Management impact of imaging brain vesicular monoamine transporter type-2 (VMAT2) in clinically uncertain parkinsonian syndrome (CUPS) with ¹⁸F-AV133 and PET

Objectives: Idiopathic Parkinson’s disease (iPD) is a common neurodegenerative disorder where misdiagnosis occurs in up to 30% of patients after initial assessment and in 10-15% even after long-term follow-up. Vesicular monoamine transporter type II (VMAT2) imaging with PET allows assessment of the integrity of the presynaptic dopaminergic pathway. We investigated the management impact of VMAT2 imaging in patients with Clinically Uncertain Parkinsonian Syndromes (CUPS).

Methods: Forty-seven patients with CUPS (56±14.9 years, range 26-80) were referred from movement disorder specialists. All participants underwent a 20-minute PET acquisition two hours post injection of 250 MBq of ¹⁸F-AV-133, and the resulting images were quantitatively assessed. Clinical impact was recorded as high, moderate or low based on diagnosis and management questionnaires completed by the referring specialists pre and post release of the PET results. Management impact was high if there was a change in diagnostic category; moderate if there was a change in medication and low if there was no change.

Results: VMAT2 PET changed the diagnosis in 12 (26%) and medication in 25 (53%) participants. Management impact was high in 26%, moderate in 35% and low in 39% of the participants. High diagnostic confidence increased from 11% of patients to 80% after the release of the scan results

Conclusion: 18F-AV-133 had substantial management impact in patients with Clinically Uncertain Parkinsonian Syndromes. This suggests that VMAT2 imaging with 18F-AV133 might improve diagnosis, prognosis and appropriate use of medication, translating into better patient outcomes. Research Support: Supported in part by funds from Avid Radiopharmaceuticals Inc. and the Austin Hospital Medical Research Foundation