“…• Structural MRI MRI signs: putaminal rim sign, hot cross bun sign, middle cerebellar peduncles (MCP) sign Striatonigral and olivopontocerebellar atrophy is observed in MSA vs. NC ↓ in putamen, MCP, cerebellum, and pons in MSA-P vs. PD Supratentorial atrophy (putamen) in MSA-P, whereas infratentorial atrophy in MSA-C may be more predominant (11,28,71,99,102,103,(106)(107)(108)(109)(110) (Continued) • Proton MRS ↓ NAA/Cr ratio in putamen in MSA-P, and in pontine base in both MSA-P and MSA-C vs. NC ↓ NAA/Cr ratio in putamen and pontine base may discriminate MSA-P from PD (120) • PET and SPECT b Glucose metabolism: MSA-related spatial covariance pattern may involve metabolic ↓ in putamen and cerebellum (273,279) Dopaminergic system: b ↓ striatal presynaptic DAT binding and ↓ dopamine D2 receptor binding vs. NC (225,241,242) Neuroinflammation: ↑ microglial activity in dorsolateral prefrontal cortex, putamen, pallidum, pons, and SN vs. NC (332) • Transcranial S b ↑ LN echogenicity along with normal or ↑ SN echogenicity may be seen (188,197) AD clinical outcomes (320). Some of the developmental challenges [see reference (321)], although similar to those of tau PET radiotracers, include the intracellular nature of most α-synuclein aggregates requiring ideal lipophilicity and molecular size, multiple α-synuclein strains that may interact differently with some tracers, colocalization of α-synuclein with other protein aggregates, relatively less abundance of α-synuclein over amyloid and tau aggregates requiring higher tracer selectivity, as well as the potential for off-target binding which may necessitate further validation.…”