Pre-pulsing Neurostimulation for Selective Nerve Fiber Activation
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Solution Overview
Problem
Current neurostimulation systems face challenges in selectively stimulating target nerve tissue while minimizing the activation of non-target tissue, particularly due to the differences in nerve fiber diameters and orientations, leading to unwanted side effects such as involuntary motor movements.
Innovation Solution
The use of sub-threshold hyperpolarizing and depolarizing conditioning pulses of short duration, applied via separate electrodes, to modify the excitability of nerve tissue, allowing for more precise stimulation of dorsal column fibers over dorsal root fibers, thereby increasing the stimulation threshold of non-target tissue and reducing side effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional neurostimulation is used to stimulate target nerve tissue, then therapeutic benefit is achieved, but non-target nerve tissue is also activated causing side effects
Solution Approach 1:
A sub-threshold conditioning pulse is applied before the main stimulation pulse to modify the excitability state of nerve fibers. This preliminary action selectively raises the threshold of non-target dorsal root fibers, preventing their activation during the subsequent therapeutic stimulation while allowing target dorsal column fibers to be stimulated effectively.
Solution Approach 2:
The patent utilizes changes in nerve fiber excitability parameters through the conditioning pulse. By applying a sub-threshold pulse with specific amplitude and duration parameters, the membrane potential of nerve fibers is temporarily altered, creating a refractory state that selectively affects non-target fibers based on their diameter and orientation characteristics.
2Reliability
If long duration conditioning pulses are used to increase selectivity, then non-target tissue threshold is increased, but stimulation pulse duration must be extended reducing treatment efficiency
Solution Approach 1:
The patent identifies optimal parameter ranges for the conditioning pulse: amplitude between 0.1-2.0 mA and duration between 10-200 microseconds. These parameter changes create sufficient threshold elevation in non-target fibers without requiring long pulse durations, thereby maintaining high treatment efficiency while achieving selective stimulation.
Solution Approach 2:
The sub-threshold conditioning pulse applies a partial action that is sufficient to modify excitability but insufficient to directly activate non-target fibers. This partial action elevates the threshold just enough to prevent unwanted activation during therapeutic stimulation, avoiding the need for excessive pulse duration or amplitude.
3Reliability
If higher stimulation amplitude is used to ensure target fiber activation, then therapeutic effect is improved, but non-target fiber activation increases causing more side effects
Solution Approach 1:
The conditioning pulse is delivered immediately before the therapeutic stimulation pulse, creating a temporary refractory state in non-target dorsal root fibers. This preliminary modification of excitability allows the subsequent therapeutic pulse to activate target dorsal column fibers at effective amplitudes without causing unwanted activation of non-target fibers that would produce motor side effects.
Solution Approach 2:
The sub-threshold conditioning pulse applies a counteracting influence that raises the excitation threshold of non-target fibers in opposition to the activating effect of the therapeutic pulse. This preliminary anti-action prevents the harmful activation of motor fibers while allowing the therapeutic stimulation to proceed at optimal amplitudes for pain relief.
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 effectively increases the stimulation threshold of non-target tissue, allowing for more selective and efficient stimulation of target nerve fibers, even with short duration stimulation pulses, thereby reducing unwanted side effects and improving therapeutic efficacy.
Implementation Method 1
conveying a sub-threshold, hyperpolarizing, conditioning pre-pulse from the electrode(s) to render a first region of the tissue less excitable to stimulation
Implementation Method 2
conveying a depolarizing stimulation pulse from the electrode(s) to stimulate a second different region of the tissue
Data Source
AI summary
A method and neurostimulation system of providing therapy to a patient is provided. At least one electrode is place in contact with tissue of a patient. A sub-threshold, hyperpolarizing, conditioning pre-pulse (e.g., an anodic pulse) is conveyed from the electrode(s) to render a first region of the tissue (e.g., dorsal root fibers) less excitable to stimulation, and a depolarizing stimulation pulse (e.g., a cathodic pulse) is conveyed from the electrode(s) to stimulate a second different region of the tissue (e.g., dorsal column fibers). The conditioning pre-pulse has a relatively short duration (e.g., less than 200 μs).