Different postural reaction patterns for expected and unexpected perturbations in patients with idiopathic Parkinson's disease and other parkinsoniansyndromes

Different postural reaction patterns after predictable and unpredictable pe rturbations during free stance were studied in 8 patients with idiopathic P arkinson's disease (iPD), in 4 patients with other parkinsonian syndromes ( PS) and in 5 healthy controls. First, the amplitude of leaning maximally ba ckward and forward was measured (condition I). Secondly, the body equilibri um was disturbed by self-paced, predictable, rapid arm elevations (conditio n II) and by sudden unpredictable toe-down and toe-up rotations of a suppor ting platform (condition III). Patients with PS particularly had difficulti es in regaining body equilibrium after unexpected perturbations, In control s and patients with PS, unpredictable disturbances were better compensated in toe-down than in toe-up direction, whereas the opposite was true for pat ients with iPD, These results correspond to the fact that patients,vith PS had a specific leaning-backward impairment and patients with iPD, a leaning -forward impairment. The authors conclude that the differences in postural stability between patients with iPD and PS are caused by different pathophy siological mechanisms. These differences in postural stability could serve as an additional tool for differential diagnosis. fur J Neurol 6:549-554 (C ) 1999 Lippincott Williams & Wilkins.