... when in doubt, a good group of neurologists, as found at "centers of excellence" will book you for one of two tests involving radiochemistry in an attempt to visualize the dopamine transporter itself, that is the substantia nigra and pars compacta where dopamine itself is produced and stored for transport as a neurotransmitter. The first is called a Spect scan, which uses an iodine 123 radiolabelled compound that binds tightly to dopamine receptors. It makes a picture of dopamine activity in the brain around where the receptors are most dense, if the picture shows small areas of low "ligand binding", it is a surefire way of proving that your troubles are due to lack of dopamine transmission. THe next is a F-19 dopa PET scan, which is a different way of doing the same thing except a different "radioactive ligand" and a different machine is used to see a lack of dopaminergic transmission.