Difference between individuals with left and right hemiparesis in the effect of gluteus medius vibration on body weight shifting.

OBJECTIVE: To test the effect of gluteus medius (GM) vibration on the reduction of asymmetric body weight distribution in individuals with hemiparesis (HP) at two stages of postural recovery. METHODS: The effects of GM vibration according to the shift of the body weight (%Shift) onto the paretic leg during GM vibration were registered while standing on a force-platform in 40 HP (19 left and 21 right; mean age 54.7±10.6years, mean time after stroke 2.0±1.3months), as soon as they could stand without assistance and 4 to 6 weeks later, and in 40 control subjects (mean age 54.7±10.5years). RESULTS: Without vibration, baseline body weight (BW) distribution was characterized by underloading of the paretic limb (mean BW on the paretic limb 37.2%±13.1%). At the early stage of balance recovery, % shift toward the paretic limb induced by GM vibration differed significantly between left and right HP (P=0.049) and between left HP and controls (C) (P=0.022) and was related to BW asymmetry (r=0.437, P=0.004). Later, GM vibration reduced asymmetric BW distribution in most HP and no difference was found between left and right HP and between left and C. CONCLUSION: At an advanced stage of postural recovery, GM vibration could help encourage HP to put weight on the affected limb. Interestingly, a behavioral difference was initially observed between right and left HP that could probably be explained by a different strategy due to the baseline severity of the BW asymmetry.

The effect of optokinetic and galvanic vestibular stimulations in reducing post-stroke postural asymmetry.

OBJECTIVE: To investigate the postural effect of 2 types of sensory stimulation in patients with a left hemispheric lesion (LHL) or right hemispheric lesion (RHL) compared with controls. METHODS: 35 patients (18 LHL, 17 RHL) and 27 controls (mean age 54.1 years), with a mean delay post-stroke of 3.0 months were enrolled. Subjects stood on a force platform and were stimulated on the left and right side by optokinetic (Okn) and galvanic vestibular (Gv) stimulation. Lateral displacement following stimulation toward the right and left directions was calculated as the mean position of the centre of pressure (CP) during the stimulation period minus the mean position at rest. RESULTS: Postural asymmetry was reduced in LHL and RHL patients. CP displacement was higher in cases of left-sided stimulation in the RHL group compared with control subjects and LHL patients (respectively 2.8 and 2.4 times higher, group effect, p<0.001, group × direction of stimulation interaction, p=0.007). The magnitude of displacement under Okn significantly correlated with Gv in all cases (ρ=0.635, p<0.001). CONCLUSIONS: Both GV and Okn stimulations can modulate hemiparetic's CP and their postural effects are correlated. SIGNIFICANCE: Results support a high level cortical postural effect of sensory stimulation on supramodal spatial network.

Effect of sensorial stimulations on postural disturbances related to spatial cognition disorders after stroke.

Balance disorders related to disturbances in perception of spatial reference systems are common especially after right hemispheric stroke. Mental misrepresentation of bodily orientation in space is then often superimposed upon other factors affecting imbalance such as motor and sensory impairments. Traditional rehabilitation for balance recovery has not been specifically designed to improve balance disorders related to spatial cognition. The traditional approach, consisting of stimulating the conscious perception of body orientation in space, is demanding and laborious. The approach based on sensorial stimulation is completely different. The relevance of this method lies in the fact that, firstly it is specifically active in the cognitive component of balance disorders; and secondly, it can passively be applied with minimal patient participation, which is of particular importance for this patient group characterized by disorders of attention and concentration. These techniques, such as proprioceptive, visual or vestibular stimulation, have been found to correct spatial neglect but also postural bias. Clinical and data from functional neuro-imaging suggest a direct central action on cortical structures involved in the elaboration of spatial representation. These are promising techniques for the rehabilitation of postural disturbances related to spatial cognition disorders but are as yet at the stage of preliminary results.