White Matter Integrity Predicts Electrical Stimulation (tDCS) and Language Therapy Effects in Primary Progressive Aphasia.
Yi Zhao, Bronte Ficek, Kimberly Webster and 5 others
PMID 33317422WHAT IT FOUND
Adding left frontal tDCS to written naming and spelling therapy improved trained words more than therapy alone, and only tDCS improved untrained words.
Baseline white-matter tracts were associated with gains in both groups.
Key findings
01tDCS paired with written naming and spelling therapy improved trained words more than sham therapy, and the tDCS advantage became greater over time.
02Only the tDCS group maintained significant improvement on untrained words, and it scored significantly higher than sham at two months.
03Baseline white-matter integrity measures were associated with letter-accuracy gains in both the tDCS and therapy-only groups.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample was small: 39 people with PPA, and one participant dropped out. The white-matter predictor analysis fitted 48 models and used stepwise selection, so some associations may be chance findings or overfitting. The imaging method used region-of-interest analysis rather than tractography and could not reliably distinguish the uncinate fasciculus from the extreme capsule. FA and MD are sensitive but non-specific white-matter measures, and their cellular basis is not definitive. The study focused only on the language network, so attention, learning, and other functions that could affect therapy were not assessed. The supplied text does not give the actual letter-accuracy scores, so the size of the clinical benefit cannot be judged. The trial is described as crossover, but the supplied text does not fully explain how participants received each condition or how order effects were handled.
Declared interests
The supplied text reports funding from a Science of Learning Institute award at Johns Hopkins University and NIH/NIDCD R01 DC014475, but no conflict-of-interest declaration.
The easy way to misread this
Do not conclude that tDCS alone caused the gains or that white-matter scans can guide treatment now. The effect was tDCS delivered together with written naming and spelling therapy, and the trial was small with exploratory white-matter models.