Objective: This study aimed to evaluate the utility of ¹⁸F -DOPA PET in patients with diagnostic uncertainty at our movement disorder clinic in India.

Background: Parkinson’s disease (PD) has several mimics including tremor disorders [1]. ¹⁸F -DOPA PET measures the uptake of dopamine precursors for assessment of presynaptic dopaminergic integrity [2]. This aids in differentiating PD from non-parkinsonian disorders, particularly in early PD. This is especially useful in patients with spinocerebellar ataxia type 12 (SCA12) which is common in the North Indian population, who often experience a delayed diagnosis due to late ataxia years after initial tremors or parkinsonism. ¹⁸F -DOPA PET can assist in treatment decision for patients with drug-induced Parkinsonism as certain drugs can unmask pre-symptomatic PD.

Method: A retrospective chart review was conducted on patients attending a movement disorder clinic who underwent ¹⁸F -DOPA PET over the last two-year study period.

Results: During the study period, 62 patients underwent ¹⁸F -DOPA PET, comprising 37 males (59.68%) and 25 females (40.32%). Overall mean age ± SD was 62.79 ± 11.85 years, with females having a slightly higher mean age (63.52 ± 12.25 years) compared to males (62.30 ± 11.72 years). The included patient cohort consisted of atypical parkinsonism (n=27), ataxia-tremor-parkinsonism (n=15), essential tremor-plus (n=10), drug-induced parkinsonism (n=6), and dystonic tremor with rest tremor (n=3) and extrapontine myelinolysis (n=1). Among these, ¹⁸F -DOPA PET positivity rates were as follows: atypical parkinsonism (n=18/27, 66.66%), ataxia-tremor-parkinsonism (n=3/15, 20%), essential tremor-plus (n=1/10, 10%), drug-induced parkinsonism (n=1/6, 16.66%), and dystonic tremor with rest tremor (n=0/3, 0%) and extrapontine myelinolysis (n=0/1, 0%).

Conclusion: In this study, ¹⁸F -DOPA PET was most predictive for atypical parkinsonism followed by ataxia-tremor-parkinsonism, drug-induced parkinsonism and ET plus. This was particularly useful in distinguishing SCA12 from PD. A limitation of this study was the small sample size, as only a subset of patients with diagnostic uncertainty were included. However, the findings underscore the utility of ¹⁸F -DOPA PET in refining clinical diagnoses and guiding management decisions in a movement disorder clinic setting.

References: 1.Ibrahim N, Kusmirek J, Struck AF, Floberg JM, Perlman SB, Gallagher C, Hall LT. The sensitivity and specificity of F-DOPA PET in a movement disorder clinic. Am J Nucl Med Mol Imaging. 2016 Jan 28;6(1):102-9. PMID: 27069770; PMCID: PMC4749509.
2.Pavese N, Brooks DJ. Imaging neurodegeneration in Parkinson’s disease. Biochim Biophys Acta. 2009;1792:722–729. doi: 10.1016/j.bbadis.2008.10.003.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinical-profile-and-18f-fluorodopa-positron-emission-tomography-18f-dopa-pet-findings-in-a-movement-disorder-clinic-patient-cohort/