Cortical metabolic 18F-FDG PET assessment and striatal dopamine transporter SPECT imaging in suspected early neurodegenerative disorders with uncertain movement and cognitive symptoms

Aim/Introduction: Neurodegenerative diseases are generally classifed basing on cognitive (CS) or motor (MS) symptoms; however, in some cases both symptom simultaneous presence especially in disease early phase makes diferential diagnosis uncertain and difcult. We evaluated whether 18F-FDG PET cortical metabolism study combined with striatal dopamine-transporter 123I-Iofupane SPECT might support clinical diagnosis in patients with these two disorders uncertain symptoms. Materials and Methods: We retrospectively studied 45 consecutive patients who referred recent appearance of both CS and MS symptoms, but with uncertain clinical neurological exam, doubtful neuropsychological tests and aspecifc magnetic resonance imaging. Within three weeks, all patients underwent both PET and SPECT, according to International Guidelines. PET and SPECT images were evaluated both qualitatively (QL) and quantitatively (QN), the latter using two dedicated software that consider age-matched normal controls and provide z score (-2.0) parameter and binding potential (BP) cut of value (3.3) for PET and SPECT, respectively. A clinical follow up of 12- 18 months confrmed diagnosis. Results: At PET QL analysis, 34/45 cases had diferent areas of cortical hypometabolism, while 11/45 showed normal metabolism; at PET QN analysis, 38/45 cases had pathological z score in diferent cortical areas and the remaining 7/45 cases confrmed normal z score values. At SPECT QL analysis, 19/45 patients showed mild to severe striatal 123I-Iofupane uptake reduction, while 26/45 cases had normal uptake. At SPECT QN analysis, 23/45 cases (fve of these normal at QL) evidenced low BP values while the other 22/45 cases had normal values. Associating QL and QN analyses of the two procedures, in 16/45 patients both PET and SPECT were pathological as from dopaminergic and cognitive associated diseases; 7/45 cases with normal PET and pathological SPECT were considered as MS without CS. The 15/45 cases with pathological PET and normal SPECT were classifed as CS without MS. In the remaining 7/45 cases with normal PET and SPECT both MS and CS were excluded. Conclusion: 18F-FDG PET and 123I-Iofupane SPECT combined use proved useful to discriminate CS and MS disorders in early stage also achieving to identify and characterize the patients with the two neurodegenerativeassociated disorders (35.5%). This performance permitted a better appropriate patient management and a suitable therapy. The two procedures could exclude both diseases in some cases avoiding unnecessary treatments. PET and SPECT QN analyses gave better results than traditional QL analysis suggesting its wider use even more when QL is inconclusive for the diagnosis.