contrast, Parkinson's tremors are rest tremors, and usually start unilaterally. Imaging SPECT with iodine-123 labeled 2-²-carboxymethoxy-3-²-(4-iodophenyl)tropane ([123I]²-CIT) or IBZM and PET with 18 F-fluorodopa are imaging modalities used to assess the dopamine transporter density and nigrostriatal pathway integrity in the central nervous system. Neither have any place yet in the routine