Nigrostriatal imaging in patients with clinically uncertain Parkinsonian syndromes: a head-to-head comparison between SPECT, PET, and MRI.

purposeNeurodegenerative parkinsonism is characterized by degeneration of the dopaminergic nigrostriatal pathways and a reduction in nigral neuromelanin. Dopamine transporter (DAT) imaging assesses presynaptic striatal dopaminergic function and is typically performed with [

methodsIn this study, we conducted a head-to-head comparison of [¹²³I]FP-CIT SPECT, [¹⁸F]FE-PE2I PET, and nigral MRI in 35 patients referred for diagnostic DAT imaging. Nigral MRI was performed with neuromelanin-sensitive gradient echo magnetization-transfer contrast MRI and iron-sensitive STrategically Acquired Gradient Echo (STAGE) MRI. Patient satisfaction with SPECT and PET was recorded via questionnaires.

resultsEighteen patients were diagnosed with neurodegenerative parkinsonism with a median symptom duration of 29 months. DAT availability as measured with SPECT and PET showed complete concordance across cases, correlated strongly, and demonstrated equally excellent diagnostic performance. Patient questionnaire items were either not different between modalities or in favor of SPECT. Nigral neuromelanin content was reduced in patients with neurodegenerative parkinsonism and provided intermediate diagnostic accuracy, with indications of lower neuromelanin with disease duration. Midbrain iron content did not differ between groups and provided no diagnostic information.

conclusionOur findings indicate that in early-stage parkinsonism, DAT neuroimaging with SPECT and PET provides comparable and superior diagnostic value relative to nigral MRI.