Purpose It is often difficult to differentiate parkinsonism,especially when patients show uncertain parkinsonian features.
We investigated the usefulness of dopamine transporter(DAT) imaging for the differential diagnosis of inconclusiveparkinsonism using [18F]FP-CIT PET.
Methods Twenty-four patients with inconclusive parkinsonianfeatures at initial clinical evaluation and nine healthycontrols were studied. Patients consisted of three subgroups:nine patients whose diagnoses were unclear concerningwhether they had idiopathic Parkinson’s disease or druginducedparkinsonism (‘PD/DIP’), nine patients who fulfilledneither the diagnostic criteria of PD nor of essential tremor(‘PD/ET’), and six patients who were alleged to have eitherPD or atypical parkinsonian syndrome (‘PD/APS’). BrainPET images were obtained 120 min after injection of185 MBq [18F]FP-CIT. Imaging results were quantified andcompared with follow-up clinical diagnoses.
Results Overall, 11 of 24 patients demonstrated abnormallydecreased DAT availability on the PET scans, whereas 13were normal. PET results could diagnose PD/DIP and PD/ET patients as having PD in six patients, DIP in seven, and ETin five; however, the diagnoses of all six PD/APS patientsremained inconclusive. Among 15 patients who obtained afinal follow-up diagnosis, the image-based diagnosis wascongruent with the follow-up diagnosis in 11 patients. Fourunsolved cases had normal DAT availability, but clinicallyprogressed to PD during the follow-up period.
Conclusion [18F]FP-CIT PET imaging is useful in the differentialdiagnosis of patients with inconclusive parkinsonianfeatures, except in patients who show atypical features orwho eventually progress to PD.