The test-retest reliability of large and small fiber nerve excitability testing with threshold tracking.
(2023) Clinical neurophysiology practice — Vol. 8, p. 71-78 (2023)
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- (en) 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.
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Pia, H., Nochi, Z., Kristensen, A. G., Pelz, B., Goetz, M., Hoeink, J.-N., Blockeel, A. J., Mouraux, A., Truini, A., Finnerup, N. B., Phillips, K. G., Treede, R.-D., & Tankisi, H. (2023). The test-retest reliability of large and small fiber nerve excitability testing with threshold tracking. Clinical neurophysiology practice, 8, 71-78. https://doi.org/10.1016/j.cnp.2023.03.003 (Original work published 2023)