Advances in non-invasive monitoring of drug delivery for neurodegenerative disorders

INTRODUCTION: Effective therapies for neurodegenerative disorders remain limited by the blood-brain barrier. However, improving delivery across this barrier is only one part of the challenge. Investigators must also determine whether a therapy reaches the intended brain region, engages its target, and produces a meaningful biological response. AREAS COVERED: This narrative review examines emerging approaches for noninvasive monitoring of central nervous system drug delivery. The literature search included PubMed and Web of Science for studies published from 2005 until 2026. Imaging methods such as magnetic resonance imaging, positron emission tomography, and focused ultrasound provide spatial information about blood-brain barrier permeability, regional distribution, and target engagement. Theranostic nanoplatforms and nanocarrier tracking strategies make delivery agents visible, while blood-based biomarkers, biosensors, and wearable technologies offer complementary measures of pharmacodynamic response and functional change. The literature search prioritized peer-reviewed original studies, clinical trials, and recent translational work relevant to delivery verification, biological response, and treatment monitoring. EXPERT OPINION: Noninvasive monitoring is shifting CNS drug delivery from a question of blood-brain barrier crossing to a broader framework for evaluating delivery success. Future trials should validate whether multimodal monitoring can guide dosing, patient selection, safety surveillance, and continuation of treatment.