More specifically, presynaptic dopamine transporter imaging is well suited to distinguish between parkinsonism-associated tremor and ET,64 and dystonic tremor, which can be a cause of scans without evidence of dopaminergic deficit in suspected patients with PD.65 However, although presynaptic dopamine transporter imaging is used to distinguish drug-induced parkinsonism from neurodegenerative forms of parkinsonism,66 it cannot reliably make a distinction between the different causes of a parkinsonism-associated tremor.67 The gene discussed is SLC6A3; the disease is essential thrombocythemia.