Neuroimplant with protective structure

Abstract

Neuroimplant for brain region, featuring: at least one stimulation section (220) to generate electrical stimulation signals for the brain region, an electrode section (600) with at least one electrode, which is coupled to the at least one stimulation section (220) via a direct current connection (700) and can be arranged in the brain area and is designed to apply the electrical stimulation signals to the brain area, and at least a first protective structure section (100) designed to monitor the stimulation section (220), where which at least one first protection structure section (100) is supplied by a first energy supply (110) and which at least one stimulation section (220) is supplied by a second energy supply (210), and the first power supply (110) is galvanically isolated from the second power supply (210).

Description

[0001] The present invention relates to a neuroimplant with a protective structure. Neuroimplants are inserted into the human brain to treat diseases such as Parkinson's disease and epilepsy.

[0002] Neuroimplants comprise sections for the electrical stimulation of neuronal areas of the brain, as well as electrode sections for contacting these brain areas. Neuromodulators, specifically closed-loop neuroimplants, additionally include sections for detecting neuronal activity (i.e., electrical signals) from areas of the brain.

[0003] Strict safety precautions are prescribed for human-implantable neuroimplants, so that even after a so-called first failure, the implant does not pose a danger to the patient's health.

[0004] Early failures include, for example, persistently strong currents flowing from the neuroimplant into the brain due to a malfunction, particularly in the stimulation sections. To prevent such early failures, it is known to insert DC-blocking capacitors between the stimulation and electrode sections. However, these are disadvantageous due to the geometric size of SMD capacitors, which is especially problematic with multichannel neuroimplants. Furthermore, magnetic materials in the capacitor components used cause shadowing of the MRI image near the implant, which can impair or prevent diagnostic results. Special non-magnetic MRI capacitors with the required capacitance are not available.

[0005] Due to the necessary large capacitance of typically about 10µF per capacitor, integration on the chip is therefore impossible.

[0006] It is also known to equip the stimulation sections with fast-acting switches, allowing for a much smaller block capacitance that can be integrated into a chip. However, this comes at the cost of a more complex and circuit-intensive design of the stimulation sections, a large area requirement for the integrated capacitors, and significant limitations on the maximum achievable stimulation current.

[0007] DE 10 2019 214 752 A1 relates to a system for communicating an operating state of a neuronal stimulation device to an individual, comprising a means for determining an operating state of the device, a means for transmitting a first neuronal stimulation signal to a neuronal stimulation device of the individual, which is configured to elicit a sensory percept in the cortex of the individual, wherein the first neuronal stimulation signal indicates the operating state of the device.

[0008] The object of the present invention is therefore to provide a neuroimplant in which the aforementioned technical problems are at least partially alleviated.

[0009] This problem is solved by the neuroimplant according to claim 1. Advantageous further developments are defined in the dependent claims.

[0010] The product provided is a neuroimplant for the brain area, featuring: at least one stimulation section to generate stimulation signals for the brain area, an electrode section with at least one electrode, which is coupled to the at least one stimulation section via a direct current connection and can be arranged in the brain area and is designed to apply the stimulation signals to the brain area, and at least a first protective structure section designed to monitor at least one stimulation section, wherein which at least one first protective structure section is powered by a first energy supply and which at least one stimulation section is powered by a second energy supply, and The first power supply is galvanically isolated from the second power supply.

[0011] The novel first protection structure allows for increased safety in the event of a first failure, without the need for external or internal blocking capacitors between the electrode and stimulation sections. Because at least one first protection structure section is powered by its own independent supply voltage, it remains fully functional even in the event of faults in the neuroimplant chip.

[0012] In a further development of the invention, the at least one stimulation section and at least one detection section, if present, as well as the at least one first protection section, are formed on a common semiconductor substrate. That is, these sections are formed by a system-on-chip (SoC) or ASIC. The purely electrical independence of the at least one first protection section from the at least one stimulation section and the at least one detection section, if present, enables a space-saving design of the neuroimplant on the common semiconductor substrate.

[0013] A self-test, repeatable at any time and using at least one stimulation section, serves as a safeguard against errors in the protective structure.

[0014] The first protection structure section itself consumes no DC operating point current and is very space-efficient.

[0015] The first protection structure section, at least, includes a DC-DC converter that generates reference voltage levels from the supply voltage. A charge pump then generates the corresponding reference voltage levels. These threshold voltages serve to define a voltage window considered safe.

[0016] The first protective structure section, at least, can be further designed to output a signal if at least one of the detected stimulation signals lies outside at least one predetermined voltage range.

[0017] For this purpose, a window threshold detector (window comparator) can be provided, for example comprising two dynamic comparators (e.g., StrongARM latches) with a high-voltage (HV) stable input pair and minor additional digital logic. This can generate a status information flag indicating whether the voltage at the electrode section is within or outside the predetermined voltage window or voltage range, and can thus reliably detect a potential first-fault event.

[0018] The first power supply can be a DC voltage source, and the at least one first protection structure section can include a first DC transformer for generating first reference voltages from the first power supply and a first comparator for comparing the stimulation signals applied to the electrode device with the first reference voltages.

[0019] The DC converter can include a charge pump for generating reference voltages.

[0020] The first protective structure section, at least, may include a window threshold detector to check whether the detected stimulation signals at the electrode section are within a predetermined voltage range.

[0021] The window threshold detector may include a dynamic comparator, in particular a StrongARM Latch.

[0022] In a further embodiment of the invention, the neuroimplant can have at least a second protective structure section comprising a second DC converter for generating second reference voltages from the second power supply and a second comparator for comparing the stimulation signals applied to the electrode device with the second reference voltages.

[0023] The advantages of this implementation are circuit-technically independent realization from the main circuit, i.e. the stimulation section, operation without static DC operating point current (i.e. minimal power consumption), the ability of the system to self-test at any time using the programmable stimulator, the avoidance of external block capacitors and the flexibility through the user-specific programmable voltage limits.

[0024] A galvanic connection between the protection structure section and the stimulation section is only required at the "measuring point," i.e., at the electrode section, to measure the voltage at the electrode device. This allows the protection structure section to monitor the stimulation section and, furthermore, to be simultaneously tested by an external unit using the stimulation section ("self-test"). Periodic self-tests, or monitoring of the status information / flags during each stimulation (approved error messages, as they are self-generated events), increase safety through continuous functionality verification.

[0025] Furthermore, the neuroimplant may be designed to include at least one detection section for detecting signals from the brain region, with this detection section being coupled to the electrode section. In this case, the neuroimplant constitutes a neuromodulator.

[0026] The neuroimplant, in all its embodiments and variants, can be divided into a number of channels, each of which comprises a stimulation section, a detection section, an electrode of the electrode section, and a protective structure section.

[0027] The invention and exemplary embodiments are described in more detail with reference to the drawing. This drawing shows Fig. 1 an embodiment of the invention; Fig. 2 a detail of the protective structure sections according to the embodiment of the invention; and Fig. 3 a voltage-time diagram of a self-test with the protective structure sections according to the embodiment of the invention.

[0028] Fig. Figure 1 illustrates an embodiment of the invention.

[0029] The neuroimplant according to the invention comprises at least one stimulation section 220 for generating stimulation signals for the brain region and an electrode section 600 connected to the stimulation section 220 for contacting the brain region. The electrode section 600, with at least one electrode, is coupled to the stimulation section 220 via a direct current connection 700 for transmitting the stimulation signals. Direct current can flow (in principle, continuously) via the direct current connection 700 between the electrodes of the electrode section 600 and the stimulation section 220. This implies that there can be no capacitors arranged in these connections 700 that could cause direct current decoupling between the electrode and the stimulation section 220.

[0030] Furthermore, the neuroimplant has at least one initial protective structure section 100 for monitoring at least one stimulation section 220 in order to prevent currents permanently flowing into the brain due to a malfunction of the stimulation section 220.

[0031] The first protective structure section 100 is powered by a first power supply 110, while the neuromodulation section 200 is powered by a second power supply 210. The first power supply 110 is galvanically isolated from the second power supply 210. In this context, galvanically isolated means that the two power supplies have no common conductors or a common ground point.

[0032] The first energy supply 110 is therefore independent of the second energy supply 210.

[0033] The connection between the stimulation section 220 and the electrode section 600 has a DC connection 700, meaning it is designed without DC decoupling. Decoupling capacitors are therefore not required in this connection 700.

[0034] The neuroimplant of a variant of the embodiment further comprises at least one detection section 230 for detecting signals from the brain region and is divided into a plurality of identically designed channels 10; a typical number is 32 channels. Fig. Figure 1 merely illustrates channel 10. This neuroimplant is therefore a neuromodulator or closed-loop neuroimplant.

[0035] Electrode section 600 comprises a number of electrodes. The number of electrodes is usually at least as large as the number of channels (10).

[0036] Each channel 10 is assigned or assignable to exactly one electrode of the electrode section 600, one stimulation section 220, one detection section 230 (according to the variant) and one first protective structure section 100.

[0037] Each channel 10 (according to the variant) is bidirectional, meaning it can conduct electrical signals and other electrical quantities in two directions. In one direction, stimulation signals generated by at least one stimulation section 220 are transmitted to the respective electrode; in the opposite direction, neuronal signals from the brain region, detected via the electrode of electrode section 600, are transmitted to at least one detection section 230.

[0038] The stimulation section 220 of each channel 10 includes a digital-to-analog converter (DAC) 221 to generate analog stimulation signals from externally supplied digital control signals. The DAC 221 can be a 5-bit current DAC with a high-voltage push-pull output stage. The high voltage is, for example, 18V.

[0039] The stimulation section 220 can be configured in different modes. In a first mode, it generates current-controlled stimulation (CCS) signals; in a second mode, it generates voltage-controlled stimulation (CVS) signals. In the second mode, the DAC 221 and the high-voltage output are embedded in a DSM-based feedback loop 225.

[0040] In this embodiment, the stimulation section 220 has an increased dynamic range due to scaling of the current mirror gain options. In this embodiment, the dynamic range is 66 dB, with stimulation currents from 5 µA to 10 mA.

[0041] The stimulation section 220 features flexible waveform generation based on a state machine with sequential execution of stimulation commands. This is extended by programmable loops within the command panel, enabling extended repeated execution of waveforms and commands.

[0042] Each first protection structure section 100 includes a voltage monitoring circuit (eVMC). This is connected to the electrode of channel 10. The voltage monitoring circuit is designed as a window comparator.

[0043] In another variant (combinable with any other variant), a second protection structure section 500 is provided for each channel 10. This second protection structure section 500 also represents a voltage monitoring circuit (iVMC). The second protection structure section 500 is electrically independent of the first protection structure section 100. The second protection structure section is powered by the second power supply 210, i.e., by the power supply of the neuromodulator section.

[0044] Thus, two electrically independent instances of voltage monitoring circuits (eVMC, iVMC) or protection structure sections are provided per channel 10.

[0045] The entire neuroimplant can be controlled by a microcontroller unit (MCU, not illustrated).

[0046] Fig. Figure 2 illustrates an example technical design of the first protection structure section 100 and the second protection structure section 500. The window comparators are each implemented using particularly low-noise StrongARM latches. These have high-voltage MOS transistors as input elements, enabling them to withstand the voltages of the stimulation signals at the electrodes. The comparator, which defines the upper limit V lim,p The monitored component is equipped with an NMOS input element, while the comparator, which determines the lower limit V lim,n is monitored and equipped with an HV-PMOS input element.

[0047] The comparators of both protection structure sections 100, 500 are designed for PVT fluctuations of up to 30mV (3σ).

[0048] Apart from that, the two protection structure sections (eVMC, iVMC) 100 and 500 are designed differently. As mentioned above, the first protection structure section (eVMC) 100 is powered by the first power supply 110, which is independent of the second power supply 210 of the second protection structure section (iVMC). The first power supply 110 is the external power supply with respect to the stimulation section 220. It is galvanically isolated from the second power supply 210 and therefore does not share a common conductor path with it.

[0049] The second protective structure section (iVMC) 500 can have digitally programmable voltage ranges or thresholds. These programmable voltage ranges are, for example, ± 375 mV to ± 750 mV or ± 1.125 V to ± 1.5 volts around the body potential point V. CM around. Each of these voltage ranges can be programmed.

[0050] Each of the two protection structure sections 100, 500 triggers a signal, e.g. an interrupt flag, when the voltage value at an electrode leaves the relevant voltage range, so that the MCU can react to it and query which electrode triggered the warning.

[0051] Thus, there are two protective structure sections, 100 and 500, which independently monitor the stimulation sections and the electrodes. This eliminates the need for external isolation capacitors between the electrodes and the neuromodulation section 200.

[0052] The second protection structure section 500 can be designed to output, in addition to the signal or interrupt flag, information about which electrode of the electrode section 600 has a measured voltage outside the predetermined window range.

[0053] The MCU can be further designed to determine whether the cause of the error is a hardware defect, such as a damaged or short-circuited line, or a software defect, such as an incorrectly calculated stimulation signal.

[0054] Depending on the situation, the MCU can then control the stimulation section 220, change the voltage of the stimulation signals (e.g. in case of a software defect), or deactivate the relevant stimulation section 220 (e.g. in case of a hardware defect).

[0055] Furthermore, the second protection structure section 500 can be designed such that the flag, once set, remains set until the error is resolved (by the MCU).

[0056] The first protection structure section 100 can, in principle, be designed in the same way as the second protection structure section 500 with regard to information output. However, if simplicity is paramount, it may be provided that the first protection structure section 100 only outputs the interrupt flag without the information about which electrode of the electrode section 600 the defect occurred at.

[0057] Furthermore, for reasons of simplicity, the first protection structure section 100 can be designed such that the signal or interrupt flag remains set only as long as a faulty voltage is measured by the first protection structure section 100, and disappears immediately when no faulty voltage is measured.

[0058] The monitoring, specifically by the second protective structure section 500, only functions reliably as long as the stimulation section 220 and the detection section 230, implemented on the ASIC, function as intended. If these are faulty and the second monitoring device 500 also fails to function correctly, the first protective structure section 100 remains functional. Although physically combined on the same substrate, it is electrically isolated due to its own primary power supply, which is independent of the voltage supply of the stimulation and detection sections, i.e., galvanically isolated.

[0059] In another embodiment, the neuroimplant has a self-test function for at least one first and / or second protective structure section 100, 500. Here, the respective stimulation section 220 is configured to generate defined voltage patterns and apply them to the respective electrode. This can be controlled by the MCU. The MCU can then check whether the protective structure section 100, 500 outputs a respective interrupt flag and, if applicable, the information about which electrode the voltage occurred at and which voltage threshold was exceeded.

[0060] Fig.Figure 3 shows a diagram of such a self-test for a protection structure section 100, 500. The first and / or the protection structure section 100, 500 is configured here to detect the exceeding of one of four different voltage thresholds and, according to the detected exceeded voltage threshold, to set the information (one of 00, 01, 10, 11 for the detected voltage threshold) to the signal or interrupt flag. The voltage at an electrode V is used for this purpose. EL , in relation to the body potential V CM , starting with the body potential V CM The voltage is continuously changing. The system then checks whether the signal or interrupt flag and the corresponding information (00, 01, 10, 11) are set when the respective voltage threshold is reached. Two bits are sufficient for four different pieces of information (00, 01, 10, 11). The self-test can be controlled by the MCU and can be repeated at any time.

[0061] The neuroimplant further comprises a switch matrix section 240, which is arranged between the electrode section 600 and the at least one detection section 230. The switch matrix section 240 includes switching devices 241, 242 for each channel 10 to couple or decouple the electrode of each channel 10 with the detection section 230 of the channel 10. Additionally, the switch matrix section 240 includes switching devices 243 with which each electrode can be connected to ground (GND). In this way, the respective electrode can, for example, be discharged.

[0062] Furthermore, the switch matrix section 240 includes switching devices 244 with which an electrode (or several electrodes) can be switched as a reference electrode REF. If the electrode is switched as a reference electrode REF, it can be coupled to the reference input, e.g., the inverting input (-) of each detection section 230, while it can be decoupled from the measurement input, e.g., the non-inverting input (+) of the respective detection section 230. In this way, each detection section 230 can receive the potential REF of the reference electrode as the common reference potential.

[0063] This feature is frequently required in practical applications because the characteristics of implanted electrodes are unknown before implantation and can also vary over time, making it disadvantageous to specify a particular electrode as a reference electrode a priori.

[0064] Thus, switch matrix section 240 can be adjusted so that the reference electrode REF is not simultaneously used as a charge sink for the passive discharge of electrodes after stimulation, as this can lead to artifacts and charging of the reference electrode REF. Instead, an electrode different from the reference electrode serves as the ground electrode GND for discharge. This also provides a better reference for detecting and recording the neurosignals.

[0065] Each channel 10 is digitally controlled by a state machine that can be programmed via SPI communication (SPI = Serial Peripheral Interface).

[0066] Furthermore, at least one detection section 230 is designed to be programmable, making it possible to record either local field potentials (LPFs), action potentials (APs) or both bands with selectable gain and bandwidth settings.

[0067] At least one analog-to-digital converter (ADC) is provided to digitize the detected neural signals and generate a data stream via SPI. In one embodiment, two 16-bit ADCs are provided, meaning each ADC can be coupled to 16 channels. Each ADC can be periodically time-division multiplexed to the individual channels to digitize the signals detected via these channels.

Claims

[1] Neuroimplant for brain region, comprising: at least one stimulation section (220) to generate electrical stimulation signals for the brain region, an electrode section (600) with at least one electrode, which is coupled to the at least one stimulation section (220) via a direct current connection (700) and can be arranged in the brain area and is designed to apply the electrical stimulation signals to the brain area, and at least a first protective structure section (100) designed to monitor the stimulation section (220), where which at least one first protection structure section (100) is supplied by a first energy supply (110) and which at least one stimulation section (220) is supplied by a second energy supply (210), and the first power supply (110) is galvanically isolated from the second power supply (210). [2] Neuroimplant (1) according to claim 1, wherein the at least one first protective structure section (100) and the at least one stimulation section (220) are arranged on a common semiconductor substrate and are in particular designed as an ASIC device. [3] Neuroimplant according to one of the preceding claims, wherein the at least one first protective structure section (100) and the at least one stimulation section (220) are galvanically connected to each other only via the electrode section (600) and the at least one first protective structure section is configured to detect the stimulation signals at the electrode section (600). [4] Neuroimplant according to the preceding claim, wherein the at least one first protective structure section (220) is further designed to output a signal (00, 01, 10, 11) when at least one of the detected stimulation signals is outside a predetermined voltage range. [5] Neuroimplant (1) according to one of the preceding claims, wherein the first power supply (110) is a DC voltage source and the first protection structure section (100) comprises a first DC current transformer for generating a first reference voltage from the first power supply (110) and a first comparator for comparing the stimulation signals applied to the electrode device (600) with the first reference voltage. [6] Neuroimplant according to the preceding claim, wherein the DC converter comprises a charge pump for generating reference voltages. [7] Neuroimplant according to the preceding claim, wherein the at least one first protective structure section (100) comprises a window threshold detector for checking whether the detected stimulation signals at the electrode section (600) are outside a predetermined voltage range. [8] Neuroimplant according to the preceding claim, wherein the window threshold detector comprises a dynamic comparator, in particular a StrongARM Latch. [9] Neuroimplant according to one of the preceding claims, further comprising at least a second protective structure section (500) comprising a second DC converter for generating second reference voltages from the second power supply and a second comparator for comparing the stimulation signals applied to the electrode device (600) with the second reference voltages. [10] Neuroimplant according to one of the preceding claims, further comprising at least one detection section (230) for detecting signals from the brain region, wherein the at least one detection section (230) is coupled to the electrode section (600). [11] Neuroimplant (1) according to the preceding claim, wherein the neuroimplant is divided into a number of channels (10), each channel (10) comprising a stimulation section (220), a detection section (230), an electrode of the electrode section (600) and a protective structure section (100). [12] Neuroimplant according to the preceding claim, further comprising a switch matrix section (240) arranged between the electrode section (600) and the at least one detection section (230), wherein the switch matrix section (240) comprises switching devices (241, 242) to couple or decouple the electrode of each channel (10) with the detection section (230) of the channel (10). [13] Neuroimplant according to the preceding claim, wherein the switch matrix section (240) comprises switching devices (244) with which an electrode can each be connected to a ground point (GND). [14] Neuroimplant according to any one of claims 9 to 13, wherein the first and / or the second protection structure section (100, 500) is designed to detect a predetermined voltage threshold from a number of different voltage thresholds and to set a signal (00, 01, 10, 11) when the predetermined voltage threshold is reached. [15] Neuroimplant according to one of the preceding claims, further comprising a self-test mechanism, wherein an electrode voltage (V EL ), relative to a predetermined body potential (V CM ), starting with the body potential (V CM ) is changed and then it is checked whether a signal ( 00, 01, 10, 11) is set when the respective voltage threshold is reached.

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