BDNF provides many routes toward STN DBS-mediated disease modification.

The concept that subthalamic nucleus deep brain stimulation (STN DBS) may be disease modifying in Parkinson's disease (PD) is controversial. Several clinical trials that enrolled subjects with late-stage PD have come to disparate conclusions on this matter. In contrast, some clinical studies in early- to midstage subjects have suggested a disease-modifying effect. Dopaminergic innervation of the putamen is essentially absent in PD subjects within 4 years after diagnosis, indicating that any neuroprotective therapy, including STN DBS, will require intervention within the immediate postdiagnosis interval. Preclinical prevention and early intervention paradigms support a neuroprotective effect of STN DBS on the nigrostriatal system via increased brain-derived neurotrophic factor (BDNF). STN DBS-induced increases in BDNF provide a multitude of mechanisms capable of ameliorating dysfunction and degeneration in the parkinsonian brain. A biomarker for measuring brain-derived neurotrophic factor-trkB signaling, though, is not available for clinical research. If a prospective clinical trial were to examine whether STN DBS is disease modifying, we contend the strongest rationale is not dependent on a preclinical neuroprotective effect per se, but on the myriad potential mechanisms whereby STN DBS-elicited brain-derived neurotrophic factor-trkB signaling could provide disease modification. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.