The sensitivity ¹²³I-FP-CIT SPECT in Lewy body disease: is dopamine transporter reduced also when overt parkinsonism is lacking?
Progetto State of the art: Lewy body disease (LBD) include Dementia with LB (DLB) and Parkinson disease (PD). Both need to be distinguished from other types of degenerative conditions because of important differences in patient management. The clinical diagnosis of DLB is easier when cognitive decline is associated with parkinsonism (p+) but it is an hard task in a subgroup of DLB cases lacking overt parkinsonism (p-).
Low dopamine transporter (DAT) uptake in the basal ganglia, as shown by Single Photon Emission Computed Tomography (SPECT) is a common result in PD patients as it depicts the loss of terminal axons as a consequence of degeneration of cells of the substantia nigra. In LBD, the Lewy bodies in the brain stem disrupt the projection fibres to the striata resulting in the loss of DAT, thus SPECT has been proposed as a useful diagnostic tool to support the diagnosis, but little is known about the sensitivity of this technique in p-DLB patients.
Objective and rationale The primary aim of this study is to evaluate the sensitivity of SPECT in detecting p-DLB cases as compared to the sensitivity of this technique in p+DLB.
Experimental plan: Forty outpatients with LBD (20 p+DLB and 20 p-DLB) will be consecutively recruited. The parkinsonism severity will be graded according to the Unified Parkinson Disease Rating Scale part III (UPDRS III). We will define an UPDRSIII score≤15 as p- and an UPDRS III score>15 as p+, respectively. All patients will undergo SPECT scans with ¹²³I-FP-CIT. A t-test will be performed to detect differences between groups.
Expected results and their relevance: we speculate that 123I-FP-CIT SPECT uptake will be reduced in all patients, in comparison to normal subjects, but we expect to find a gradient with p+DLB having intermediate values between p-DLB (higher) and PD (lower). If this hypothesis will be confirmed, 123I-FP-CIT SPECT can be extended to support the diagnosis of DLB also in patients lacking overt parkinsonism.