Objective: To define the brain metabolic abnormalities related to gait initiation (GI) failure in subjects with Progressive Supranuclear Palsy (PSP).

Background: PSP is an atypical parkinsonian syndrome characterized by early postural instability, axial rigidity, gait disturbance, ocular motor dysfunction and cognitive impairment. Falls are among the most relevant prognostic factors in subjects with PSP. The balance control system of these patients is notably challenged during GI, which exposes them to a greater risk of falling.

Method: We performed a biomechanical evaluation of GI trials in 11 PSP patients (6 males; age: 66.7 ± 7.6 years; disease duration: 4.6 ± 2.3 years; Progressive Supranuclear Palsy Rating Scale score: 33.0 ± 9.7). Subjects were monitored with an optoelectronic system (SMART, BTS) and two dynamometric force plates (9286A, Kistler). Patients were instructed to stand still for 30 seconds on the force plates and to start walking at their self-selected speed after a verbal cue. Each patient repeated the task at least three times. We analysed the key features of the Centre of Pressure and Centre of Mass trajectories during the main phases of GI (imbalance, unloading and stepping phase) by means of ad hoc Matlab algorithms. Results were averaged across trials. All patients also underwent a positron emission tomography with 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (FDG-PET). We then correlated the biomechanical and brain metabolic measurements with the Spearman’s rho coefficient.

Results: In PSP patients, the glucose uptake of the caudate nucleus significantly correlated with most of the biomechanical measurements evaluated. Instead, the metabolic activity of the middle cingulate cortex and medial thalamus specifically correlated with parameters of the imbalance and stepping phase, respectively.

Conclusion: We showed a significant contribution of the caudate nucleus in postural maintenance during the whole GI task in PSP patients. The middle cingulate cortex and medial thalamus may influence the feed-forward motor control and step production, respectively. Our findings are of major interest to unveil the pathophysiological alterations underlying postural instability in PSP patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/gait-initiation-in-patients-with-progressive-supranuclear-palsy-a-biomechanical-and-fdg-pet-study/