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Lam DV, Chin J, Brucker-Hahn MK, Settell M, Romanauski B, Verma N, Upadhye A, Deshmukh A, Skubal A, Nishiyama Y, Hao J, Lujan JL, Zhang S, Knudsen B, Blanz S, Lempka SF, Ludwig KA, Shoffstall AJ, Park HJ, Ellison ER, Zhang M, Lavrov I. The role of spinal cord neuroanatomy and the variances of epidurally evoked spinal responses. Bioelectron Med 2024; 10:17. [PMID: 39020366 PMCID: PMC11253499 DOI: 10.1186/s42234-024-00149-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 05/28/2024] [Indexed: 07/19/2024] Open
Abstract
BACKGROUND Spinal cord stimulation (SCS) has demonstrated multiple benefits in treating chronic pain and other clinical disorders related to sensorimotor dysfunctions. However, the underlying mechanisms are still not fully understood, including how electrode placement in relation to the spinal cord neuroanatomy influences epidural spinal recordings (ESRs). To characterize this relationship, this study utilized stimulation applied at various anatomical sections of the spinal column, including at levels of the intervertebral disc and regions correlating to the dorsal root entry zone. METHOD Two electrode arrays were surgically implanted into the dorsal epidural space of the swine. The stimulation leads were positioned such that the caudal-most electrode contact was at the level of a thoracic intervertebral segment. Intraoperative cone beam computed tomography (CBCT) images were utilized to precisely determine the location of the epidural leads relative to the spinal column. High-resolution microCT imaging and 3D-model reconstructions of the explanted spinal cord illustrated precise positioning and dimensions of the epidural leads in relation to the surrounding neuroanatomy, including the spinal rootlets of the dorsal and ventral columns of the spinal cord. In a separate swine cohort, implanted epidural leads were used for SCS and recording evoked ESRs. RESULTS Reconstructed 3D-models of the swine spinal cord with epidural lead implants demonstrated considerable distinctions in the dimensions of a single electrode contact on a standard industry epidural stimulation lead compared to dorsal rootlets at the dorsal root entry zone (DREZ). At the intervertebral segment, it was observed that a single electrode contact may cover 20-25% of the DREZ if positioned laterally. Electrode contacts were estimated to be ~0.75 mm from the margins of the DREZ when placed at the midline. Furthermore, ventral rootlets were observed to travel in proximity and parallel to dorsal rootlets at this level prior to separation into their respective sides of the spinal cord. Cathodic stimulation at the level of the intervertebral disc, compared to an 'off-disc' stimulation (7 mm rostral), demonstrated considerable variations in the features of recorded ESRs, such as amplitude and shape, and evoked unintended motor activation at lower stimulation thresholds. This substantial change may be due to the influence of nearby ventral roots. To further illustrate the influence of rootlet activation vs. dorsal column activation, the stimulation lead was displaced laterally at ~2.88 mm from the midline, resulting in variances in both evoked compound action potential (ECAP) components and electromyography (EMG) components in ESRs at lower stimulation thresholds. CONCLUSION The results of this study suggest that the ECAP and EMG components of recorded ESRs can vary depending on small differences in the location of the stimulating electrodes within the spinal anatomy, such as at the level of the intervertebral segment. Furthermore, the effects of sub-centimeter lateral displacement of the stimulation lead from the midline, leading to significant changes in electrophysiological metrics. The results of this pilot study reveal the importance of the small displacement of the electrodes that can cause significant changes to evoked responses SCS. These results may provide further valuable insights into the underlying mechanisms and assist in optimizing future SCS-related applications.
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Affiliation(s)
- Danny V Lam
- Neural Lab, Abbott Neuromodulation, Plano, TX, USA
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Department of Veterans Affairs Medical Center, Advanced Platform Technology Center, Louis Stokes Cleveland, Cleveland, OH, USA
| | - Justin Chin
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Meagan K Brucker-Hahn
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
| | - Megan Settell
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, USA
| | - Ben Romanauski
- Department of Neurosurgery, Mayo Clinic, Rochester, MN, USA
| | | | - Aniruddha Upadhye
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Ashlesha Deshmukh
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
| | - Aaron Skubal
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
| | | | - Jian Hao
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - J Luis Lujan
- Department of Neurosurgery, Mayo Clinic, Rochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Simeng Zhang
- Neural Lab, Abbott Neuromodulation, Plano, TX, USA
| | - Bruce Knudsen
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
| | - Stephan Blanz
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
- University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Kip A Ludwig
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, USA
| | - Andrew J Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Department of Veterans Affairs Medical Center, Advanced Platform Technology Center, Louis Stokes Cleveland, Cleveland, OH, USA
| | | | | | | | - Igor Lavrov
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA.
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Parker SR, Calvert JS, Darie R, Jang J, Govindarajan LN, Angelino K, Chitnis G, Iyassu Y, Shaaya E, Fridley JS, Serre T, McLaughlin BL, Borton DA. An active electronic bidirectional interface for high resolution interrogation of the spinal cord. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596250. [PMID: 38853820 PMCID: PMC11160681 DOI: 10.1101/2024.05.29.596250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Epidural electrical stimulation (EES) has shown promise as both a clinical therapeutic tool and research aid in the study of nervous system function. However, available clinical paddles are limited to using a small number of contacts due to the burden of wires necessary to connect each contact to the therapeutic device. Here, we introduce for the first time the integration of a hermetic active electronic multiplexer onto the electrode paddle array itself, removing this interconnect limitation. We evaluated the chronic implantation of an active electronic 60-contact paddle (the HD64) on the lumbosacral spinal cord of two sheep. The HD64 was implanted for 13 months and 15 months, with no device-related malfunctions or adverse events. We identified increased selectivity in EES-evoked motor responses using dense stimulating bipoles. Further, we found that dense recording bipoles decreased the spatial correlation between channels during recordings. Finally, spatial electrode encoding enabled a neural network to accurately perform EES parameter inference for unseen stimulation electrodes, reducing training data requirements. A high-density EES paddle, containing active electronics safely integrated into neural interfaces, opens new avenues for the study of nervous system function and new therapies to treat neural injury and dysfunction.
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Brucker-Hahn MK, Zander HJ, Will AJ, Vallabh JC, Wolff JS, Dinsmoor DA, Lempka SF. Evoked compound action potentials during spinal cord stimulation: effects of posture and pulse width on signal features and neural activation within the spinal cord. J Neural Eng 2023; 20:046028. [PMID: 37531954 DOI: 10.1088/1741-2552/aceca4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 08/01/2023] [Indexed: 08/04/2023]
Abstract
Objective.Evoked compound action potential (ECAP) recordings have emerged as a quantitative measure of the neural response during spinal cord stimulation (SCS) to treat pain. However, utilization of ECAP recordings to optimize stimulation efficacy requires an understanding of the factors influencing these recordings and their relationship to the underlying neural activation.Approach.We acquired a library of ECAP recordings from 56 patients over a wide assortment of postures and stimulation parameters, and then processed these signals to quantify several aspects of these recordings (e.g., ECAP threshold (ET), amplitude, latency, growth rate). We compared our experimental findings against a computational model that examined the effect of variable distances between the spinal cord and the SCS electrodes.Main results.Postural shifts strongly influenced the experimental ECAP recordings, with a 65.7% lower ET and 178.5% higher growth rate when supine versus seated. The computational model exhibited similar trends, with a 71.9% lower ET and 231.5% higher growth rate for a 2.0 mm cerebrospinal fluid (CSF) layer (representing a supine posture) versus a 4.4 mm CSF layer (representing a prone posture). Furthermore, the computational model demonstrated that constant ECAP amplitudes may not equate to a constant degree of neural activation.Significance.These results demonstrate large variability across all ECAP metrics and the inability of a constant ECAP amplitude to provide constant neural activation. These results are critical to improve the delivery, efficacy, and robustness of clinical SCS technologies utilizing these ECAP recordings to provide closed-loop stimulation.
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Affiliation(s)
- Meagan K Brucker-Hahn
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States of America
| | - Hans J Zander
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States of America
| | - Andrew J Will
- Twin Cities Pain Clinic, Edina, MN, United States of America
| | - Jayesh C Vallabh
- Ohio State Wexner Medical Center, Columbus, OH, United States of America
| | - Jason S Wolff
- iSpine Clinics, Maple Grove, MN, United States of America
| | | | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States of America
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, United States of America
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Panskus R, Holzapfel L, Serdijn WA, Giagka V. On the Stimulation Artifact Reduction during Electrophysiological Recording of Compound Nerve Action Potentials . ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-5. [PMID: 38083005 DOI: 10.1109/embc40787.2023.10341179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Recording neuronal activity triggered by electrical impulses is a powerful tool in neuroscience research and neural engineering. It is often applied in acute electrophysiological experimental settings to record compound nerve action potentials. However, the elicited neural response is often distorted by electrical stimulus artifacts, complicating subsequent analysis. In this work, we present a model to better understand the effect of the selected amplifier configuration and the location of the ground electrode in a practical electrophysiological nerve setup. Simulation results show that the stimulus artifact can be reduced by more than an order of magnitude if the placement of the ground electrode, its impedance, and the amplifier configuration are optimized. We experimentally demonstrate the effects in three different settings, in-vivo and in-vitro.
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Berfelo T, van den Berg B, Krabbenbos IP, de Beer MF, Buitenweg JR. Exploring Psychophysical and Neurophysiological Responses to Intra-Epidermal Electrical Stimuli in Patients With Persistent Spinal Pain Syndrome Type 2 with a Spinal Cord Stimulator. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38083629 DOI: 10.1109/embc40787.2023.10340377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
There is a lack of measures that provide insights into how spinal cord stimulation (SCS) modulates nociceptive function in patients with persistent spinal pain syndrome type 2 (PSPS-T2). Recently, we observed altered nociceptive detection thresholds (NDTs) in response to intra-epidermal electrical stimulation (IES) on the feet of PSPS-T2 patients when dorsal root ganglion stimulation was turned on. Furthermore, we observed altered NDTs and evoked potentials (EPs) in response to IES on the hands of PSPS-T2 patients. To explore whether EPs were obstructed by SCS artifacts, we applied IES twice to the hands of patients with SCS turned on (SCS-ON/ON group). To explore possible confounding effects of SCS outside the stimulated area, we repeated IES on the hands of these patients, once with SCS turned off and subsequently once with SCS turned on (SCS-OFF/ON group). The results demonstrated that EPs were not obstructed by SCS artifacts. Additionally, NDTs and EPs did not significantly change between measurements in the SCS-ON/ON and the SCS-OFF/ON groups. Therefore, the results suggested that possible confounding effects of SCS outside the nociceptive system did not interfere with the detection task performance. This work warrants further exploration of NDT-EP phenomena in response to IES at the painful feet of patients.Clinical Relevance-This work contributes to developing a clinical tool to explore psychophysical and neurophysiological biomarkers for observing modulating effects of SCS in patients with PSPS-T2.
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Sharma M, Bhaskar V, Yang L, FallahRad M, Gebodh N, Zhang T, Esteller R, Martin J, Bikson M. Novel Evoked Synaptic Activity Potentials (ESAPs) Elicited by Spinal Cord Stimulation. eNeuro 2023; 10:ENEURO.0429-22.2023. [PMID: 37130780 PMCID: PMC10198607 DOI: 10.1523/eneuro.0429-22.2023] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 04/05/2023] [Accepted: 04/11/2023] [Indexed: 05/04/2023] Open
Abstract
Spinal cord stimulation (SCS) evokes fast epidural evoked compound action potential (ECAP) that represent activity of dorsal column axons, but not necessarily a spinal circuit response. Using a multimodal approach, we identified and characterized a delayed and slower potential evoked by SCS that reflects synaptic activity within the spinal cord. Anesthetized female Sprague Dawley rats were implanted with an epidural SCS lead, epidural motor cortex stimulation electrodes, an epidural spinal cord recording lead, an intraspinal penetrating recording electrode array, and intramuscular electromyography (EMG) electrodes in the hindlimb and trunk. We stimulated the motor cortex or the epidural spinal cord and recorded epidural, intraspinal, and EMG responses. SCS pulses produced characteristic propagating ECAPs (composed of P1, N1, and P2 waves with latencies <2 ms) and an additional wave ("S1") starting after the N2. We verified the S1-wave was not a stimulation artifact and was not a reflection of hindlimb/trunk EMG. The S1-wave has a distinct stimulation-intensity dose response and spatial profile compared with ECAPs. 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX; a selective competitive antagonist of AMPA receptors (AMPARs)] significantly diminished the S1-wave, but not ECAPs. Furthermore, cortical stimulation, which did not evoke ECAPs, produced epidurally detectable and CNQX-sensitive responses at the same spinal sites, confirming epidural recording of an evoked synaptic response. Finally, applying 50-Hz SCS resulted in dampening of S1-wave but not ECAPs. Therefore, we hypothesize that the S1-wave is synaptic in origin, and we term the S1-wave type responses: evoked synaptic activity potentials (ESAPs). The identification and characterization of epidurally recorded ESAPs from the dorsal horn may elucidate SCS mechanisms.
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Affiliation(s)
- Mahima Sharma
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
| | - Vividha Bhaskar
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
| | - Lillian Yang
- Department of Molecular, Cellular and Biomedical Sciences, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
| | - Mohamad FallahRad
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
| | - Nigel Gebodh
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
| | - Tianhe Zhang
- Boston Scientific Neuromodulation Research and Advanced Concepts, Valencia, CA 91355
| | - Rosana Esteller
- Boston Scientific Neuromodulation Research and Advanced Concepts, Valencia, CA 91355
| | - John Martin
- Department of Molecular, Cellular and Biomedical Sciences, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
| | - Marom Bikson
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of the City University of New York, City College Center for Discovery and Innovation, New York, NY 10031
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Verma N, Romanauski B, Lam D, Lujan L, Blanz S, Ludwig K, Lempka S, Shoffstall A, Knudson B, Nishiyama Y, Hao J, Park HJ, Ross E, Lavrov I, Zhang M. Characterization and applications of evoked responses during epidural electrical stimulation. Bioelectron Med 2023; 9:5. [PMID: 36855060 PMCID: PMC9976490 DOI: 10.1186/s42234-023-00106-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/08/2023] [Indexed: 03/02/2023] Open
Abstract
BACKGROUND Epidural electrical stimulation (EES) of the spinal cord has been FDA approved and used therapeutically for decades. However, there is still not a clear understanding of the local neural substrates and consequently the mechanism of action responsible for the therapeutic effects. METHOD Epidural spinal recordings (ESR) are collected from the electrodes placed in the epidural space. ESR contains multi-modality signal components such as the evoked neural response (due to tonic or BurstDR™ waveforms), evoked muscle response, stimulation artifact, and cardiac response. The tonic stimulation evoked compound action potential (ECAP) is one of the components in ESR and has been proposed recently to measure the accumulative local potentials from large populations of neuronal fibers during EES. RESULT Here, we first review and investigate the referencing strategies, as they apply to ECAP component in ESR in the domestic swine animal model. We then examine how ECAP component can be used to sense lead migration, an adverse outcome following lead placement that can reduce therapeutic efficacy. Lastly, we show and isolate concurrent activation of local back and leg muscles during EES, demonstrating that the ESR obtained from the recording contacts contain both ECAP and EMG components. CONCLUSION These findings may further guide the implementation of recording and reference contacts in an implantable EES system and provide preliminary evidence for the utility of ECAP component in ESR to detect lead migration. We expect these results to facilitate future development of EES methodology and implementation of use of different components in ESR to improve EES therapy.
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Affiliation(s)
- Nishant Verma
- Abbott Neuromodulation, 6901 Preston Rd, Plano, TX, 75024, USA
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
| | - Ben Romanauski
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
| | - Danny Lam
- Abbott Neuromodulation, 6901 Preston Rd, Plano, TX, 75024, USA
| | - Luis Lujan
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Stephan Blanz
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
- University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Kip Ludwig
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, USA
| | - Scott Lempka
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- APT Center, Louis Stokes Cleveland VA Medical Center, OH, Cleveland, USA
- Department of Biomedical Engineering, Department of Anesthesiology, Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
| | - Andrew Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- APT Center, Louis Stokes Cleveland VA Medical Center, OH, Cleveland, USA
| | - Bruce Knudson
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, USA
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
| | - Yuichiro Nishiyama
- Department of Neurology, Department of Physiology and Biomedical Engineering, Mayo Clinic, 500 First Street SW, Rochester, MN, 55905, USA
| | - Jian Hao
- Department of Neurology, Department of Physiology and Biomedical Engineering, Mayo Clinic, 500 First Street SW, Rochester, MN, 55905, USA
| | - Hyun-Joo Park
- Abbott Neuromodulation, 6901 Preston Rd, Plano, TX, 75024, USA
| | - Erika Ross
- Abbott Neuromodulation, 6901 Preston Rd, Plano, TX, 75024, USA
| | - Igor Lavrov
- Department of Neurology, Department of Physiology and Biomedical Engineering, Mayo Clinic, 500 First Street SW, Rochester, MN, 55905, USA.
| | - Mingming Zhang
- Abbott Neuromodulation, 6901 Preston Rd, Plano, TX, 75024, USA.
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Ramadan A, König SD, Zhang M, Ross EK, Herman A, Netoff TI, Darrow DP. Methods and system for recording human physiological signals from implantable leads during spinal cord stimulation. FRONTIERS IN PAIN RESEARCH 2023; 4:1072786. [PMID: 36937564 PMCID: PMC10020336 DOI: 10.3389/fpain.2023.1072786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 01/23/2023] [Indexed: 03/06/2023] Open
Abstract
Objectives This article presents a method-including hardware configuration, sampling rate, filtering settings, and other data analysis techniques-to measure evoked compound action potentials (ECAPs) during spinal cord stimulation (SCS) in humans with externalized percutaneous electrodes. The goal is to provide a robust and standardized protocol for measuring ECAPs on the non-stimulation contacts and to demonstrate how measured signals depend on hardware and processing decisions. Methods Two participants were implanted with percutaneous leads for the treatment of chronic pain with externalized leads during a trial period for stimulation and recording. The leads were connected to a Neuralynx ATLAS system allowing us to simultaneously stimulate and record through selected electrodes. We examined different hardware settings, such as online filters and sampling rate, as well as processing techniques, such as stimulation artifact removal and offline filters, and measured the effects on the ECAPs metrics: the first negative peak (N1) time and peak-valley amplitude. Results For accurate measurements of ECAPs, the hardware sampling rate should be least at 8 kHz and should use a high pass filter with a low cutoff frequency, such as 0.1 Hz, to eliminate baseline drift and saturation (railing). Stimulation artifact removal can use a double exponential or a second-order polynomial. The polynomial fit is 6.4 times faster on average in computation time than the double exponential, while the resulting ECAPs' N1 time and peak-valley amplitude are similar between the two. If the baseline raw measurement drifts with stimulation, a median filter with a 100-ms window or a high pass filter with an 80-Hz cutoff frequency preserves the ECAPs. Conclusions This work is the first comprehensive analysis of hardware and processing variations on the observed ECAPs from SCS leads. It sets recommendations to properly record and process ECAPs from the non-stimulation contacts on the implantable leads.
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Affiliation(s)
- Ahmed Ramadan
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States
| | - Seth D. König
- Department of Neurosurgery, University of Minnesota, Minneapolis, MN, United States
- Department of Psychiatry and Behavioral Sciences, University of Minnesota, Minneapolis, MN, United States
| | - Mingming Zhang
- Clinical and Applied Research, Abbott Neuromodulation, Plano, TX, United States
- Correspondence: David P. Darrow Mingming Zhang
| | - Erika K. Ross
- Clinical and Applied Research, Abbott Neuromodulation, Plano, TX, United States
| | - Alexander Herman
- Department of Psychiatry and Behavioral Sciences, University of Minnesota, Minneapolis, MN, United States
| | - Theoden I. Netoff
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States
| | - David P. Darrow
- Department of Neurosurgery, University of Minnesota, Minneapolis, MN, United States
- Correspondence: David P. Darrow Mingming Zhang
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Using evoked compound action potentials to quantify differential neural activation with burst and conventional, 40 Hz spinal cord stimulation in ovines. Pain Rep 2022; 7:e1047. [DOI: 10.1097/pr9.0000000000001047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 08/22/2022] [Accepted: 09/14/2022] [Indexed: 11/13/2022] Open
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Sevcencu C. Single-interface bioelectronic medicines - concept, clinical applications and preclinical data. J Neural Eng 2022; 19. [PMID: 35533654 DOI: 10.1088/1741-2552/ac6e08] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 05/08/2022] [Indexed: 11/12/2022]
Abstract
Presently, large groups of patients with various diseases are either intolerant, or irresponsive to drug therapies and also intractable by surgery. For several diseases, one option which is available for such patients is the implantable neurostimulation therapy. However, lacking closed-loop control and selective stimulation capabilities, the present neurostimulation therapies are not optimal and are therefore used as only "third" therapeutic options when a disease cannot be treated by drugs or surgery. Addressing those limitations, a next generation class of closed-loop controlled and selective neurostimulators generically named bioelectronic medicines seems within reach. A sub-class of such devices is meant to monitor and treat impaired functions by intercepting, analyzing and modulating neural signals involved in the regulation of such functions using just one neural interface for those purposes. The primary objective of this review is to provide a first broad perspective on this type of single-interface devices for bioelectronic therapies. For this purpose, the concept, clinical applications and preclinical studies for further developments with such devices are here analyzed in a narrative manner.
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Affiliation(s)
- Cristian Sevcencu
- National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, Cluj-Napoca, 400293, ROMANIA
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Vallejo R, Chakravarthy K, Will A, Trutnau K, Dinsmoor D. A New Direction for Closed-Loop Spinal Cord Stimulation: Combining Contemporary Therapy Paradigms with Evoked Compound Action Potential Sensing. J Pain Res 2022; 14:3909-3918. [PMID: 35002310 PMCID: PMC8721159 DOI: 10.2147/jpr.s344568] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 12/21/2021] [Indexed: 01/01/2023] Open
Abstract
Spinal cord stimulation (SCS) utilizes the delivery of mild electrical pulses via epidural electrodes placed on the dorsal side of the spinal cord, typically to treat chronic pain. The first clinical use of SCS involved the delivery of paresthesia inducing, low-frequency waveforms to the neural targets corresponding to the painful areas. Contemporary SCS therapies now leverage novel therapeutic pathways to limit paresthesia and deliver superior clinical outcomes. Historically, SCS has largely been delivered with fixed stimulation parameters. This approach, referred to as open-loop (OL) SCS, does not account for the fluctuations in spacing—driven by postural changes and activity—between the electrodes and the cord. These fluctuations result in variability in the delivered dose and the volume of tissue activation (VTA) that manifests with each stimulation pulse. Inconsistent dosing may lead to suboptimal therapeutic efficacy and durability. To address this clinical need, closed-loop (CL) SCS systems have been developed to automatically adjust stimulation parameters to compensate for this variability. The evoked compound action potential (ECAP), a biopotential generated by the synchronous activation of dorsal column fibers, is indicative of the VTA resulting from the stimulation pulse. The ECAP may be utilized as a control signal in CL SCS systems to adjust stimulation parameters to reduce variability in the ECAP, and in turn, variability in the VTA. While investigational CL SCS systems with ECAP sensing have so far focused solely on managing paresthesia-based SCS, such systems must also incorporate the stimulation approaches that now define the contemporary clinical practice of SCS. Accordingly, we describe here a flexible, next-generation framework for neural responsive SCS that blends science-based methodologies for pain management with real-time CL control for biophysical variation. We conclude with a clinical example of such a system and the associated performance characteristics.
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Affiliation(s)
| | - Krishnan Chakravarthy
- Anesthesiology and Pain Management, University of California San Diego, San Diego, CA, USA
| | | | | | - David Dinsmoor
- Neuromodulation Research & Technology, Medtronic plc, Minneapolis, MN, USA
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Chakravarthy K, FitzGerald J, Will A, Trutnau K, Corey R, Dinsmoor D, Litvak L. A Clinical Feasibility Study of Spinal Evoked Compound Action Potential Estimation Methods. Neuromodulation 2022; 25:75-84. [PMID: 35041590 DOI: 10.1111/ner.13510] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/18/2021] [Accepted: 07/06/2021] [Indexed: 11/28/2022]
Abstract
OBJECTIVES Spinal cord stimulation (SCS) is a treatment for chronic neuropathic pain. Recently, SCS has been enhanced further with evoked compound action potential (ECAP) sensing. Characteristics of the ECAP, if appropriately isolated from concurrent stimulation artifact (SA), may be used to control, and aid in the programming of, SCS systems. Here, we characterize the sensitivity of the ECAP growth curve slope (S) to both neural response (|Sresp|) and SA contamination (|Sart|) for four spinal ECAP estimation methods with a novel performance measure (|Sresp/Sart|). MATERIALS AND METHODS We collected a library of 112 ECAP and associated artifact recordings with swept stimulation amplitudes from 14 human subjects. We processed the signals to reduce SA from these recordings by applying one of three schemes: a simple high-pass (HP) filter, subtracting an artifact model (AM) consisting of decaying exponential and linear components, or applying a template correlation method consisting of a triangularly weighted sinusoid. We compared these against each other and to P2-N1, a standard method of measuring ECAP amplitude. We then fit the ECAP estimates from each method with a function representing the growth curve and calculated the Sresp and Sart parameters following the fit. RESULTS Any SA reduction scheme selected may result in under- or overestimation of neural activation or misclassification of SA as ECAP. In these experiments, the ratio of neural signal preservation to SA misclassification (|Sresp/Sart|) on the ECAP estimate was superior (p < 0.05) with the HP and AM schemes relative to the others. CONCLUSIONS This work represents the first comprehensive assessment of spinal ECAP estimation schemes. Understanding the clinically relevant sensitivities of these schemes is increasingly important, particularly with closed-loop SCS systems using ECAP as a feedback control variable where misclassification of artifact as neural signal may lead to suboptimal therapy adjustments.
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Affiliation(s)
| | - James FitzGerald
- Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK
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Pilitsis JG, Chakravarthy KV, Will AJ, Trutnau KC, Hageman KN, Dinsmoor DA, Litvak LM. The Evoked Compound Action Potential as a Predictor for Perception in Chronic Pain Patients: Tools for Automatic Spinal Cord Stimulator Programming and Control. Front Neurosci 2021; 15:673998. [PMID: 34335157 PMCID: PMC8320888 DOI: 10.3389/fnins.2021.673998] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 06/21/2021] [Indexed: 12/21/2022] Open
Abstract
Objectives Spinal cord stimulation (SCS) is a drug free treatment for chronic pain. Recent technological advances have enabled sensing of the evoked compound action potential (ECAP), a biopotential that represents neural activity elicited from SCS. The amplitudes of many SCS paradigms – both sub- and supra-threshold – are programmed relative to the patient’s perception of SCS. The objective of this study, then, is to elucidate relationships between the ECAP and perception thresholds across posture and SCS pulse width. These relationships may be used for the automatic control and perceptually referenced programming of SCS systems. Methods ECAPs were acquired from 14 subjects across a range of postures and pulse widths with swept amplitude stimulation. Perception (PT) and discomfort (DT) thresholds were recorded. A stimulation artifact reduction scheme was employed, and growth curves were constructed from the sweeps. An estimate of the ECAP threshold (ET), was calculated from the growth curves using a novel approach. Relationships between ET, PT, and DT were assessed. Results ETs were estimated from 112 separate growth curves. For the postures and pulse widths assessed, the ET tightly correlated with both PT (r = 0.93; p < 0.0001) and DT (r = 0.93; p < 0.0001). The median accuracy of ET as a predictor for PT across both posture and pulse width was 0.5 dB. Intra-subject, ECAP amplitudes at DT varied up to threefold across posture. Conclusion We provide evidence that the ET varies across both different positions and varying pulse widths and suggest that this variance may be the result of postural dependence of the recording electrode-tissue spacing. ET-informed SCS holds promise as a tool for SCS parameter configuration and may offer more accuracy over alternative approaches for neural and perceptual control in closed loop SCS systems.
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Affiliation(s)
- Julie G Pilitsis
- Department of Neurosurgery, Albany Medical Center, Albany, NY, United States
| | - Krishnan V Chakravarthy
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA, United States
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