Nuclear neuroimaging of dopamine transporter in Parkinsonism--role in routine clinical practice

Idiopathic Parkinson's disease (IPD) is a neurodegenerative condition characterized pathologically by the degeneration of dopaminergic neuron in the substantia nigra and production of intracytoplasmic inclusion bodies (Lewy body) in the retained neurons. Clinically, the disease is characterized by the presence of tremor, rigidity and bradykinesia. These clinical features also occur in other neurodegenerative diseases and by dopamine receptor antagonist drugs. Brain SPECT imaging of the dopamine transporter (DAT) with specific radioligands is a sensitive method for examining the integrity of the presynaptic dopaminergic system. However, with this main clinical application it is hard to diagnose patients with mild, incomplete, or uncertain Parkinsonism. The ligands belong to a group of compounds derived from cocaine that bind to the dopamine transporter and include â-CIT, IPT, TRODAT-1, FP-CIT tagged with either Iod-123 or Technetium-99m radioisotopes. DAT imaging is abnormal even in the earliest clinical presentation of IPD but a normal scan suggests an alternative diagnosis such as essential tremor, vascular Parkinsonism, drug-induced Parkinsonism, or psychogenic Parkinsonism.