Neuromodulation of lower limb motor responses with transcutaneous lumbar spinal cord direct current stimulation

Publication date: September 2018

Source: Clinical Neurophysiology, Volume 129, Issue 9

Author(s): Mariana Pereira, Sofia Rita Fernandes, Pedro C. Miranda, Mamede de Carvalho

Abstract

Objective

Trans-spinal direct current stimulation (tsDCS) is a promising technique to modulate spinal circuits. Combining clinical with modelling studies can improve effectiveness of tsDCS protocols. The aim of this study is to measure the effects of lumbar tsDCS on motor spinal responses and observe if these are consistent with the electric field (E-field) predicted from a computational model.

Methods

The exploratory study design was double-blind crossover and randomized. tsDCS was delivered for 15 min (anodal, cathodal, sham) at L2 vertebra level (2.5 mA, 90 C/cm²) in 14 healthy subjects. F-wave, H-reflex, cortical silent period, motor evoked potential and sympathetic skin response were analyzed. Statistical methods were applied with Bonferroni correction for multiple comparisons, a p < 0.05 was set as significant. A human volume conductor model was obtained from available databases. E-field distributions in the spinal grey matter (GM) and white matter (WM) were calculated.

Results

No tsDCS effects were observed. E-field magnitude predicted in the lumbosacral spinal GM and WM was <0.15 V/m, insufficient to ensure neuromodulation, which is consistent with the absence of effects.

Conclusion

The tsDCS protocol applied did not change motor response to delivered stimulus, thus we observed no effect on motor spinal circuits.

Significance

Future tsDCS protocols should be supported by computational models.

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