Remote photobiomodulation: A systemic approach to neuroprotection

Photobiomodulation (PBM) therapy is rapidly gaining traction in clinical settings, with an expanding body of clinical trials investigating its efficacy as a non-invasive, non-pharmacological intervention to enhance tissue resilience and mitigate disease pathology. Among the most promising developments is the application of PBM in treating neurological conditions, offering new hope to millions affected by these intractable diseases. The prevailing approach in this field is transcranial PBM, where light is administered directly to the head under the assumption that photons can penetrate the scalp and skull to stimulate neural cells relevant to the targeted condition. Encouragingly, this approach has yielded positive outcomes in many studies, reinforcing the assumption and shaping subsequent research. However, in the enthusiasm to pioneer these potentially transformative therapies, a critical aspect is often overlooked: PBM can also exert indirect, systemic effects. Delivering therapeutic doses of light to one part of the body can produce pronounced benefits in distal tissues - a phenomenon supported by numerous animal experiments and emerging human data. Drawing a parallel to remote ischemic conditioning - where brief, controlled ischemia in a limb can induce resilience in vital organs like the heart and brain - we introduced the term "remote photobiomodulation" to describe this modality. This Chapter explores the concept of remote photobiomodulation: its origins, proposed mechanisms, and its relationship to transcranial PBM. By examining current evidence and theoretical frameworks, we aim to demonstrate why this underappreciated approach warrants deeper investigation and how it could broaden the therapeutic landscape for neurological disorders.