Objective: To investigate the relationship between Parkinson’s disease (PD) motor subtypes and neurodegeneration in both the central and peripheral nervous systems using dopamine transporter single-photon emission computed tomography (DAT SPECT) and a novel sudomotor function test, SUDOSCAN.

Background: PD is characterized by neurodegeneration not only in the central nervous system but also in the peripheral nervous system, including small fiber involvement in the skin due to abnormal α-synuclein accumulation. However, the distribution of these pathological changes is not uniform. PD is classified into multiple motor subtypes, which have been suggested to correlate with disease prognosis. The relationship between motor subtypes and systemic pathological changes remains unclear.

Method: 20 PD patients diagnosed within three years were included in this study. Based on the classification by Kang et al. (2005), patients were categorized into three groups: tremor-dominant (TD, n=8), akinetic-rigid (AR, n=7), and mixed (n=5) subtypes. The specific binding ratio (SBR) of the symptom-dominant hemisphere, measured by DAT SPECT, was used as an index of central neurodegeneration. Peripheral neurodegeneration was assessed using electrochemical skin conductance (ESC) of the hands and feet measured by SUDOSCAN. These parameters were compared among the three groups.

Results: There was no significant difference in SBR of the more-affected side among the three groups. The ESC of the hands was lowest in the AR group and highest in the TD group (TD: 68.0±10.8, Mixed: 52.0±24.7, AR: 42.0±19.1 μS, median±SD). The AR group exhibited significantly lower ESC than the TD group (p=0.027). No significant differences were found between the Mixed and TD or AR groups. Similarly, ESC of the feet was lowest in the AR group and highest in the TD group, but the differences among groups were not statistically significant.

Conclusion: These findings suggest that in early PD, the TD subtype exhibits neurodegeneration relatively confined to the central nervous system, whereas the AR subtype shows more wide-spread neurodegeneration, including peripheral nerve involvement. This study highlights the potential role of peripheral autonomic dysfunction in differentiating motor subtypes of PD and prediction of their disease progression.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/relationship-between-motor-subtypes-and-central-and-peripheral-neurodegeneration-in-early-parkinsons-disease-a-study-using-dat-spect-and-sudoscan/