Quantitative analysis of striatal dopamine D2 receptors with I-123-iodolisuride SPECT in degenerative extrapyramidal diseases

I-123-Iodolisuride has high specific affinity for binding on dopamine D2 re ceptors in the striatum and has been used in a few single photon emission c omputed tomography (SPECT) studies of extrapyramidal disorders. The diagnos is of Parkinson's disease (PD) is very difficult in the first 5 years of ev olution, with 15-25% false positive diagnoses. The aim of this study was th erefore to determine the value of iodolisuride SPECT in discriminating Park inson's from the most frequent Parkinson-plus syndromes (PPS). Seventeen pa tients with an extrapyramidal syndrome had a SPECT examination 1 h after in jection of 180-185 MBq of I-123-iodolisuride. They were followed under dopa minergic treatment for at least 2 years. After 2 years, they were separated in two groups according to specific clinical criteria and sensitivity to d opaminergic treatment: nine patients had PD (age = 59.8+/-8.8 years; Hoehn and Yahr = 1.8+/-0.7; evolution = 4.3+/-3 years) and eight had PPS (age = 7 1.6+/-7.3 years; Hoehn and Yahr = 2.9+/-2.0; evolution = 4.1+/-1.5 years). The binding potential of iodolisuride in the striatum was assessed by consi dering the striatum (S)/occipital lobe (O) ratio at the pseudo-equilibrium 1 h after injection. The S/O ratio was statistically different between PD a nd PPS (1.97+/-0.3 vs 1.65+/-0.2 (P < 0.02)). Iodolisuride SPECT could diff erentiate both groups with a sensitivity of 88.8% and a specificity of 75%. Iodolisuride is a good specific D2 receptor ligand for SPECT and complemen ts specific clinical criteria for the diagnosis of Parkinson's disease and differentiation between different extrapyramidal disorders. ((C) 2001 Lippi ncott Williams & Wilkins).