Objective: To evaluate the relationship between gait asymmetry and the integrity of the corpus callosum connecting sensorimotor cortical regions in people with idiopathic Parkinson’s Disease (PD) and healthy controls (HC).

Background: Transcallosal communication via the corpus callosum between the brain hemispheres plays a key role in the production of integrated motor behavior to generate appropriate, coordinated motor responses on both sides of the body. In PD, the supraspinal control of locomotion is altered and the need for additional volitional neural control contributes to an increase in gait asymmetry.

Methods: Ten PD (Hoehn & Yahr 2-4) and 8 HC underwent high-angular resolution diffusion imaging (HARDI; Siemens Tim Trio 3T Scanner). White matter microstructural integrity of transcallosal fibers connecting homologous sensorimotor cortical regions [primary motor (M1) and somatosensory (S1) cortices, and pre-supplementary motor (PSMA) and supplementary motor areas (SMA), respectively] was assessed. Spatial and temporal gait asymmetry was assessed via wireless inertial sensors (APDM) and an instrumented walkway (GAITRite). Three walks at preferred gait speed were used to determine step length asymmetry and step time asymmetry. We correlated fractional anisotropy (FA) of the callosal regions of interest with gait asymmetry metrics where group performance was different.

Results: Preliminary results show a significant group difference in step length asymmetry, but not for step time asymmetry. PD showed significantly greater step length asymmetry compared to HC. In addition, we report a strong relationship between step length asymmetry and callosal fiber tract integrity (FA) connecting the primary motor cortices (M1: r=-0.37) and the primary somatosensory cortices (S1: r=-0.48). These were also the only sensorimotor callosal regions that demonstrated group differences in white matter integrity: M1 (PD: 0.43 (0.08); HC: 0.48(0.05)) and S1 (PD: 0.36 (0.08); HC: 0.47 (0.05)). 

Conclusions: PD showed significantly increased step length asymmetries and decreased microstructural integrity of callosal white matter tracts connecting M1 and S1. These measures were also strongly associated with each other, indicating that reduced transcallosal structural connectivity may be a significant mechanism underlying bilateral asymmetries in those with PD. Data collection and analyses in a larger sample is on-going.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/gait-asymmetry-in-people-with-parkinsons-disease-is-linked-to-reduced-integrity-of-callosal-sensorimotor-regions/