Chronic manganism: A long-term follow-up study with a new dopamine terminal biomarker of ¹⁸F-FP-(+)-DTBZ (¹⁸F-AV-133) brain PET scan

Recent experimental studies revealed that dopamine neuron dysfunction in chronic manganism may be due to a reduced capacity of dopamine release in the striatum. The findings imposed further difficulty in the differential diagnosis between manganism and IPD. We conducted a long-term clinical follow-up study of 4 manganism patients, applying a new tracer ¹⁸F-9-fluoropropyl-(+)-dihydrotetrabenazine (¹⁸F-AV-133) with positron emission tomography (PET). Twenty age-matched subjects including 4 manganism patients, 8 idiopathic Parkinson's disease (IPD) patients, and 8 healthy controls were enrolled for comparison. Volumes of interest of the bilateral putamen, caudate nuclei and occipital cortex as the reference region were delineated from individual magnetic resonance images. The clinical features of the manganism patients still progressed, with increased scores on the Unified Parkinson Disease Rating Scale. The ¹⁸F-AV-133 uptake in the IPD patients decreased at the bilateral striatum, compared with the healthy controls. In the manganism patients, there was no decreased uptake of radioactivity involving the bilateral striatum, except Patient 4, who had a stroke with decreased uptake in the right posterior putamen. The ¹⁸F-AV-133 PET finding reveals that nigrostriatum neurons are not degenerated in chronic manganism and can provide a useful neuroimage biomarker in the differential diagnosis.