Dissociable effects of β-tACS on spectral power and network organization for proximal versus distal upper-limb recovery in subacute stroke: double-blind, randomized, sham-controlled trial with high-density EEG.

Single centre and 56 patients analysed, 28 per group, so the study is small and comes from one hospital; the results may not transfer to other settings or populations. Only 10 stimulation sessions over two weeks with a one-month follow-up. The authors say this dose may not have been enough to produce hand gains, so the negative hand result means 'not shown at this dose', not 'stimulation cannot help the hand'. The sample size was calculated for the shoulder and elbow subscore at one month rather than for the total upper-limb score that the paper names as its primary objective. Stimulation was centred on the motor cortex rather than focal. With sponge electrodes and a return electrode on the shoulder, the current was spread out, so the study cannot show which brain region produced the effect. EEG was recorded at rest, not during movement, so the observed brain changes cannot be assumed to reflect how patients actually control the arm in daily life. Lesion location was recorded only as cortical, subcortical or brainstem, so specific lesion sites and corticospinal tract damage cannot be ruled out as explanations, particularly for the weak hand results. The finding that people without recordable motor evoked potentials improved more comes from a subgroup analysis in a modest sample; it is a hypothesis, not a rule for selecting patients. Responder results depend on minimal-important-difference cut-offs that vary between populations, which the authors themselves describe as supportive rather than definitive.

Funded by the Gusu District Health Talent Training Project and the Science and Technology Program of Suzhou, both public regional funding bodies; no commercial sponsor or device manufacturer is named. The text supplied contains no conflicts-of-interest declaration beyond the funding statement.

Do not read this as evidence that stimulation helps the hand. The wrist and hand difference between groups did not reach statistical significance at either time point (p = 0.089 after treatment, p = 0.170 at one month), and the authors themselves say the benefit was clearer for proximal recovery. Also, this is a single trial of 56 people at one centre, so it does not yet make stimulation part of routine therapy.