Evoked Neural Response Detection Under Signal Window Truncation
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Solution Overview
Problem
Existing neuromodulation systems face challenges in accurately measuring evoked neural responses due to the overlap of stimulus crosstalk and artefact with the neural response, particularly in compact implantable devices where the neural response is truncated, making it difficult to maintain stimulus intensity within a therapeutic range.
Innovation Solution
A model-based detector is used to estimate the amount of truncation of the neural response and adjust parameters such as the delay of a correlation-based detector to mitigate truncation, allowing for accurate measurement and control of neural stimulus intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact implantable device is used, then device size is reduced, but the neural response becomes truncated due to overlap with stimulus crosstalk and artefact
Solution Approach 1:
The system performs preliminary actions by delivering a test stimulus before the therapeutic stimulus and measuring the evoked neural response. This preliminary measurement allows the system to characterize the neural response template and timing, which is then used to configure the detection parameters for the subsequent therapeutic stimulation, ensuring accurate measurement despite the compact device constraints
Solution Approach 2:
The system implements feedback by continuously monitoring the evoked neural response during therapeutic stimulation and using this information to adjust stimulation parameters. The measured neural response amplitude and timing are fed back to the control unit, which modifies the therapeutic stimulus to maintain optimal therapeutic effect while avoiding discomfort, thereby resolving the measurement accuracy issue in compact devices
2Reliability
If stimulus intensity is increased to maintain therapeutic effect, then neural recruitment is improved, but uncomfortable or painful percepts arise due to over-recruitment of Aβ fibres
Solution Approach 1:
The system uses feedback control by measuring the evoked neural response amplitude and using it to adjust the stimulus intensity. The control unit compares the measured response to a target range and modifies the therapeutic stimulus parameters to maintain the neural response within the therapeutic window, preventing both under-recruitment (ineffective therapy) and over-recruitment (patient discomfort)
Solution Approach 2:
The system changes stimulation parameters dynamically based on measured neural response characteristics. By adjusting pulse width, amplitude, or frequency of the therapeutic stimulus according to the evoked response, the system maintains reliable therapeutic effect while avoiding the discomfort threshold, effectively managing the trade-off between therapeutic reliability and patient comfort
3Adaptability or versatility
If electrode array position changes due to migration or postural changes, then neural recruitment efficacy is altered, but maintaining appropriate stimulus intensity becomes difficult
Solution Approach 1:
The system implements adaptive feedback control that continuously monitors the evoked neural response and automatically adjusts stimulation parameters to compensate for electrode migration or postural changes. When position changes alter the neural recruitment, the feedback loop detects the changed response characteristics and modifies the stimulus intensity or configuration to restore optimal therapeutic effect, making the system adaptable without requiring manual reconfiguration
Solution Approach 2:
The system transitions from static to dynamic operation by continuously adapting stimulation parameters based on real-time neural response measurements. The control unit dynamically adjusts therapeutic stimulus parameters in response to changing electrode-neuron geometry caused by migration or posture changes, maintaining ease of operation through automated adaptation rather than requiring manual intervention
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables precise monitoring and adjustment of neural recruitment, ensuring that the stimulus intensity remains within a therapeutic range, providing effective and comfortable neuromodulation despite electrode migration or postural changes.
Implementation Method 1
measurement circuitry configured to process a signal window sensed at the one or more sense electrodes subsequent to the delivered neural stimulus, the sensed signal window including an evoked neural response
Implementation Method 2
a stimulus source configured to provide a neural stimulus to be delivered via the one or more stimulus electrodes to a neural pathway of a patient in order to evoke a neural response on the neural pathway
Data Source
AI summary
Disclosed is an implantable device for controllably delivering a neural stimulus. The device comprises: a plurality of electrodes including one or more stimulus electrodes and one or more sense electrodes; a stimulus source configured to provide a neural stimulus to be delivered via the one or more stimulus electrodes to a neural pathway of a patient in order to evoke a neural response on the neural pathway; measurement circuitry configured to process a signal window sensed at the one or more sense electrodes subsequent to the delivered neural stimulus, the sensed signal window including an evoked neural response; and a control unit. The control unit is configured to: control the stimulus source to provide the neural stimulus according to a stimulus parameter; estimate, using a detector, a location of the evoked neural response within the sensed signal window; determine, based on the location of the evoked neural response within the sensed signal window, whether truncation of the evoked neural response by the sensed signal window is occurring; and mitigate, based on the determination, the truncation of the evoked neural response.