement device 1 will now be described. In this example, the intracranial pressure measurement device 1 repeatedly identifies values ​​related to intracranial pressure, for example, periodically, and analyzes its changes over time. During measurement, the probe 80 is inserted into the external auditory canal 210 of the subject 200. Figure 6 is a schematic flowchart of an example of the operation of the computer 10.

[0030] In step S11, the computer 10 determines whether or not it is time to measure the value related to intracranial pressure. If it is not time to measure, the computer 10 waits for the right time to measure. If it is time to measure, the process proceeds to step S12.

[0031] In step S12, the computer 10 performs intracranial pressure measurement processing. An example of intracranial pressure measurement processing will be explained with reference to the flowchart shown in Figure 7.

[0032] In step S21, the computer 10 sets the frequency of the stimulus sound to be output. For example, the frequency of the stimulus sound is set to sweep from low frequency to high frequency.

[0033] In step S22, the computer 10 outputs a signal relating to a stimulus sound of a set frequency. Based on this signal, the stimulus sound is output from the earphone 82 to the ear canal 210 via the DA converter 62 and the earphone amplifier 72.

[0034] At this time, a signal indicating the sound pressure inside the external auditory canal 210 is generated by the microphone 84. The signal generated by the microphone 84 is input to the computer 10 via the microphone amplifier 74 and the AD converter 64. In step S23, the computer 10 acquires the sound pressure signal from the microphone 84.

[0035] In step S24, the computer 10 determines whether measurements have been taken for all frequencies for which sound pressure should be acquired. If measurements have not been taken for all frequencies, the process returns to step S21. That is, the frequency of the stimulus sound is changed and sound pressure is acquired in the same way. In step S24, if it is determined that measurements have been taken for all frequencies, the process proceeds to step S25. In this way, the sound pressure inside the ear canal 210 for stimulus sounds of each frequency is acquired.

[0036] In step S25, the computer 10 analyzes the characteristics of the subject 200's middle ear 220 based on the acquired sound pressure information. For example, the computer 10 identifies the resonant frequency of the middle ear 220 and / or the ΔSPL value indicating the mobility of the eardrum 222 based on the SPL curve.

[0037] In step S26, the computer 10 derives a value related to intracranial pressure based on the identified characteristics of the middle ear 220. The value related to intracranial pressure may be, for example, an absolute value representing intracranial pressure or a relative value representing intracranial pressure. This completes the intracranial pressure measurement process.

[0038] Returning to Figure 6, the explanation continues. After the intracranial pressure measurement process, the process proceeds to step S13. In step S13, the computer 10 analyzes the changes in intracranial pressure over time based on the intracranial pressure values ​​acquired over time. For example, the computer 10 identifies whether or not there is an increase in intracranial pressure. The process then returns to step S11, and the above process is repeated.

[0039] According to the intracranial pressure measuring device 1 operating as described above, values ​​related to intracranial pressure can be obtained non-invasively via the extraaural auditory canal, and a judgment can be made, including whether or not there is an increase in intracranial pressure.

[0040] [Measurement example] Using a measuring device with the configuration of intracranial pressure measuring device 1, the stimulus sound was a frequency sweep sound that changed from 100 Hz to 2000 Hz over 10 seconds, and the sound pressure level (SPL) inside the external auditory canal was measured. The measured SPL was plotted against the frequency of the stimulus sound to obtain an SPL curve.

[0041] It is known that straining after inhalation increases intrathoracic pressure, compressing the lungs and heart, and reducing venous return due to venous compression, thus increasing intracranial blood volume and temporarily raising intracranial pressure. It is thought that straining at an expiratory pressure of 30 mmHg increases intracranial pressure by about 10 mmHg. Therefore, we measured intracranial pressure in a state of increased intracranial pressure while straining after inhalation. We also measured pressure in a normal state without straining.

[0042] In preliminary experiments, male subjects were able to stably maintain an expiratory pressure of 40 mmHg for 10 seconds while straining. Therefore, for male subjects, the expiratory pressure was set to 40 mmHg, the straining state was defined as an increased intracranial pressure state, and measurements were taken to obtain the SPL curve. On the other hand, in preliminary experiments, many female subjects were unable to stably maintain an expiratory pressure of 40 mmHg for 10 seconds while straining. Female subjects were able to stably maintain an expiratory pressure of 30 mmHg for 10 seconds while straining. Therefore, for female subjects, only when they were able to stably maintain an expiratory pressure of 40 mmHg while straining was the expiratory pressure set to 40 mmHg and the straining state was defined as an increased intracranial pressure state. In all other cases, the expiratory pressure was set to 30 mmHg and the straining state was defined as an increased intracranial pressure state, and measurements were taken to obtain the SPL curve.

[0043] For each subject, measurements were taken in a normal state, and then in a strained state, and SPL curves were obtained for both states.

[0044] Measurements were taken in 10 adults (5 males, 5 females, 22.8 ± 2.5 years old) who were confirmed to have good hearing. Measurements were taken for both ears. The results for 12 ears from which the subject was able to maintain expiratory pressure while straining and for which an SPL curve was obtained were analyzed.

[0045] An example of the measurement results is shown in Figure 8. In Figure 8, the solid line shows the SPL curve obtained under normal conditions, and the dashed line shows the SPL curve obtained under strained conditions, i.e., under conditions of increased intracranial pressure. Compared to the normal conditions shown by the solid line, the ΔSPL was smaller and the resonant frequency (RF) was higher under the conditions of increased intracranial pressure shown by the dashed line.

[0046] The resonant frequency and ΔSPL values ​​were determined from the SPL curves obtained from 12 ears during measurement. The obtained resonant frequency and ΔSPL values ​​for the 12 ears are shown in Figures 9A and 9B, respectively. In these figures, the values ​​for the normal state are shown on the left axis, the values ​​for the strained state are shown on the right axis, and the results for the same ear are shown by lines. Furthermore, the resonant frequency and ΔSPL values ​​normalized to the values ​​for the normal state are similarly shown in Figures 10A and 10B, respectively. In all measured ears, the resonant frequency was higher in the strained state than in the normal state. In addition, when the obtained resonant frequencies were tested for significance, the resonant frequency was significantly higher in the strained state compared to the normal state. Also, in many of the measured ears (10 ears), ΔSPL was smaller in the strained state than in the normal state.

[0047] The increase in resonant frequency and decrease in ΔSPL during straining suggest that, in a strained state, i.e., when intracranial pressure increases, the pressure of the lymphatic fluid in the inner ear increases, pushing the stapes towards the middle ear and reducing the mobility of the stapes.

[0048] These results confirm that it is possible to monitor changes in intracranial pressure by obtaining SPL curves and analyzing the resonant frequency and / or ΔSPL.

[0049] Furthermore, based on the relationship between the resonant frequency and / or ΔSPL and intracranial pressure, it was confirmed that the value of intracranial pressure can be derived from the measured resonant frequency and / or ΔSPL.

[0050] Individual differences can exist in the characteristics of the middle ear. Therefore, in this embodiment, information regarding the characteristics of the middle ear at each frequency is obtained by inputting multiple frequencies, such as acquiring an SPL curve. In this way, information regarding intracranial pressure can be accurately obtained transmiddle ear, regardless of individual differences in middle ear characteristics.

[0051] Furthermore, although the above-described embodiment shows an example in which the pressure inside the external auditory canal is measured as atmospheric pressure, it is not limited to this. Similar measurements may be performed using a pressure other than atmospheric pressure, or similar measurements may be performed while varying the pressure inside the external auditory canal relative to atmospheric pressure, for example, from +200 daPa to -200 daPa. In addition, measurements may be performed while changing various other conditions.

[0052] The intracranial pressure measuring device 1 according to this embodiment can be used not only for measuring intracranial pressure after neurosurgery, but also for patients whose intracranial pressure needs to be monitored over several months to several years, such as pediatric hydrocephalus patients. Generally, in pediatric hydrocephalus patients, the presence or absence of elevated intracranial pressure is qualitatively monitored by measuring head circumference or directly palpating the anterior fontanelle. Using the intracranial pressure measuring device 1 according to this embodiment, intracranial pressure can be monitored simply, non-invasively, and quantitatively in addition to these methods.

[0053] Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention.

[0054] For example, in the above embodiment, the resonant frequency or ΔSPL is determined based on the SPL curve, and information regarding intracranial pressure is obtained based on this, but this is not limited to this. Information regarding intracranial pressure may be obtained based on other values ​​that indicate the characteristics of the middle ear obtained from the SPL curve, rather than the resonant frequency or ΔSPL. Also, the characteristics of the middle ear may be obtained without using an SPL curve. The stimulus sound preferably relates to multiple frequencies, but it may relate to only one frequency. Since the pressure fluctuations in the external auditory canal when a stimulus sound is input indicate the characteristics of the middle ear, values ​​indicating the characteristics of the middle ear may be derived from the pressure fluctuations in the external auditory canal obtained when a stimulus sound is input, based on various analyses. Information regarding intracranial pressure can be obtained from these values ​​indicating the characteristics of the middle ear. [Explanation of symbols]

[0055] 1. Intracranial pressure measurement device 10 Computers 11 CPU 12 memory 13 Storage 14 Interfaces 22 Control Unit 32 Signal generation unit 34 Signal output section 38 Signal acquisition unit 40 Signal analysis section 42 Middle ear characteristics analysis section 44 Intracranial Pressure Analysis Unit 60 AD / DA Converters 62 DA converter 64 AD converters 70 Amplifier System 72 Earphone Amplifier 74 Microphone Amplifier 80 probes 82 earphones 83. Vibrating membrane 84 Microphones 91 Stimulus sound output section 92 Sound receiver 93 Analyzer 200 subjects 210 External auditory canal 220 middle ear 222 Tympanic membrane 224 ear ossicles 230 Inner Ear 232 Snails 234 Snail tubes 242 submembranous space

Claims

1. A sound output unit configured to output a sound stimulus towards the external auditory canal of the subject, A sound receiving unit configured to acquire a sound pressure signal indicating pressure fluctuations within the external auditory canal when the aforementioned stimulus sound is output, An analysis device configured to analyze the sound pressure signal and derive a value relating to the intracranial pressure of the subject, Equipped with, The stimulus sound output unit is configured to output stimulus sounds of multiple frequencies. Intracranial pressure measuring device.

2. The intracranial pressure measuring device according to claim 1, wherein the analysis device is configured to analyze the characteristics of the middle ear of the subject and derive a value relating to the intracranial pressure based on the characteristics of the middle ear.

3. The intracranial pressure measuring device according to claim 1, wherein the analysis device is configured to calculate a value indicating the resonant frequency of the middle ear or the mobility of the eardrum of the subject, and to derive a value relating to the intracranial pressure based on said value.

4. The intracranial pressure measuring device according to claim 1, wherein the stimulus sound output unit is configured to output a frequency sweep sound or random noise as the stimulus sound.

5. The intracranial pressure measuring device according to any one of claims 1 to 4, wherein the analysis device is configured to derive the change in intracranial pressure over time as a value relating to the intracranial pressure.

6. The process involves outputting a stimulating sound into the subject's external auditory canal, To acquire a sound pressure signal indicating the pressure fluctuations within the external auditory canal when the aforementioned stimulus sound is output, The sound pressure signal is analyzed to derive a value relating to the intracranial pressure of the subject. Includes, Outputting the aforementioned stimulus sound includes outputting the aforementioned stimulus sound relating to multiple frequencies. Methods for measuring intracranial pressure.

7. The stimulus sound output unit outputs a stimulus sound towards the subject's external auditory canal, The sound receiving unit is configured to acquire a sound pressure signal indicating the pressure fluctuations within the external auditory canal when the stimulus sound is output. The analysis device analyzes the sound pressure signal to derive a value related to the intracranial pressure of the subject. Make it run, The stimulus sound output unit is configured to output stimulus sounds of multiple frequencies. A program for measuring intracranial pressure.

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