Objective: Aim of this study is to comprehensively compare motor and non-motor symptoms of individuals with Early Onset Parkinson’s Disease (EOPD) with dopamine deficiency to those with scans without evidence of dopamine deficiency (SWEDD).

Background: SWEDD refers to Parkinson’s Disease (PD) patients who display normal presynaptic dopaminergic imaging despite showing symptoms of Parkinsonism. The clinical, imaging, and genetic features of SWEDD are not well understood, leading to uncertainty about whether these patients share similar phenotypic characteristics with those having dopamine-deficient PD.

Method: In our EOPD cohort, we compared motor and non-motor characteristics based on DAT scan (Ioflupane [123I] SPECT) results, differentiating between patients with dopamine deficiency and those without.

Results: Seventy-three case who had a confirmed diagnosis of EOPD and undergone Dat Scan enrolled in the study. Twelve patients (16.4%) were identified as having SWEDD, while 61 exhibited dopamine deficiency. No significant differences were found between the EOPD-SWEDD and EOPD-Dopamine Deficiency groups in terms of disease duration, diagnostic latency, or age at symptom onset. Both groups predominantly presented with a tremor-dominant motor phenotype (58.3% in the EOPD-SWEDD group vs. 68.9% in the EOPD-Dopamine Deficiency group, p = 0.513) and showed no significant differences in clinical motor assessments (no significant difference in Hoehn and Yahr scale and MDS-UPDRS Part II (Motor Aspects of Experiences of Daily Living) and III (Motor Examination) scores at baseline or follow-up. Non-motor symptoms differed significantly between the groups, with the EOPD-SWEDD group exhibiting a higher prevalence of hyposmia (66.7% vs. 21.3%, p = 0.003), cognitive impairment (75% vs. 23%, p < 0.001), sleep disturbances (91.7% vs. 55.7%, p = 0.023), and dementia (33.3% vs. 8.2%, p = 0.035) compared to the EOPD-Dopamine Deficiency group. Furthermore, baseline MDS-UPDRS Part I scores, which evaluate non-motor aspects of daily living, were significantly higher in the EOPD-SWEDD group (17 vs. 7, p = 0.006), indicating a greater burden of non-motor symptoms in these patients.

Conclusion: EOPD patients with SWEDD exhibit motor features comparable to those with dopamine deficiency but are more likely to present with non-motor symptoms.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/scans-without-evidence-of-dopamine-deficiency-swedd-in-early-onset-parkinsons-disease-comprehensive-clinical-analysis/