Non-invasive brain stimulation in frontotemporal dementia: syndrome-specific signals and priorities for future trials.

Frontotemporal dementia is the second most common cause of young-onset dementia after Alzheimer's disease and lacks disease-modifying treatment. This narrative review summarizes human studies of non-invasive brain stimulation, including repetitive transcranial magnetic stimulation and theta-burst stimulation, transcranial electrical stimulation, and transcranial photobiomodulation, in frontotemporal dementia and primary progressive aphasia. We review stimulation targets, protocols, outcomes, and safety, and organize the evidence by clinical subtype and modality. Current data remain preliminary, but recurrent signals support prefrontal and cerebellar repetitive transcranial magnetic stimulation/theta-burst stimulation and prefrontal or temporoparietal transcranial direct current stimulation, particularly in primary progressive aphasia. By contrast, controlled evidence in behavioral-variant frontotemporal dementia is limited and heterogeneous. Future trials should be sham-controlled, multicenter, and syndrome-stratified; combine stimulation with symptom-relevant cognitive or language therapy; and incorporate biomarker-informed targeting, target-engagement measures, and longer follow-up to determine durability and clinical relevance.