Management impact of vesicular monoamine transporter (VMAT) imaging with [18F]AV133 in Clinically Uncertain Parkinsonian Syndromes (CUPS).

Objectives Misdiagnosis of Parkinson’s disease initially occurs in up to 30% of patients and in 10-15% after long term follow-up. Dopamine transporter (DAT) SPECT has been shown to change diagnosis in up to 50% of clinically uncertain Parkinsonian syndromes (CUPS). VMAT-II PET imaging with the tetrabenazine derivative, [18F]AV133, provides high quality images of striatal dopaminergic synaptic density with shorter uptake and imaging times than DAT SPECT. We therefore examined the management impact of [18F]AV-133 PET in CUPS.

Methods 47 patients with CUPS were recruited from movement disorder specialists who completed diagnosis and management questionnaires pre and post release of the PET findings. Imaging was acquired for 20 minutes, 2 hours post injection of 250 MBq of [18F]AV133. Images were read visually and quantitatively as ratio of caudate, anterior and posterior putamen to occipital cortex. Change in diagnosis, medication and diagnostic confidence was recorded and rated as nil, low (confirmation of diagnosis), moderate (alteration in management) or high (change in diagnostic class i.e. neurodegenerative PD to other or vice versa).

Results A change in diagnostic class occurred in 14 (30%). Medication change occurred in another 14 (30%). Overall, management impact was rated as moderate or high in 60% of subjects. High clinician diagnostic confidence increased from 3 patients to 35 post scan.

Conclusions [18F] AV133 PET had substantial management impact in patients with clinically uncertain Parkinsonian syndromes, similar to that reported for DAT SPECT, but with the advantage of shorter preparation, uptake and imaging times and the better image quality of PET.