Evaluation of a visual biofeedback on the postural control in Parkinson's disease.

OBJECTIVES: Both stabilization and orientation components of postural control are affected in Parkinson's disease (PD). These deficits are partly due to proprioceptive impairments, which frequently coexist with a visual dependence. This study aimed to evaluate if a visual biofeedback - i.e. real time anteroposterior trunk and head orientations indicated with a simplified avatar and represented in a head-mounted display - could improve the postural control of PD patients in response to a postural disturbance. The influence of focusing on one specific component of the postural control (stabilization or orientation) was also examined. METHODS: Seventeen medicated PD patients performed sequences of pull-tests, either with eyes open, eyes closed or visual biofeedback, crossed with the verbal instruction to focus either on the stabilization or on the vertical body orientation. Kinematics data were collected. RESULTS: Backward trunk tilts consequent to the pulls were unchanged across the different conditions. With eyes open and eyes closed, patients did not recover their initial vertical orientation by adopting a slightly tilted backward position. This bias disappeared with the visual biofeedback. Moreover, falls consecutive to the test were significantly less frequent with the visual biofeedback than in the two other visual conditions. These different orientation and stabilization parameters were not affected by the instruction. CONCLUSION: Unlike a verbal instruction, visualizing in real time their own body's geometry improved both components of postural control of PD patients. This provides evidences in PD about links between impaired vertical orientation, deficits in balance control, and contribution of supplementary sensory cues.

[Pulsatile echography (ultrasonic cerebral tomosphygmography) in carotid and vertebral pathology. Surgical applications]. / L'échographie pulsatile (tomosphygmographie cérébrale ultrasonore) en pathologie carotidienne et vertébrale. Applications chirurgicales.

Ultrasonographic cerebral tomosphygmography (U.C.T.S.) is a method for determining cerebral pulsatility by centimeter-thick sections. The prototype uses a 2 MHz ultrasound wave emitted in the direction of cerebral structures. The reflected wave is captured by centimeter-thick sections, the mean determined and a pulsatile index defined. This index varies according to the regions studied (cortico-subcortical, superficial sylvian, deep sylvian and vertebrobasilar). Physiologic pulsatility was determined from a series of 150 healthy subjects. This technique was used to evaluate effects of carotid and vertebral circulation revascularization in 21 patients. Findings showed lack of relation between anatomic lesion and cerebral pulsatility, absence of significant modification of the index after release of carotid occlusion except when postoperative thrombosis occurred, and heterogeneous individual behavior after revascularization distinguishing subgroups of indifferent (40%), improved (27%), hyperpulsatile (27%) and worsened (13%) subjects. Two patients presented worsening on the contralateral side compatible with a steal syndrome. Results suggest that U.C.T.S. is a promising method of preoperative investigation and postoperative surveillance of carotid artery stenosis.