Impaired Reactive Stepping in Stroke


Introduction

Postural control is required not only for proper body position in space, but is the basis on which movements are organized and executed either via anticipatory or reactive mechanisms. First, the antigravity function of posture provides the mechanical support necessary for the upright position. Second, balance needs to be maintained during movement execution. Third, posture serves as a reference frame for organizing body and limb movements. 

Soon after hospital discharge the individuals with stroke are at increased risk for falls. The ability to react to a balance perturbation is critical to maintain balance and prevent falls. Impaired reactive stepping is a prevalent problem for ambulatory patients with stroke preparing for discharge. Its important to test the capacity to safeguard from fall induced by perturbation and stepping reactions may be important to identify those at risk for falls and to direct appropriate intervention strategies.

Knowledge of the locations of the limbs on the trunk and the head on the trunk is essential for making the correct transformations. To achieve the dual goals of dynamic stability and appropriate orientation during movement, both anticipatory and reactive mechanisms are utilized (Horak et al. 1997; Horak and Macpherson 1996; Massion 1992, 1998; Massion et al. 2004; Shumway-Cook and Woollacott 2001). [1]

Mechanism

Compared to young individuals, elderly subjects more often rely on stepping strategies as opposed to ankle or hip strategies to recover balance following a postural perturbation (Jensen et al. 2001; Maki et al. 2000; McIlroy and Maki 1996). So the ability to initiate a quick and efficient step is a critical factor for postural control in this population.

Stroke patients especially the elderly group demonstrates impaired anticipatory postural adjustments, delays in timing, an inability or unwillingness to initiate a step with the paretic limb, and the use of multi-step responses or the need for assistance to regain stability.

Clinical Assessment

Reactive postural control mechanisms govern the fast, feedback-driven corrections that appropriately redirect foot placement when necessary.

Reactive balance control is less frequently assessed. Reactive stepping can be evaluated by using a "lean-and-release" balance perturbation method. Patients need to wear a safety harness attached to an overhead support, and a physical therapist supervises to ensure safety. [2]

Lean and release.jpg
























Training strategies to improving stepping in people with stroke

1. Neurodevelopmental approaches to improve stepping

The goal of treatment is a normal quality of gait and upper extremity movement. Emphasis is placed on bearing weight and using the extremities on the affected side to prevent learning to compensate with the intact side. As gait training begins, walking is accomplished with the aid of the therapist but without devices or bracing, encouraging the patient to bear weight and walk symmetrically. The philosophy of NDT is summarized in Berta Bobath’s statement that ‘it must always be remembered that the aim of this type of treatment is to improve the quality of movement on the affected side.’ … ‘In order to prepare for a reasonably normal gait, balance, stance and weight transfer should be practiced. If all this is first practiced while in the standing position, [the patient] will develop a better walking pattern than if he is made to walk immediately without the necessary control of his leg.’”

2. Task-Specific Training for Mobility

Salbach et al. (2004) demonstrated task-specific training of lower extremities designed to strengthen the lower extremities and enhance walking balance, speed, and distance showed improvement in a number of gait parameters.

3. Treadmill Training and Partial Weight Support

Treadmill training has been used as a form of gait specific training despite conflicting evidence as to whether or not it is more beneficial than standard gait training. Moseley et al. (2003) conducted a meta-analysis to determine the effectiveness of treadmill training and body weight support for walking after stroke. The authors found that, as compared to other physiotherapy interventions, treadmill training (with and without other task-oriented exercises) had no significant effects on walking speed. Nevertheless, there has been some indication that more aggressive progressive training programs may help to improve the effectiveness of treadmill training. For example, Pohl et al. (2002) found that stroke patients who received structured speed-dependent treadmill training scored significantly higher on measures of walking speed, cadence, stride length, and functional ambulation after 4 weeks of training.

Partial body weight support and treadmill training is a promising new approach that enables non-ambulatory stroke survivors the repetitive practice of complex gait cycles rather than single limb gait preparatory manoeuvres.

4. Functional Electrical Stimulation in the Lower Extremity

Functional electrical stimulation (FES) in the lower extremity has been used to enhance ankle dorsiflexion during the swing phase of gait. Weak ankle dorsiflexion with plantarflexion hypertonicity results in a drop foot, which is typically corrected by an ankle foot orthosis (AFO). FES of the common peroneal nerve during the swing phase of gait would appear to be a suitable alternative. Although not widely used or universally available, for highly motivated patients, able to walk independently or with minimal assistance, there is growing evidence that treatment with FES can improve dropped foot, which in turn can improve gait. Both implantable and surface electrodes may be used. A meta-analysis by Glanz et al. (1996) including four RCTs (Bowman et al. 1979, Winchester et al. 1983, Merletti et al. 1978, Levin 1992), reported a favourable treatment effect associated with FES compared to a no treatment control. The effect size associated with a statistically significant change in paretic muscle force of contraction was 0.63 (95% CI 0.29, 0.98), although the clinical significance of this outcome is unclear. There were no other common outcomes among the four included studies.

Recent Related Research (from Pubmed)

Failed to load RSS feed from http://www.ncbi.nlm.nih.gov/entrez/eutils/erss.cgi?rss_guid=1TCb4A3LOGbUsLDKj9LC: There was a problem during the HTTP request: 500 Internal Server Error

References

  1. Shih-Chiao Tseng, Doctor of Philosophy, 2008 Impaired reactive postural control in the elderly during voluntary stepping.
  2. Inness EL, Mansfield A, Lakhani B, Bayley M, McIlroy WE.Impaired reactive stepping among patients ready for discharge from inpatient stroke rehabilitation.Phys Ther. 2014 Dec;94(12):1755-64. doi: 10.2522/ptj.20130603. Epub 2014 Aug 7.