Objective: To study the clinical onset and progression of motor manifestations in different body regions in early PD patients.

Background: The vulnerability of the nigrostriatal dopaminergic system in Parkinson’s disease (PD) follows a topography pattern, with the earliest and highest dopamine depletion occurring in the putaminal posterodorsal area. This area corresponds with the representation of the foot. The motor signs of PD should be more evident in this area of the body and later affect the upper extremity and face. But, early motor features of PD seem to begin most intensely in the upper limbs.

Method: Drug näive PD patients were included in a prospective longitudinal study. Eligibility criteria: unilateral motor manifestations and less than 18 months since diagnosis. Twenty‑one age and gender‑matched healthy subjects (HS) were enrolled. The most affected body region was determined using various standards: the patient and neurologist reports;  MDS‑UPDRS scale and objective quantitative metrics of motor function with inertial measurement units (Kinesia system). Non‑parametric tests were used to compare the motor assessment of the different body sides between PD patients and HS.

Results: Twenty‑one drug naïve PD patients were included. Mean disease duration since diagnosis was 12 months. No differences were found in sociodemographic features between PD patients and HS. The large majority of patients, 90.5% reported upper limb impairment as the most affected region at onset. Upper limb predominant involvement was confirmed by both neurological examination (91%) and the MDS‑UPDRS score (86%). The kinematic analyses reflected that all. PD patients have significant (i.e. reduced) differences in acceleration and rotation amplitude in the upper limbs’s  tasks, even for those fewer patients who showed predominantly affected the lower limbs (14%). The quantitative measurement showed that upper limbs performance was more affected than the lower limbs in PD patients (p<0.05). Agreement among the different measured parameters (81%), confirmed upper limb predominant motor impairment.

Conclusion: These findings showed after an objective evaluation that PD patients exhibit upper limb motor dysfunction first. The discrepancy with data suggesting a dorsal putaminal denervation preference at onset needs further exploration, but we hypothesize that the upper limb motor function has a lower dopamine striatal threshold than the lower limb.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/motor-onset-of-parkinson%ca%bcs-disease-is-there-a-somatotopic-pattern/