Abstract
Objective
Standard nerve excitability testing (NET) predominantly assesses Aα- and Aβ-fiber function, but a method examining small afferents would be of great interest in pain studies. Here, we examined the properties of a novel perception threshold tracking (PTT) method that preferentially activates Aδ-fibers using weak currents delivered by a novel multipin electrode and compared its reliability with NET.
Methods
Eighteen healthy subjects (mean age:34.06 ± 2.0) were examined three times with motor and sensory NET and PTT in morning and afternoon sessions on the same day (intra-day reliability) and after a week (inter-day reliability). NET was performed on the median nerve, while PTT stimuli were delivered through a multipin electrode located on the forearm. During PTT, subjects indicated stimulus perception via a button press and the intensity of the current was automatically increased or decreased accordingly by Qtrac software. This allowed changes in the perception threshold to be tracked during strength-duration time constant (SDTC) and threshold electrotonus protocols.
Results
The coefficient of variation (CoV) and interclass coefficient of variation (ICC) showed good–excellent reliability for most NET parameters. PTT showed poor reliability for both SDTC and threshold electrotonus parameters. There was a significant correlation between large (sensory NET) and small (PTT) fiber SDTC when all sessions were pooled (r = 0.29, p = 0.03).
Conclusions
Threshold tracking technique can be applied directly to small fibers via a psychophysical readout, but with the current technique, the reliability is poor.
Significance
Further studies are needed to examine whether Aβ-fiber SDTC may be a surrogate biomarker for peripheral nociceptive signalling.
Standard nerve excitability testing (NET) predominantly assesses Aα- and Aβ-fiber function, but a method examining small afferents would be of great interest in pain studies. Here, we examined the properties of a novel perception threshold tracking (PTT) method that preferentially activates Aδ-fibers using weak currents delivered by a novel multipin electrode and compared its reliability with NET.
Methods
Eighteen healthy subjects (mean age:34.06 ± 2.0) were examined three times with motor and sensory NET and PTT in morning and afternoon sessions on the same day (intra-day reliability) and after a week (inter-day reliability). NET was performed on the median nerve, while PTT stimuli were delivered through a multipin electrode located on the forearm. During PTT, subjects indicated stimulus perception via a button press and the intensity of the current was automatically increased or decreased accordingly by Qtrac software. This allowed changes in the perception threshold to be tracked during strength-duration time constant (SDTC) and threshold electrotonus protocols.
Results
The coefficient of variation (CoV) and interclass coefficient of variation (ICC) showed good–excellent reliability for most NET parameters. PTT showed poor reliability for both SDTC and threshold electrotonus parameters. There was a significant correlation between large (sensory NET) and small (PTT) fiber SDTC when all sessions were pooled (r = 0.29, p = 0.03).
Conclusions
Threshold tracking technique can be applied directly to small fibers via a psychophysical readout, but with the current technique, the reliability is poor.
Significance
Further studies are needed to examine whether Aβ-fiber SDTC may be a surrogate biomarker for peripheral nociceptive signalling.
| Original language | English |
|---|---|
| Pages (from-to) | 71-78 |
| Number of pages | 8 |
| Journal | Clinical Neurophysiology Practice |
| Volume | 8 |
| Early online date | 30 Mar 2023 |
| DOIs | |
| Publication status | E-pub ahead of print - 30 Mar 2023 |
Bibliographical note
Funding Information:This project has received funding from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No [777500]. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme and EFPIA ( https://www.imi.europa.eu ; https://www.imi-paincare.eu ). The statements and opinions presented here reflect the author's view and neither IMI nor the European Union, EFPIA, or any Associated Partners are responsible for any use that may be made of the information contained therein. This study is also supported by the Lundbeck Foundation (Grant R359-2020-2620).
Publisher Copyright:
© 2023 International Federation of Clinical Neurophysiology