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.

Motor strategies of postural control after hemispheric stroke.

After stroke, the causes of balance disorders include motor disorders, sensory loss, perceptual deficits and altered spatial cognition. This review focuses on motor strategies for postural control after stroke. Weight-bearing asymmetry, smaller surface of stability, increased sway, body tilting and sometimes pushing syndrome are observed. Weakness and sensory impairments account only for some of these disturbances; altered postural reactions and anticipated postural adjustments as well as abnormal synergistic muscular activation play an important part. These disorders are often linked to cognitive impairments (visuospatial analysis, perception of verticality, use of sensory information, attention, etc.), which explain the preeminent disorders of postural control seen with right rather than left-hemisphere lesions. Most of the motor changes are due to an impaired central nervous system but some could be considered adaptive behaviors. These changes have consequences for rehabilitation and need further studies for building customized programs based on the motor comportment of a given patient.

Sensory reweighting in controls and stroke patients.

OBJECTIVE: To test sensitivity to proprioceptive, vestibular and visual stimulations of stroke patients with regard to balance. METHOD: The postural control of 20 hemiparetic patients after a single hemispheric stroke that had occurred at least 6 months before the study along with 20 controls was probed with vibration, optokinetic, and vestibular galvanic stimulations. Balance was assessed using a force platform (PF) with two miniature inertial sensors placed on the head (C1) and the trunk (C2) under each sensory condition and measured by three composite scores as the mean displacement of the body (PF, C1, C2) during the stimulation. A subject with a composite score greater than the 75th percentile of the composite scores found in the control subjects was arbitrarily considered to be sensitive to that stimulation. RESULTS: Both control and stroke patients showed large inter-individual variations in response to the three types of sensory stimulation. Among the hemiparetic patients, nearly 65% were sensitive to the optokinetic stimulation, 60% to the galvanic stimulation and 65% to the vibration stimulation. In contrast to the control group, all the hemiparetic subjects were sensitive to at least one type of stimulation. CONCLUSION: Stroke patients are highly dependent on visual, proprioceptive and vestibular information in order to control their standing posture and individually differ in their relative sensitivity to each type of sensory stimulation. SIGNIFICANCE: Contrarily to what one might suppose, the increased visual dependence manifested by stroke patients does not necessarily entail any neglect of proprioceptive and vestibular information.

Influence of subjective visual vertical misperception on balance recovery after stroke.

BACKGROUND: Subjective visual vertical (SVV) perception can be perturbed after stroke, but its effect on balance recovery is not yet known. AIM: To evaluate the influence of SVV perturbations on balance recovery after stroke. METHODS: 28 patients (14 with a right hemisphere lesion (RHL) and 14 with a left hemisphere lesion (LHL)) were included, 5 were lost to follow-up. SVV perception was initially tested within 3 months after stroke, then at 6 months, using a luminous line, which the patients adjusted to the vertical position in a dark room. Mean deviation (V) and uncertainty (U), defined as the standard deviation of the SVV, were calculated for eight trials. Balance was initially assessed by the Postural Assessment Scale for Stroke (PASS), and at 6 months by the PASS (PASS6), a force platform (lateral and sagittal stability limits (LSL6 and SSL6)), the Rivermead Mobility Index (RMI6) and gait velocity (v6). Functional outcome was also assessed by the Functional Independence Measure at 6 months (FIM6). RESULTS: The scores for balance and for FIM6 were related to the initial V value: PASS6 (p = 0.01, tau = -0.38); RMI6 (p = 0.002, tau = -0.48), LSL6 (p = 0.06, tau = -0.29), SSL6 (p = 0.004, tau = -0.43), v6 (p = 0.01, tau = -0.36) and FIM6 (p = 0.001, tau = -0.49), as well as to the initial U value: PASS6 (p = 0.03, tau = -0.32), RMI6 (p = 0.02, tau = -0.35), SSL6 (p = 0.005, tau = -0.43) and FIM6 (p = 0.01, tau = -0.38). CONCLUSIONS: Initial misperception of verticality was related to a poor score for balance after stroke. This relationship seems to be independent of motricity and neglect. Rehabilitation programmes should take into account verticality misperceptions, which could be an important factors influencing balance recovery after stroke.

Evolution of subjective visual vertical perturbation after stroke.

OBJECTIVE: The perception of visual verticality is often perturbed after stroke and might be an underlying component of imbalance. The aim of this study was to describe the evolution of visual vertical (VV) perturbation and to investigate the factors affecting it. METHODS: Thirty patients with hemiplegia after a single hemispheric stroke (17 left lesioned [LL] and 13 right lesioned [RL]) were studied. Visual verticality was tested within 45 days of stroke, and then at 3 and 6 months. Subjects sat in a dark room and adjusted a luminous rod to the vertical position. The differences between patients' adjustments and vertical were calculated. The effects on VV evolution of the side, size, type, and location of the lesion were tested. RESULTS: Sixty percent of the recent stroke patients had an initial inaccurate perception of verticality, and 39% of these patients recovered during the 1st 3 months after stroke. The evolution of VV tilt depended on the side of the lesion (P = 0.01), with better recovery in LL patients. None of the other factors studied affected VV normalization. CONCLUSIONS: The poorer recovery of vertical perception after right-side stroke might be due to the predominant role of the right hemisphere in spatial cognition, and might be involved in the poorer recovery of balance after stroke in RL patients.

Postural visual dependence after recent stroke: assessment by optokinetic stimulation.

INTRODUCTION: This study was conducted to assess visual dependence of postural control early after stroke. DESIGN: Case control study. SETTING: A Physical Medicine and Rehabilitation Department. METHOD: Twenty-five patients impaired by severe hemiplegia due to a recent first stroke, were examined. Fourteen had a right and 11 a left hemispheric lesion. There were aged 52+/-13 years, time since stroke was 30+/-12 days. Patients' data were compared to data for 25 healthy subjects. Sitting posture was assessed on a dynamic balance, using two parameters: frontal plane displacement of the centre of pressure under optokinetic stimulation (OKS), and the total length of centre of pressure displacement for the stability reaction. On the basis of 90th percentile control data, patients' behaviour was classified as totally visuo independent (VI), totally visuo dependent (VD) or mixed. RESULTS: Body tilt under OKS was greater in patients than controls. No control subject was totally VD, 19 subjects were totally VI. Four patients were totally VD and only six were VI. The only clinical parameter linked to the effect of OKS was the sensitivity impairment. Overall patients with visuospatial neglect were the most perturbed, but two were totally visuo independent. DISCUSSION AND CONCLUSION: Assessment of postural variations in sitting under OKS is proposed for estimating visual dependence early after stroke. Individual reactions are more important than mean group reactions. Visual dependence is not solely due to neurological impairment, implying that previous physiological behaviour may be involved. Knowledge of these characteristics may affect rehabilitation programmes.

[Post stroke hemiplegia: lower limb benefit from botulinum toxin (review)]. / Hémiplégie vasculaire: membre inférieur et toxine botulique (Revue).

OBJECTIVE: To clarify the conditions governing the use of botulinum toxin (BTX) for post-stroke lower limb spastic disorders: indications, choice of muscles, doses, and duration of efficacy. METHOD: Review of the international literature using the Medline and the Reedoc data banks. RESULTS: Seven controlled studies were reviewed, including in particular 2 studies vs placebo and one vs phenol, 7 open studies or case series closely related to this topic and 4 open studies partly dedicated to it. The usefulness of BTX for the treatment of equinovarus has been demonstrated. The main muscles to be treated are the soleus, gastrocnemius and tibialis posterior. The treatment proposed for toe clawing is BTX injection into the flexor digitorum longus and flexor hallucis longus, and for great toe permanent extension, injection of the extensor hallucis longus. The quadriceps femoris, the tibialis anterior or the hamstrings have only be treated in isolated cases. When the treatment is effective, its benefit may last for more than 6 months. DISCUSSION: A few controlled trials have demonstrated the efficacy of BTX for post stroke lower limb spasticity. The results of all the controlled and open trials argue in favor of its efficacy, but this still requires more thorough analysis. CONCLUSION: Botulinum toxin has a place together with other local treatments for post-stroke spasticity, but a precise guide to its use, especially its dosage, and it's effectiveness compared to that of other treatments, need further study.