DIFFERENTIAL DISTRIBUTION OF STRIATAL [(123)L]BETA-CIT IN PARKINSONS-DISEASE AND PROGRESSIVE SUPRANUCLEAR PALSY, EVALUATED WITH SINGLE-PHOTON EMISSION TOMOGRAPHY

Functional imaging of the presynaptic dopaminergic activity using sing le-photon emission tomography (SPET) and iodine-123 labelled 2-beta-ca rboxymethoxy-3-beta-(4-iodophenyl)tropane ([I-123]beta-CIT) is importa nt for the assessment of disease severity and progression in patients with Parkinson's disease (PD). However, its capability to discriminate between different extrapyramidal disorders has not yet been assessed. The aim of this study was to evaluate the possibility of differentiat ing patients with PD and with progressive supranuclear palsy (PSP) by means of this method. The distribution of [I-123]beta-CIT in the basal ganglia was assessed in six normal subjects, 13 petients with PD and five patients with PSP in whom the disease was mild. SPET images were obtained 24+/-2 h after i.v. injection of the tracer using a brain-ded icated system (CERASPECT). MR and SPET images were co-registered in fo ur normal subjects and used to define a standard set of 16 circular re gions of interest (ROIs) on the slice showing the highest striatal act ivity. The basal ganglia ROIs corresponded to (1) the head of caudate, (2) a region of transition between the head of caudate and the anteri or putamen, (3) the anterior putamen and (4) the posterior putamen. A ratio of specific to non-displaceable striatal uptake was calculated n ormalising the activity of the basal ganglia ROIs to that of the occip ital cortex (V3 ''). ANOVA revealed a global reduction of V3 '' in all ROIs of PD and PSP patients compared with normal controls (P<0.0001). A Mann-Whitney U test showed that the difference between PD and PSP p atients was statistically significant for the caudate region only (Z v alue: 2.6; P<0.01). By subtracting V3 '' caudate values from those of the putamen, differentiation from PSP was possible in 10/13 PD patient s. In conclusion, analysis of [I-123]beta-CIT distribution in discrete striatal areas provides information on the relative caudate-putamen d amage, with different values being obtained in patients clinically dia gnosed as having either PD or PSP.