Predicting upper extremity motor improvement following therapy using EEG-based connectivity in chronic stroke.

Only 12 people finished the study, and the authors call the small sample size the primary limitation. A link found in a dozen people can look quite different in a larger group, and the authors themselves ask for a larger study to confirm it. The participants all had mild-to-moderate arm weakness, could follow three-step instructions, and could perform a grip task. Nothing here applies to people with severe arm weakness or to people who cannot follow instructions. Two of the twelve had no MRI and were modelled on an average brain template instead of their own scan, so the lesion-specific part of the method was weaker for them. Therapy lasted only two weeks, which the authors say was likely too short to produce large motor gains. Improvement was measured on average six days after the last session, so the study says nothing about whether any gains lasted. This is a secondary analysis of a pilot trial. The original trial was not designed or powered to answer the question this analysis asks, and the original trial reported that the vibration group improved more, which this analysis of 12 people cannot confirm or refute.

One author (N.J. Seo) is listed as an inventor on a patent covering the subthreshold vibratory stimulation used in this study. The other authors report no conflicts of interest.

Do not read this as a test you can use to predict an individual patient's arm recovery, and do not read it as proof that adding wrist vibration to task practice helps. The link was found in 12 people in a secondary analysis of a pilot trial, the authors themselves name the small sample size as the primary limitation, and the analysis found no significant difference in improvement between the vibration and no-vibration groups in this sample.