DOCK3 and essential thrombocythemia: ET showed weaker clinical associations though MoCA correlated positively with right-hemisphere ALPS (ρ=0.462, p=0.018).  CONCLUSION: The findings indicate perivascular diffusivity is reduced in both tremor-dominant PD and ET, supporting a role for glymphatic dysfunction in their pathophysiology, though larger, prospective studies are needed to validate this observation.