Gait disorders in Parkinson's disease - Clinical evaluation and analysis of posture, initiation and stabilized gait

A well informed description: The parkinsonian posture is generally describe d as a stooped one. At the beginning of the disease, the gait troubles rema in moderate; gradually the gait is composed of small steps without a wide b ase; the patient tends to run after his centre of gravity by accelerating t he step (festination phenomenon). Difficulties occurs for starting up (dela y of gait initiation), for about-turn or for clearing obstacles. Kinetic ja mmings and standing around (freezing) can last several seconds and be respo nsible for falls. Postural instability, a major symptom in Parkinson's disease: This symptom is little improved by therapies and is responsible for serious disability, Postural instability induces a disequilibrium and is partially due to a sim ultaneous antagonist muscles contraction and to the impossibility of modify ing postural responses to changing support conditions. The passive viscoela stic properties of muscles and tendons constitute a first line of defence a gainst the disequilibrium and contribute to postural stability in the case of medium disturbances. Automatic and voluntary postural responses which co me into play in the case of major disturbances can also be impaired (delay or defect of the responses). Gait initiation failure are frequent: They result from an increase of the p ostural phase and a decrease of the propulsion forces, depending on a defic it of the postural anticipation mechanisms and also the sequential organiza tion and the integration of two different motor programs, postural and loco motor. They can be controlled partially with sensory stimuli, notably visua l inputs. Data concerning stabilized walking and its pathophysiology remains to be cl arified: Spatial and temporal parameters are impaired: speed, step length a nd swing phase are reduced, while cadence increases to compensate these tro ubles. These modifications are the consequence of an incapacity to produce internal marks to generate regular steps. When the parkinsonian patient is supplied with external marks, these parameters can be normalized. from a pa thophysiological point of view, gait disorders could result from defective central integration of proprioceptive information during movement within th e basal ganglia, associated with a visual perceptive deficit linked with a retinal dopaminergic cells dysfunction and finally from an impairment of th e proprioceptive feedback of the load receptor; in the leg extensor muscles .