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Gransier R, Carlyon RP, Richardson ML, Middlebrooks JC, Wouters J. Artifact removal by template subtraction enables recordings of the frequency following response in cochlear-implant users. Sci Rep 2024; 14:6158. [PMID: 38486005 PMCID: PMC10940306 DOI: 10.1038/s41598-024-56047-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 03/01/2024] [Indexed: 03/18/2024] Open
Abstract
Electrically evoked frequency-following responses (eFFRs) provide insight in the phase-locking ability of brainstem of cochlear-implant (CI) users. eFFRs can potentially be used to gain insight in the individual differences in the biological limitation on temporal encoding of the electrically stimulated auditory pathway, which can be inherent to the electrical stimulation itself and/or the degenerative processes associated with hearing loss. One of the major challenge of measuring eFFRs in CI users is the process of isolating the stimulation artifact from the neural response, as both the response and the artifact overlap in time and have similar frequency characteristics. Here we introduce a new artifact removal method based on template subtraction that successfully removes the stimulation artifacts from the recordings when CI users are stimulated with pulse trains from 128 to 300 pulses per second in a monopolar configuration. Our results show that, although artifact removal was successful in all CI users, the phase-locking ability of the brainstem to the different pulse rates, as assessed with the eFFR differed substantially across participants. These results show that the eFFR can be measured, free from artifacts, in CI users and that they can be used to gain insight in individual differences in temporal processing of the electrically stimulated auditory pathway.
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Affiliation(s)
- Robin Gransier
- ExpORL, Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - Robert P Carlyon
- Cambridge Hearing Group, MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, UK
| | - Matthew L Richardson
- Department of Otolaryngology, University of California at Irvine, Irvine, CA, USA
- Center for Hearing Research, University of California at Irvine, Irvine, CA, USA
| | - John C Middlebrooks
- Department of Otolaryngology, University of California at Irvine, Irvine, CA, USA
- Center for Hearing Research, University of California at Irvine, Irvine, CA, USA
- Departments of Neurobiology and Behavior, Biomedical Engineering, Cognitive Sciences, University of California at Irvine, Irvine, CA, USA
| | - Jan Wouters
- ExpORL, Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium.
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Goudelocke C, Jungbauer Nikolas LM, Bittner KC, Offutt SJ, Miller AE, Slopsema JP. Sensing in Sacral Neuromodulation: A Feasibility Study in Subjects With Urinary Incontinence and Retention. Neuromodulation 2024; 27:392-398. [PMID: 37589643 DOI: 10.1016/j.neurom.2023.07.002] [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: 03/30/2023] [Revised: 06/27/2023] [Accepted: 07/06/2023] [Indexed: 08/18/2023]
Abstract
OBJECTIVES Sacral neuromodulation (SNM) therapy standard of care relies on visual-motor responses and patient-reported sensory responses in deciding optimized lead placement and programming. Automatic detection of stimulation responses could offer a simple, consistent indicator for optimizing SNM. The purpose of this study was to measure and characterize sacral evoked responses (SERs) resulting from sacral nerve stimulation using a commercial, tined SNM lead. MATERIALS AND METHODS A custom external research system with stimulation and sensing hardware was connected to the percutaneous extension of an implanted lead during a staged (tined lead) evaluation for SNM. The system collected SER recordings across a range of prespecified stimulation settings (electrode configuration combinations for bipolar stimulation and bipolar sensing) during intraoperative and postoperative sessions in 21 subjects with overactive bladder (OAB) and nonobstructive urinary retention (NOUR). Motor and sensory thresholds were collected during the same sessions. RESULTS SERs were detected in all 21 subjects. SER morphology (number of peaks, magnitude, and timing) varied across electrode configurations within and across subjects. Among subjects and electrode configurations tested, recordings contained SERs at motor threshold and/or sensory threshold in 75% to 80% of subjects. CONCLUSIONS This study confirmed that implanted SNM leads can be used to directly record SERs elicited by stimulation in subjects with OAB and NOUR. SERs were readily detectable at typical SNM stimulation settings and procedural time points. Using these SERs as possible objective measures of SNM response has the capability to automate patient-specific SNM therapy, potentially providing consistent lead placement, programming, and/or closed-loop therapy.
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Affiliation(s)
- Colin Goudelocke
- Department of Urology, Ochsner Medical Center, New Orleans, LA, USA
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Skidmore J, Yuan Y, He S. A new method for removing artifacts from recordings of the electrically evoked compound action potential: Single-pulse stimulation. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.01.17.24301435. [PMID: 38293121 PMCID: PMC10827261 DOI: 10.1101/2024.01.17.24301435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
This report presents a new method for removing electrical artifact contamination from the electrically evoked compound action potential (eCAP) evoked by single cathodic-leading, biphasic-pulse stimulation. The development of the new method is motivated by results recorded in human cochlear implant (CI) users showing that the fundamental assumption of the classic forward masking artifact rejection technique is violated in up to 45% of cases tested at high stimulation levels when using default stimulation parameters. Subsequently, the new method developed based on the discovery that a hyperbola best characterizes the artifacts created during stimulation and recording is described. The eCAP waveforms obtained using the new method are compared to those recorded using the classic forward masking technique. The results show that eCAP waveforms obtained using both methods are comparable when the fundamental assumption of the classic forward masking technique is met. In contrast, eCAP amplitudes obtained using the two methods are significantly different when the fundamental assumption of the classic forward masking technique is violated, with greater differences in the eCAP amplitude for greater assumption violations. The new method also has excellent test-retest reliability (Intraclass correlation > 0.98). Overall, the new method is a viable alternative to the classic forward masking technique for obtaining artifact-free eCAPs evoked by single-pulse stimulation in CI users.
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Affiliation(s)
- Jeffrey Skidmore
- Department of Otolaryngology – Head and Neck Surgery, The Ohio State University, 915 Olentangy River Road, Columbus, OH 43212, USA
| | - Yi Yuan
- Department of Otolaryngology – Head and Neck Surgery, The Ohio State University, 915 Olentangy River Road, Columbus, OH 43212, USA
| | - Shuman He
- Department of Otolaryngology – Head and Neck Surgery, The Ohio State University, 915 Olentangy River Road, Columbus, OH 43212, USA
- Department of Audiology, Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH 43205, USA
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North RB, Sung JH, Matthews LA, Zander HJ, Lempka SF. Postural Changes in Spinal Cord Stimulation Thresholds: Current and Voltage Sources. Neuromodulation 2024; 27:178-182. [PMID: 37804279 DOI: 10.1016/j.neurom.2023.08.006] [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: 07/09/2023] [Revised: 07/27/2023] [Accepted: 08/04/2023] [Indexed: 10/09/2023]
Abstract
OBJECTIVE Spinal cord stimulation (SCS) thresholds are known to change with body position; however, these changes have not been fully characterized for both "constant-voltage" and "constant-current" pulse generators. This study aimed to evaluate and quantify changes in psychophysical thresholds resulting from postural changes that may affect both conventional paresthesia-based SCS and novel paresthesia-free SCS technologies. MATERIALS AND METHODS We measured perceptual, usage, and discomfort thresholds in four body positions (prone, supine, sitting, standing) in 149 consecutive patients, with temporary lower thoracic percutaneous epidural electrodes placed for treating persistent low back and leg pain. We trialed 119 patients with constant-voltage stimulators and 30 patients with constant-current stimulators. RESULTS Moving from supine to the sitting, standing, or prone positions caused all three thresholds (perceptual, usage, and discomfort) to increase by 22% to 34% for constant-voltage stimulators and by 44% to 82% for constant-current stimulators. Changing from a seated to a supine position caused stimulation to exceed discomfort threshold significantly more often for constant-current (87%) than for constant-voltage (63%) stimulators (p = 0.01). CONCLUSIONS Posture-induced changes in SCS thresholds occurred consistently as patients moved from lying (supine or prone) to upright (standing or sitting) positions. These changes were more pronounced for constant-current than for constant-voltage pulse generators and more often led to stimulation-evoked discomfort. These observations are consistent with postural changes in spinal cord position measured in imaging studies, and with computer model predictions of neural recruitment for these different spinal cord positions. These observations have implications for the design, implantation, and clinical application of spinal cord stimulators, not only for conventional paresthesia-based SCS but also for paresthesia-free SCS.
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Affiliation(s)
- Richard B North
- Neuromodulation Foundation, Inc, Baltimore, MD; Departments of Neurosurgery, Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD.
| | - Jung H Sung
- Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, MD
| | - Liam A Matthews
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI; Biointerfaces Institute, University of Michigan, Ann Arbor, MI
| | - Hans J Zander
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI; Biointerfaces Institute, University of Michigan, Ann Arbor, MI
| | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI; Biointerfaces Institute, University of Michigan, Ann Arbor, MI; Department of Anesthesiology, University of Michigan, Ann Arbor, MI
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Su PYP, Arle J, Poree L. Closing the loop and raising the bar: Automated control systems in neuromodulation. Pain Pract 2024; 24:177-185. [PMID: 37638532 DOI: 10.1111/papr.13290] [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: 04/20/2023] [Accepted: 08/04/2023] [Indexed: 08/29/2023]
Abstract
INTRODUCTION Neuromodulation has emerged as a promising therapy for the management of chronic pain, movement disorders, and other neurological conditions. Spinal cord stimulation (SCS) is a widely used form of neuromodulation that involves the delivery of electrical impulses to the spinal cord to modulate the transmission of pain signals to the brain. In recent years, there has been increasing interest in the use of automation systems to improve the efficacy and safety of SCS. This narrative review summarizes the status of Food and Drug Administration-approved autonomous neuromodulation devices including closed loop, feedforward, and feedback systems. The review discusses the advantages and disadvantages of each system and focuses specifically on the use of these systems for SCS. It is important for clinicians to understand the expanding role of automation in neuromodulation in order to select appropriate therapies founded on automation systems to the specific needs of the patient and the underlying condition. CONCLUSION The review also provides insights into the current state of the art in neuromodulation automation systems and discusses potential future directions for research in this field.
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Affiliation(s)
- Po-Yi Paul Su
- Department of Anesthesia, University of California San Francisco, San Francisco, California, USA
| | | | - Lawrence Poree
- Department of Anesthesia, University of California San Francisco, San Francisco, California, USA
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Single PS, Scott JB, Mugan D. Measures of Dosage for Spinal-Cord Electrical Stimulation: Review and Proposal. IEEE Trans Neural Syst Rehabil Eng 2023; 31:4653-4660. [PMID: 37983153 DOI: 10.1109/tnsre.2023.3335100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
This manuscript proposes an electrical definition of therapeutic dose for spinal-cord systems used for the treatment of chronic pain, analogous to the pharmacological definition. Dose-response relationships are fundamental to pharmacology, radio-therapy, and other treatments, but have never been properly established for neuromodulation. This manuscript offers a robust measure of dose, pre-requisite to establishing a reliable and repeatable dose-response relationship. The new definition, enabled by the system transresistance obtained from measurement of evoked action potentials, recognizes the mechanism of action of spinal cord stimulation (SCS), and should improve acceptance of the therapy as compared to pharmacological treatments which are currently used more frequently for the treatment of chronic pain. The new definition suggests methods for personalization and standardization of the dose in SCS, and is potentially generalizable to all neuromodulation therapies in which nervous tissue is excited including sacral nerve stimulation (SNS), vagal nerve stimulation (VNS) and deep-brain stimulation (DBS). Formulas are provided, and applied using patient data. Powerful conclusions are drawn from application of the new measure.
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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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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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Verma N, Knudsen B, Gholston A, Skubal A, Blanz S, Settell M, Frank J, Trevathan J, Ludwig K. Microneurography as a minimally invasive method to assess target engagement during neuromodulation. J Neural Eng 2023; 20:10.1088/1741-2552/acc35c. [PMID: 36898148 PMCID: PMC10587909 DOI: 10.1088/1741-2552/acc35c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 03/10/2023] [Indexed: 03/12/2023]
Abstract
Objective.Peripheral neural signals recorded during neuromodulation therapies provide insights into local neural target engagement and serve as a sensitive biomarker of physiological effect. Although these applications make peripheral recordings important for furthering neuromodulation therapies, the invasive nature of conventional nerve cuffs and longitudinal intrafascicular electrodes (LIFEs) limit their clinical utility. Furthermore, cuff electrodes typically record clear asynchronous neural activity in small animal models but not in large animal models. Microneurography, a minimally invasive technique, is already used routinely in humans to record asynchronous neural activity in the periphery. However, the relative performance of microneurography microelectrodes compared to cuff and LIFE electrodes in measuring neural signals relevant to neuromodulation therapies is not well understood.Approach.To address this gap, we recorded cervical vagus nerve electrically evoked compound action potentials (ECAPs) and spontaneous activity in a human-scaled large animal model-the pig. Additionally, we recorded sensory evoked activity and both invasively and non-invasively evoked CAPs from the great auricular nerve. In aggregate, this study assesses the potential of microneurography electrodes to measure neural activity during neuromodulation therapies with statistically powered and pre-registered outcomes (https://osf.io/y9k6j).Main results.The cuff recorded the largest ECAP signal (p< 0.01) and had the lowest noise floor amongst the evaluated electrodes. Despite the lower signal to noise ratio, microneurography electrodes were able to detect the threshold for neural activation with similar sensitivity to cuff and LIFE electrodes once a dose-response curve was constructed. Furthermore, the microneurography electrodes recorded distinct sensory evoked neural activity.Significance.The results show that microneurography electrodes can measure neural signals relevant to neuromodulation therapies. Microneurography could further neuromodulation therapies by providing a real-time biomarker to guide electrode placement and stimulation parameter selection to optimize local neural fiber engagement and study mechanisms of action.
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Affiliation(s)
- Nishant Verma
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Bruce Knudsen
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Aaron Gholston
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Aaron Skubal
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Stephan Blanz
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Megan Settell
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Jennifer Frank
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
| | - James Trevathan
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Kip Ludwig
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
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Cedeño DL, Vallejo R, Kelley CA, Platt DC, Litvak LM, Straka M, Dinsmoor DA. Spinal Evoked Compound Action Potentials in Rats With Clinically Relevant Stimulation Modalities. Neuromodulation 2023; 26:68-77. [PMID: 35961888 DOI: 10.1016/j.neurom.2022.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 06/07/2022] [Accepted: 06/29/2022] [Indexed: 01/11/2023]
Abstract
OBJECTIVES Rats are commonly used for translational pain and spinal cord stimulation (SCS) research. Although many SCS parameters are configured identically between rats and humans, stimulation amplitudes in rats are often programmed relative to visual motor threshold (vMT). Alternatively, amplitudes may be programmed relative to evoked compound action potential (ECAP) thresholds (ECAPTs), a sensed measure of neural activation. The objective of this study was to characterize ECAPTs, evoked compound muscle action potential thresholds (ECMAPTs), and vMTs with clinically relevant SCS modalities. MATERIALS AND METHODS We implanted ten anesthetized rats with two quadripolar epidural SCS leads: one for stimulating in the lumbar spine, and another for sensing ECAPs in the thoracic spine. We then delivered two SCS paradigms to the rats. The first used 50-Hz SCS with 50-, 100-, 150-, and 200-μs pulse widths (PWs), whereas the second used a 50-Hz, 150-μs PW low-rate program (LRP) multiplexed to a 1200-Hz, 50-μs PW high-rate program (HRP). We increased SCS amplitudes up to the vMT in the first paradigm, and in the second, we increased HRP amplitudes up to the HRP ECAPT with a fixed amplitude (70% of the vMT) LRP. For each test case, we captured ECAPTs, ECMAPTs, and vMTs from each rat. RESULTS vMTs were 3.0 ± 0.7 times greater than ECAPTs, with vMTs marginally (3.0 ± 3.6%) greater than ECMAPTs (mean ± SD) across all PWs with the first paradigm. With the second paradigm, we noted a negligible increase (3.6 ± 6.2%) on the LRP ECAP as HRP amplitudes were increased. CONCLUSIONS Our results demonstrate reasonable levels of neural activation in anesthetized rats with SCS amplitudes appropriately programmed relative to vMT or ECMAPT when using clinically relevant SCS modalities. Furthermore, we demonstrate the feasibility of ECAP recording in rats with multiplexed HRP SCS.
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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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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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