Assessing Postural Rigidity from Quiet Stance in Patients with Parkinson’s Disease.


Carson Chow, Ph.D.
Department of Mathematics
University of Pittsburgh School of Medicine


Currently, the severity and extent of Parkinson’s disease (PD) is measured with clinical rating scales that rely on the examiner’s interpretation of clinical findings. An entirely objective quantitative assessment measure would be highly useful. Recently, such a measure for postural stiffness was developed. This measure can be determined by having a patient stand on a piece of equipment called a “biomechanical force platform.” The basic measurement is called a center-of-pressure (COP) trajectory.

Previous work which Dr. Chow was involved has shown correlations of the postural stiffness measure with different clinical rating scales, obtained from patients with PD. From a clinical standpoint, this work indicates that the proposed postural stiffness measure may be useful as an assessment tool for the evaluation of PD patients subsequent to pharmacological and surgical treatment. Dr. Chow and his associates propose to do a more detailed statistical analysis of the data to evaluate the reliability and robustness of the postural stiffness measure and to evaluate other measures that can be mathematically modeled from the data obtained during each testing session. Their goals are to (1) understand the within patient variations in the statistics of the measures extracted from the COP trajectories, (2) analyze how these measures are affected by various drugs and therapies to which the patient is exposed, and (3) study the association of the mathematically derived measures and clinical measures that are relevant to a patient’s quality of life, such as propensity to falling, inability to turn over in bed, and positional wooziness or dizziness. Dr. Chow’s group plans to study up to 160 patients with PD and other types of Parkinsonism or gait disorders and 40 normal volunteers over a period of 1-2 years. They will use a Kistler portable biomechanics force plate system in this testing.

Progress Report (as of 8/2002)

The primary purpose of the grant was the acquisition of a Kistler force platform to test balance impairment in Parkinsonian patients, first degree relatives of such patients, and normal controls. The platform is installed and functions in the Neurology Clinic on the 10th floor at the VA Hospital. The data acquisition takes place under a specific, well defined protocol. So far we tested 35 Parkinsonian, 6 first degree relatives of parkinsonians, and about 20 normal controls. We continue to collect data. Initial results were presented in the paper “Developing measures of postural rigidity from quiet stance on an electronic platform.” The results of the paper were presented by one of the authors, in the form of an invited paper, at the International Meetings of the International Statistical Institute in Seoul, South Korea, in August 2001. The paper is published in the Bulletin of the International Statistical Institute. A more comprehensive paper entitled “Stiffness measures and first crossing times in Parkinsonians and normal controls” is in progress. A paper that incorporates available information on first degree relatives in Parkinsonians, tentatively entitled “Electric platform measures of balance impairment in Parkinsonians and first degree relatives” is in progress. A National Institute of Health comprehensive grant proposal entitled “Pet Posturographic and Clinical Markers of Early PD, with Dr. Zigmond as Principal Investigator, is now being evaluated.

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