Optimizing transcutaneous spinal stimulation: excitability of evoked spinal reflexes is dependent on electrode montage.
Kelly Lynn Thatcher, Karen Emily Nielsen, Evan Blake Sandler and 3 others
PMID 39762915WHAT IT FOUND
For transcutaneous spinal stimulation, placing anodes over the umbilicus or iliac crests activates spinal circuits at lower intensities than midline placements.
This may improve tolerability and reduce skin risk, though these montages did not produce larger reflex responses at matched intensities.
Key findings
01Montages with anodes over the umbilicus or iliac crests required significantly lower stimulation intensities to elicit soleus reflexes compared to midline or paraspinal anode placements.
02These same montages produced a larger total area of spinal circuit activation across the recruitment curve, specifically in the nondominant leg.
03There were no significant differences in how tolerable participants found the six different electrode arrangements.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was conducted on healthy adults with intact neurological systems, so the findings may not fully generalize to people with spinal cord injury or other neurologic conditions. Stimulation was capped at 100 mA to ensure comfort, meaning results do not apply to individuals whose reflex thresholds are higher than this limit. Only the soleus muscle was assessed; other target muscles may respond differently to these montages. Tolerability was rated after intermittent paired pulses, which may not reflect the experience of continuous stimulation used during actual rehabilitation interventions.
Declared interests
Funded by the National Institutes of Health and the Hulse SCI Research Fund. The funders played no role in the design, conduct, or reporting of the study.
The easy way to misread this
Do not assume that lower thresholds mean stronger treatment effects. While DV-U and DV-I montages activated circuits at lower intensities, they did not produce larger reflex responses at matched intensities compared to other montages, and the study did not test functional walking or spasticity outcomes.