PMID- 38416179
OWN - NLM
STAT- MEDLINE
DCOM- 20240329
LR  - 20240330
IS  - 1432-1106 (Electronic)
IS  - 0014-4819 (Print)
IS  - 0014-4819 (Linking)
VI  - 242
IP  - 4
DP  - 2024 Apr
TI  - Distinguishing reflex from non-reflex responses elicited by transcutaneous spinal 
      stimulation targeting the lumbosacral cord in healthy individuals.
PG  - 959-970
LID - 10.1007/s00221-024-06790-2 [doi]
AB  - Transcutaneous spinal stimulation (TSS) studies rely on the depolarization of 
      afferent fibers to provide input to the spinal cord; however, this has not been 
      routinely ascertained. Thus, we aimed to characterize the types of responses 
      evoked by TSS and establish paired-pulse ratio cutoffs that distinguish posterior 
      root reflexes, evoked by stimulation of afferent nerve fibers, from motor 
      responses, evoked by stimulation of efferent nerve fibers. Twelve neurologically 
      intact participants (six women) underwent unipolar TSS (cathode over T11-12 
      spinal processes, anode paraumbilically) while resting supine. In six 
      participants, unipolar TSS was repeated 2-3 months later and also compared to a 
      bipolar TSS configuration (cathode 2.5 cm below T11-12, anode 5 cm above 
      cathode). EMG signals were recorded from 16 leg muscles. A paired-pulse paradigm 
      was applied at interstimulus intervals (ISIs) of 25, 50, 100, 200, and 400 ms. 
      Responses were categorized by three assessors into reflexes, motor responses, or 
      their combination (mixed responses) based on the visual presence/absence of 
      paired-pulse suppression across ISIs. The paired-pulse ratio that best 
      discriminated between response types was derived for each ISI. These cutoffs were 
      validated by repeating unipolar TSS 2-3 months later and with bipolar TSS. 
      Unipolar TSS evoked only reflexes (90%) and mixed responses (10%), which were 
      mainly recorded in the quadriceps muscles (25-42%). Paired-pulse ratios of 0.51 
      (25-ms ISI) and 0.47 (50-ms ISI) best distinguished reflexes from mixed responses 
      (100% sensitivity, > 99.2% specificity). These cutoffs performed well in the 
      repeated unipolar TSS session (100% sensitivity, > 89% specificity). Bipolar TSS 
      exclusively elicited reflexes which were all correctly classified. These results 
      can be utilized in future studies to ensure that the input to the spinal cord 
      originates from the depolarization of large afferents. This knowledge can be 
      applied to improve the design of future neurophysiological studies and increase 
      the fidelity of neuromodulation interventions.
CI  - (c) 2024. The Author(s).
FAU - Gordineer, Elizabeth A
AU  - Gordineer EA
AUID- ORCID: 0000-0003-3895-4849
AD  - School of Graduate Studies in the Health Sciences, Program in Neuroscience, 
      University of Mississippi Medical Center, Jackson, MS, USA.
AD  - Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation 
      Center, Jackson, MS, USA.
FAU - Stokic, Dobrivoje S
AU  - Stokic DS
AUID- ORCID: 0000-0002-1891-5730
AD  - Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation 
      Center, Jackson, MS, USA.
FAU - Krenn, Matthias J
AU  - Krenn MJ
AUID- ORCID: 0000-0002-3398-3627
AD  - Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation 
      Center, Jackson, MS, USA. mkrenn@umc.edu.
AD  - Department of Neurosurgery, University of Mississippi Medical Center, 2500 N 
      State St, Jackson, MS, 39216, USA. mkrenn@umc.edu.
LA  - eng
GR  - WFLUS-07/19: 199/Wings for Life/
PT  - Journal Article
DEP - 20240228
PL  - Germany
TA  - Exp Brain Res
JT  - Experimental brain research
JID - 0043312
SB  - IM
MH  - Humans
MH  - Female
MH  - *Spinal Cord/physiology
MH  - Reflex/physiology
MH  - Muscle, Skeletal/physiology
MH  - Leg/physiology
MH  - *Spinal Cord Stimulation/methods
MH  - Electric Stimulation/methods
PMC - PMC10973043
OTO - NOTNLM
OT  - Electrical stimulation
OT  - Evoked motor response
OT  - Neurophysiology
OT  - Post-activation depression
OT  - Spinal reflex
OT  - Transcutaneous spinal cord stimulation
COIS- No conflicts of interest, financial or otherwise, are declared by the authors.
EDAT- 2024/02/28 12:42
MHDA- 2024/03/29 06:46
PMCR- 2024/02/28
CRDT- 2024/02/28 11:05
PHST- 2023/12/02 00:00 [received]
PHST- 2024/01/21 00:00 [accepted]
PHST- 2024/03/29 06:46 [medline]
PHST- 2024/02/28 12:42 [pubmed]
PHST- 2024/02/28 11:05 [entrez]
PHST- 2024/02/28 00:00 [pmc-release]
AID - 10.1007/s00221-024-06790-2 [pii]
AID - 6790 [pii]
AID - 10.1007/s00221-024-06790-2 [doi]
PST - ppublish
SO  - Exp Brain Res. 2024 Apr;242(4):959-970. doi: 10.1007/s00221-024-06790-2. Epub 
      2024 Feb 28.