Arm swing as a potential new prodromal marker of Parkinson's disease.

BACKGROUND: Reduced arm swing is a well-known clinical feature of Parkinson's disease (PD), often observed early in the course of the disease. We hypothesized that subtle changes in arm swing and axial rotation may also be detectable in the prodromal phase. OBJECTIVE: The purpose of this study was to evaluate the relationship between the LRRK2-G2019S mutation, arm swing, and axial rotation in healthy nonmanifesting carriers and noncarriers of the G2019S mutation and in patients with PD. METHODS: A total of 380 participants (186 healthy nonmanifesting controls and 194 PD patients) from 6 clinical sites underwent gait analysis while wearing synchronized 3-axis body-fixed sensors on the lower back and bilateral wrists. Participants walked for 1 minute under the following 2 conditions: (1) usual walking and (2) dual-task walking. Arm swing amplitudes, asymmetry, variability, and smoothness were calculated for both arms along with measures of axial rotation. RESULTS: A total of 122 nonmanifesting participants and 67 PD patients were carriers of the G2019S mutation. Nonmanifesting mutation carriers walked with greater arm swing asymmetry and variability and lower axial rotation smoothness under the dual task condition when compared with noncarriers (P < .04). In the nonmanifesting mutation carriers, arm swing asymmetry was associated with gait variability under dual task (P = .003). PD carriers showed greater asymmetry and variability of movement than PD noncarriers, even after controlling for disease severity (P < .009). CONCLUSIONS: The G2019S mutation is associated with increased asymmetry and variability among nonmanifesting participants and patients with PD. Prospective studies should determine if arm swing asymmetry and axial rotation smoothness may be used as motor markers of prodromal PD. © 2016 International Parkinson and Movement Disorder Society.

Exploring cancer in LRRK2 mutation carriers and idiopathic Parkinson's disease.

Objectives: To compare the risk of non-skin cancer in LRRK2 mutation carriers and individuals with idiopathic Parkinson's disease (iPD), explore the age at which LRRK2 mutation carriers have cancer compared to iPD subjects, and clarify whether certain cancers are more closely associated with the LRRK2 mutation than iPD. Materials and Methods: Demographic data and cancer outcomes from 830 iPD patients and 103 LRRK2 mutation carriers (27 with PD) were retrospectively collected. Oncologic data were obtained from the Cancer Registry of Norway and included cancer type and age at cancer. All study participants were of Norwegian ethnicity. Results: LRRK2 mutation carriers have increased risk of non-skin cancer compared with iPD subjects (OR 2.09; 95% CI 1.16-3.77; p = .015). A significant association was found between the mutation and breast cancer in women (OR 4.58; 95% CI 1.45-14.51; p = .010). No other associations between harboring a LRRK2 mutation and specific cancer types were uncovered. Conclusion: LRRK2 mutation carriers have an increased risk of non-skin cancer compared with iPD subjects, which was mainly driven by the association between harboring the mutation and breast cancer in women. The increased risk is likely independent of ethnicity.