Implanted Electrode Array Timing for Selective Neural Recruitment
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Solution Overview
Problem
Existing neuromodulation systems face challenges in maintaining effective and comfortable neural recruitment by recruiting specific fiber classes while avoiding unwanted side effects due to electrode migration and postural changes, which alter neural response patterns.
Innovation Solution
A method and device that apply a sequence of neural stimuli, with each stimulus timed during the refractory period of the previous one, to decorrelate fiber responses and achieve therapeutic effects while minimizing psychophysical side effects, using an implanted electrode array and control unit to optimize stimulus parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous stimuli are applied at high frequency (e.g., 100 Hz) to sustain pain relief effects, then therapeutic efficacy is improved, but psychophysical side effects increase and comfort decreases
Solution Approach 1:
The patent applies periodic neural stimuli with specific inter-stimulus intervals that target the refractory period of neural fibers. By delivering stimuli in a periodic sequence rather than continuous high-frequency activation, the system maintains therapeutic efficacy through rhythmic recruitment of Aβ fibers while allowing sufficient recovery time to minimize psychophysical side effects and patient discomfort.
Solution Approach 2:
The system dynamically adjusts stimulus parameters including inter-stimulus intervals, pulse amplitudes, and electrode selection based on measured compound action potential (CAP) amplitudes and patient feedback. This dynamic adaptation allows optimization of therapeutic effect while minimizing side effects by responding to changing neural recruitment patterns and patient comfort levels in real-time.
2Reliability
If electrode array is implanted to stimulate dorsal column, then neural recruitment is improved, but electrode migration and postural changes cause loss of selective fiber class recruitment
Solution Approach 1:
The system employs continuous feedback control by measuring compound action potential (CAP) amplitudes from recorded neural responses and using these measurements to adjust subsequent stimulus parameters. This closed-loop feedback mechanism compensates for electrode migration and postural changes by detecting shifts in neural recruitment patterns and adapting stimulus delivery to maintain selective Aβ fiber activation despite physical displacement.
Solution Approach 2:
The patent changes multiple stimulus parameters including inter-stimulus intervals, pulse amplitudes, pulse widths, and electrode combinations based on measured CAP amplitudes and identified fiber class recruitment patterns. By dynamically modifying these parameters in response to detected changes in neural response, the system maintains selective recruitment of target fiber classes despite electrode migration or patient movement.
3Reliability
If stimulus amplitude is increased to recruit more fibers, then therapeutic effect is improved, but unwanted side effects from recruiting non-target fiber classes increase
Solution Approach 1:
By using periodic stimuli with inter-stimulus intervals matching the refractory period of Aβ fibers, the system achieves cumulative recruitment of target fibers through repeated activation cycles without requiring high single-pulse amplitudes. This temporal pattern allows selective recruitment of large-diameter Aβ fibers while avoiding activation of smaller Aδ and C fibers that cause unwanted sensations, thereby improving therapeutic effect without increasing side effects.
Solution Approach 2:
The system dynamically adjusts stimulus amplitude based on measured CAP amplitudes and identified recruitment thresholds for different fiber classes. By adapting amplitude in real-time according to actual neural response rather than using fixed high amplitudes, the system maintains effective therapeutic recruitment of Aβ fibers while minimizing activation of non-target fiber classes that produce harmful side effects.
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
This approach enhances selective neural recruitment, reducing unwanted side effects by decorrelating fiber responses, allowing for adaptive control of stimuli to maintain therapeutic efficacy across varying postures and electrode positions.
Implementation Method 1
An electrical pulse applied to the dorsal column by an electrode causes the depolarisation of neurons, and generation of propagating action potentials
Implementation Method 2
generation of propagating action potentials. The fibres being stimulated in this way inhibit the transmission of pain
Implementation Method 3
measurement of a compound action potential by using one or more electrodes implanted proximal to the neural pathway
Data Source
AI summary
A method of applying a neural stimulus with an implanted electrode array involves applying a sequence of stimuli configured to yield a therapeutic effect while suppressing psychophysical side effects. The stimuli sequence is configured such that a first stimulus recruits a portion of the fibre population, and a second stimulus is delivered within the refractory period following the first stimulus and the second stimulus being configured to recruit a further portion of the fibre population. Using an electrode array and suitable relative timing of the stimuli, ascending or descending volleys of evoked responses can be selectively synchronised or desynchronised to give directional control over responses evoked.