Cervical trans-spinal direct current stimulation: a modelling-experimental approach.
Sofia Rita Fernandes, Mariana Pereira, Ricardo Salvador and 2 others
PMID 31653265WHAT IT FOUND
Cervical direct current stimulation shortened hand motor response timing after cathodal stimulation in 10 healthy volunteers.
Sensory responses did not change. This is a lab finding, not evidence of clinical benefit.
Key findings
01A computational model predicted that the C3-T3 electrode placement produced the highest electric field magnitudes among the tested montages, reaching 0.40 and 0.50 V/m in C6-C7 spinal cord regions.
02In healthy volunteers, cathodal stimulation produced a shorter mean motor evoked potential latency in the hand muscle than sham, and this was the only motor measurement with a significant change.
03Upper limb sensory responses did not show a polarity-dependent neuromodulatory effect.
STILL TO COME
How it was doneWhat they found
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What it does not show
The experimental study included only 10 healthy volunteers, all young adults, so it cannot show effects in patients or older people. The outcomes were nerve and muscle measurements, not function, symptoms, or clinical improvement. The sensory pathway result was null; no polarity-dependent upper limb sensory neuromodulation could be ascertained. F-wave, H-reflex and conduction-time measurements were done in only 5 subjects, and the authors said these results were not conclusive. The computational model simplified spinal anatomy, including an artificially designed spinal grey matter and poor detail at nerve exits. The authors did not test ipsilateral cortical silent period or phrenic nerve responses, and did not record during stimulation or after offset. Multiple measurements were compared, and the significant sensory trend did not survive pairwise comparison.
Declared interests
Funding was provided by Fundação para a Ciência e Tecnologia.
The easy way to misread this
Do not conclude that cervical tsDCS improves upper limb function or can be used clinically. The study tested 10 healthy volunteers and measured nerve and muscle responses, not patient function, and the sensory outcome was null. The motor change was only a shorter hand muscle response timing after cathodal stimulation.