Diffusion Tensor Imaging in Progressive Supranuclear Palsy Versus Other Neurodegenerative Diseases: A Review

Progressive supranuclear palsy (PSP) is a complex neurodegenerative disorder that is frequently misdiagnosed, largely due to its overlapping clinical features with other neurodegenerative diseases, such as Parkinson's disease and multiple system atrophy. Accurate and early diagnosis remains a significant clinical challenge. In this context, diffusion tensor imaging (DTI), a specialized magnetic resonance imaging technique that measures the directional movement of water molecules in neural tissue, has emerged as a promising biomarker. This narrative review synthesizes current research on the utility of DTI in differentiating PSP from other neurodegenerative diseases. Multiple studies have reported significant alterations in DTI parameters—particularly fractional anisotropy and mean diffusivity—in key brain regions, including the superior cerebellar peduncle, thalamus, corticospinal tract, anterior parts of the corpus callosum, and prefrontal cortex. While classical radiological signs such as the hummingbird and Mickey Mouse signs remain highly specific for the classic Richardson syndrome (PSP-RS), superior to any results highlighted by studies of this review, in areas associated with other PSP subtypes, such as the frontal cortex, DTI has scored high rates of diagnostic accuracy, a point that could be more explored in future research efforts. Nonetheless, limitations including small sample sizes, heterogeneous study designs, and a predominant focus on the PSP-RS subtype restrict broader generalizability. Large-scale, multicenter studies are necessary to validate these findings across the diverse spectrum of PSP presentations and to establish DTI as a robust diagnostic tool.