Objective: Biomechanical assessment of postural imbalance in patients with Progressive Supranuclear Palsy (PSP)

Background: PSP is a neurodegenerative disease characterized by early impairment of balance and frequent falls. Biomechanical features underlying postural imbalance in these patients are largely unknown.

Method: We recruited 21 patients with PSP (8M; age: 67.4±5.1ys; disease duration: 5.4±2.7ys) and 12 age- and gender-matched healthy controls (HC) (7M; age: 65.1±3.7ys). Posturography was performed with two dynamometric platforms (Kistler). We recorded three trials (30s each) of quite standing with eyes open and arms down by the side of the body. The PSP Rating Scales (PSPRS) was calculated at the time of examination. We used ad hoc Matlab algorithms to describe all conventional posturography measurements (e.g. antero-posterior [AP] and medio-lateral [ML] excursion and velocity of the Centre of Pressure [CoP]). We also calculated the percentage of observation of CoP displacement falling at boundaries of CoP displacement (Extreme 40% observation of AP and ML CoP displacement [E40AP and E40ML]) as a possible index of risk of falling in PSP. We computed only measurements not influenced by anthropometric parameters and base of support.

Results: The area of the ellipse (cm2) described by the CoP as well as the mean distance (mm) and root mean square (mm) significantly differed between HC and PSP patients (HC: 95.4±53.4, 4.1±1.3, 4.8±1.5, and PSP: 185.9±107.1, 6.7±2.3, 7.9±2.7, Wilcoxon p<0.05 all) and correlated with the “PSPRS Limb motor” subscore (Spearman’s ρ 0.51, 0.53 and 0.56 respectively). Both E40AP and E40ML measurements also differed between the two cohorts (HC: 17.5±3.2%, 17.3±4.1% and PSP 24.0±5.1%, 21.9±6.6%, Wilcoxon p<0.05 all) and correlated with “PSPRS gait and midline” subscore (Spearman’s ρ 0.52 and 0.65, respectively).

Conclusion: Postural control was severely impaired in PSP patients as shown by larger CoP displacement with respect to HC. The rigidity and bradykinesia prevented patients to counteract promptly perturbations of the Centre of Mass and efficiently control balance. The inability to modulate motor transitions was correlated to a longer permanence of the CoP at the boundaries of its excursion, reflecting poor control of CoP position. This measurement could be of use to monitor (sub-)clinical changes in prospective interventional studies.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/postural-alterations-in-patients-with-progressive-supranuclear-palsy/