Transverse Strips Instead of Wearable Laser Lights Alleviate the Sequence Effect Toward a Destination in Parkinson's Disease Patients With Freezing of Gait

Abstract

Background: The sequence effect (SE), referring to step-to-step reduction in amplitude, is considered to lead to freezing of gait (FOG) in Parkinson's disease (PD). Visual cues may alleviate SE and help reduce freezing episodes. FOG patients show significant SE prior to turning or toward a doorway, but the SE toward a destination has not been clearly studied. Objectives: To examine the SE when approaching a destination in PD patients with FOG, and to further explore the effects of different types of visual cues on destination SE. Methods: Thirty-five PD patients were divided into a freezing (PD+FOG, n = 15) group and a non-freezing (PD-FOG, n = 20) group. Walking trials were tested under three conditions, including without cues (no-cue condition), with wearable laser lights (laser condition), and with transverse strips placed on the floor (strip condition). Kinematic data was recorded by a portable Inertial Measurement Unit (IMU) system. The destination SE and some key gait parameters were evaluated. Results: The PD+FOG group showed greater destination SE in the no-cue and laser conditions when compared to the PD-FOG group. There were no significant differences in the strip condition when comparing destination SE of the two groups. The destination SE was alleviated only by using the transverse strips on the floor. In contrast, transverse strips and wearable laser lights could increase the step length. Conclusions: The significant destination SE may explain why FOG patients are prone to freezing when heading toward their destination. Visual cues using transverse strips on the floor may be a more effective strategy for FOG rehabilitation in PD patients.

The Effects of Intensive Neurorehabilitation on Sequence Effect in Parkinson's Disease Patients With and Without Freezing of Gait

“…The dSE is a physiological step-by-step reduction in step length that occurs when a subject approaches the end of gait, probably representing a safety strategy toward a planned gait termination (15). dSE may become pathological when particularly pronounced as in PD and specifically in patients with FOG (16)(17)(18).…”

“…The dSE was computed as a regression slope (β) of step length according to a previously described and validated methodology where step length is plotted against step number (16)(17)(18). The regression slope represents the decrease (negative values) or increase (positive values) in step length.…”

“…As previously described, the last stride was excluded to avoid interference of sharp deceleration before gait ending. The length of the last six steps (y) ahead of the final stride was then plotted against step number (x), and the linear regression slope (β) was calculated as a measure of dSE (16)(17)(18)26). In addition, the intercept (I) of the regression curve was used as an indirect measure of gait hypokinesia (17,18).…”

“…The sequence effect (SE), defined as a reduction in amplitude of repetitive movements, is a common clinical feature of several tasks of PD patients both in early and advanced stages of the disease (12)(13)(14). During walking, SE manifests as a stepby-step reduction in step length when approaching a turning point or gait destination resulting in the so-called destination sequence effect (dSE) (15,16). Experimental and clinical evidence supports the hypothesis that SE is a contributor to FOG (17,18).…”

“…Indeed, the dual requirement hypothesis suggests that FOG may be precipitated by the occurrence of SE over a constitutional reduction of stride length (gait hypokinesia) (17,19). SE is specifically pronounced in PD patients affected by FOG, and it arises immediately before a FOG episode induced by a turning or a dual-task (16). SE may be triggered by several factors, such as an obstacle, a cognitive task, or removal of visual or integrative cues (20)(21)(22).…”