Perceived Body Vertical in Standing Patients with Stroke

Alexander Aruin
Physical Therapy, University of Illinois at Chicago

Noel Rao
Marianjoy Rehabilitation Hospital, Wheaton, IL

Lew Nashner
NeuroCom International

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     Last modified: March 14, 2007

Abstract
The ability to maintain posture requires the integration of information from vestibular, visual, and propreoceptive systems. In patients balance can be affected by many factors including misperception of the visual information, a factor that is commonly found in individuals with visuospatial neglect resulting from cerebral hemispheric stroke. One manifestation of this condition is impaired perception of the position of the body in space, represented by a several degrees tilt of the perceived visual vertical of the body. The assessment of perceived body verticality is usually performed in a dark room when seated subjects manually adjust a luminous rod to the vertical position. However, this protocol is limited to sitting conditions only. Recently we developed a new method that involves assesment of the perceived body vertical in the frontal and sagittal planes while in standing. The method is based on using a modified NeuroCom Computerized Dynamic Posturography technique combined with the Biodex Unweighing System. The method was tested in eight individuals who sustaned a stroke and who exhibited neglect of their hemiparetic side in conjunction to visuospatial problems (26.815.7 days post-stroke, 6 presented with right hemiparesis and 2 with left hemiparesis) and eight healthy control subjects. The subjects were provided with a harness system (that allowed partial support of their body weight if needed) and were required to identify the perceived verticality of their body in relation to the position of the platform on which they were standing. This was completed as the platform was returning back (velocity 1 deg/sec) to a horizontal position after being tilted in a toes up/down or left/right direction by 5 degrees. Platform tilts induced changes in the body verticality either in sagittal or frontal plans. Each subject participated in eight trials and was instructed to identify the moment when he/she felt the body was vertical. Subsequentially, angles between the platform position in sagittal and frontal planes in relation to the horizontal plane were measured. These angles in the sagittal plane were 1.930.42 deg. in patients and 0.630.27 deg. in controls (P<0.01). Mean angles in the frontal plane were 1.730.53 and 0.560.05 deg in patients and controls respectivelly (P<0.05). The results of the study demonstrate that patients identified perceived body vertical aproximately three times worse than control subjects (P<0.05). The outcome of the study suggests that objective measurement of perceived verticality in standing should be used when designing appropriate treatment protocols and monitoring the progress of the rehabilitation of patients with stroke-related visuospatial deficit and balance problems.