Impacts of freezing of gait on forward and backward gait in Parkinson’s disease

Highlights

• Forward gait was similar between freezers and non-freezers except for gait speed.

• Freezers showed marked difference at backward gait from non-freezers.

• Further studies of backward gait would help our understanding of gait freezing.

Abstract

Freezing of gait (FOG) is a major risk factor for falls and fall-related injuries in patients with Parkinson’s disease (PD). The characteristics of gait in PD patients with FOG have been studied but remain controversial. To investigate gait characteristics of FOG in PD, this study analyzed the forward and backward walking of patients with PD. Twenty-six patients with PD were recruited [age: 71.0 ± 6.2 years, Hoehn and Yahr stage: 2–3 (median 2.5)]. Based on responses to the New Freezing of Gait Questionnaire, we classified patients into either the “freezer” or “non-freezer” group. Spatiotemporal and kinematic analyses of forward and backward walking were completed using a three-dimensional motion analysis system over an 8 m walkway in the defined “off” state. There was no difference in demographic and clinical characteristics between the freezers (n = 10) and non-freezers (n = 16). Analysis of forward walking revealed no between-group differences, except for faster walking speed among the non-freezers. During backward walking, the freezers exhibited slower walking speed, shorter stride length, and increased asymmetry of step length. Kinematic analysis of backward walking revealed smaller range of motion in hip and ankle joints and lower step height in freezers. Further investigations of backward walking might expand our understanding of the pathophysiology of FOG in patients with PD.

Introduction

Freezing of gait (FOG) is defined as suddenly stopping or decreased stepping in spite of the intention to continue walking. It frequently occurs in patients with Parkinson’s disease (PD), with an estimated point prevalence of 30–60% [[1], [2]]. FOG is related to postural instability and balance impairment and is a major risk of falling while walking [[3], [4]]. Falls resulting from FOG can cause serious trauma and impose considerable social burden [5]. FOG can be provoked at the start of gait, turning, passing narrow paths or obstacles, approaching target destinations, or under stressful conditions [[6], [7]]. Patients with PD often experience gait adjustment difficulties in response to environmental changes or complex directional control [8], and FOG can be provoked by such conditions.

Walking is the key component of human locomotion, and walking backward is a natural, but complex variation of forward walking [9]. Backward walking is an essential component of numerous daily activities including changing clothes or turning in narrow spaces. It is frequently associated with backward sway or perturbation and frequently causes falls in elderly people [[8], [10], [11]]. Patients with PD demonstrate impairments in gait control during complex locomotive tasks, including turning, and gait analysis in patients with PD should include multi-directional walking tasks [8].

Compared to normal elderly people, patients with PD are more dependent on visual feedback to control posture and gait, which can be contributed by defective proprioception in PD [[12], [13], [14]]. Those visual dependence in PD are shown to be excessive in patients with FOG, resulting in FOG events at confronting obstacles or narrow paths [[13], [14], [15]]. Because backward walking is usually performed without visual information and is complex locomotive task, PD patients with FOG might have greater difficulty in backward walking.

Several studies have characterized backward walking in patients with PD. Some studies have indicated that patients with PD walk slower, in both forward and backward directions, than control subjects [[8], [16]]. Compared to forward walking, backward walking in the “off” state was slower with shorter stride length. However, there are no differences between forward and backward walking in the “on” state [17]. Patients with PD having FOG exhibited slower forward and backward walking, with shorter stride length and higher gait asymmetry during backward walking than those without FOG [10].

Although past studies have described some characteristics of backward walking in patients with PD, they studied only the two-dimensional analysis of gait. Comprehensive characterization of backward walking using three-dimensional kinematic analysis has not been done in patients with PD. And the influence of FOG on backward walking in patients with PD was also not fully investigated. Therefore, this study analyzed forward and backward walking in patients with PD to investigate the impact of FOG using a three-dimensional kinematic analysis system. Our hypothesis is that PD patients with FOG have greater impairments in walking than those without FOG, especially at backward walking.