Relationship between Neural Rhythm Generation Disorders and Physical Disabilities in Parkinson’s Disease Patients’ Walking

Abstract

Walking is generated by the interaction between neural rhythmic and physical activities. In fact, Parkinson’s disease (PD), which is an example of disease, causes not only neural rhythm generation disorders but also physical disabilities. However, the relationship between neural rhythm generation disorders and physical disabilities has not been determined. The aim of this study was to identify the mechanism of gait rhythm generation. In former research, neural rhythm generation disorders in PD patients’ walking were characterized by stride intervals, which are more variable and fluctuate randomly. The variability and fluctuation property were quantified using the coefficient of variation (CV) and scaling exponent α. Conversely, because walking is a dynamic process, postural reflex disorder (PRD) is considered the best way to estimate physical disabilities in walking. Therefore, we classified the severity of PRD using CV and α. Specifically, PD patients and healthy elderly were classified into three groups: no-PRD, mild-PRD, and obvious-PRD. We compared the contributions of CV and α to the accuracy of this classification. In this study, 45 PD patients and 17 healthy elderly people walked 200 m. The severity of PRD was determined using the modified Hoehn–Yahr scale (mH-Y). People with mH-Y scores of 2.5 and 3 had mild-PRD and obvious-PRD, respectively. As a result, CV differentiated no-PRD from PRD, indicating the correlation between CV and PRD. Considering that PRD is independent of neural rhythm generation, this result suggests the existence of feedback process from physical activities to neural rhythmic activities. Moreover, α differentiated obvious-PRD from mild-PRD. Considering α reflects the intensity of interaction between factors, this result suggests the change of the interaction. Therefore, the interaction between neural rhythmic and physical activities is thought to plays an important role for gait rhythm generation. These characteristics have potential to evaluate the symptoms of PD.

The role of environmental constraints in walking: Effects of steering and sharp turns on gait dynamics

“…LRCs are preserved in the earlier stages of Parkinson’s disease albeit degeneration in the basal ganglia and movement impairments are expressed clearly51. A substantial neural loss in the basal ganglia has typically already occurred in the early stages of Parkinson’s disease when patients receive the first diagnosis52 and cardinal motor symptoms such as reduced stride length and reduced gait velocity are already observable at that stage19.…”

Temporal organization of stride duration variability as a marker of gait instability in Parkinson's disease

“…In the specific context of basal ganglia disorders, Hausdorff et al have already highlighted, in a similar way, such a breakdown of LRA and their strong correlations with neurological impairments in people with Huntington's disease (18). In PD, Ota et al (16) suggested that patients would firstly progress according to an increase in CV stride duration, and secondarily to a decrease in LRA. However, this latter study presents some methodological issue regarding the number of gait cycles collected.…”

“…In the specific context of basal ganglia disorders, strong correlation between the temporal organization of the stride duration variability and Huntington's disease severity was demonstrated by Hausdorff et al (18). In addition, Ota et al studied the interaction between neural rhythm generation disorders and physical abilities in PD, respectively assessed by the stride duration variability and the pull test (16). However, this study presents some specific methodological limitations.…”

“…By extension, the degradation of LRA with pathology was associated with dynamic instability in locomotion (15)(16)(17).…”

“…However, this study presents some specific methodological limitations. On the one hand, Ota et al collected a mean number of stride intervals of 154 strides (SD 23), which appears too short to draw reliable conclusions (16). Indeed, a series length of 256 gait cycles, or, preferably, of 512, is needed to appropriately assess LRA characteristics (11,19).…”