L1CAM and Parkinson disease: Elevated α-synuclein within neuron-derived L1 cell adhesion molecule-positive extracellular vesicles (LEV) distinguishes prodromal PD patients from healthy controls with 85–91% sensitivity, discriminates between PD and tauopathies with 98% sensitivity, and accurately identifies early-PD patients with minimal motor impairment [98,99,100].