Gait disorders and balance disturbances in Parkinson's disease: Clinical update and pathophsyiology (online?)

Purpose of review: Gait disorders and balance impairments are one of the most incapacitating symptoms of Parkinson's disease. Here, we discuss the latest findings regarding epidemiology, assessment, pathophysiology and treatment of gait and balance impairments in Parkinson's disease. Recent findings: Recent studies have confirmed the high rate and high risk of falls of patients with Parkinson's disease. Therefore, it is crucial to detect patients who are at risk of falling and how to prevent falls. Several studies have shown that multiple balance tests improve the prediction of falls in Parkinson's disease. Difficulty turning may be caused by axial rigidity, affected interlimb coordination and asymmetries. Turning difficulties are easily assessed by timed performance and the number of steps during a turn. Impaired sensorimotor integration, inability of switching between sensory modalities and lack of compensatory stepping may all contribute to the high incidence of falls in patients with Parkinson's disease. Similarly, various studies highlighted that pharmacotherapy, neurosurgery and physiotherapy may adversely affect balance and gait in Parkinson's disease. Summary: Insights into the pathophysiology of Parkinson's disease continue to grow. At the same time, it is becoming clear that some patients may in fact deteriorate with treatment. Future research should focus on the development and evaluation of multifactorial fall prevention strategies

The clinical utility of posturography

Postural instability and falls are common and devastating features of ageing and many neurological, visual, vestibular or orthopedic disorders. Current management of these problems is hampered by the subjective and variable nature of the available clinical balance measures. In this narrative review, we discuss the clinical utility of posturography as a more objective and quantitative measure of balance and postural instability, focusing on several areas where clinicians presently experience the greatest difficulties in managing their patients: (a) to make an appropriate differential diagnosis in patients presenting with falls or balance impairment; (b) to reliably identify those subjects who are at risk of falling; (c) to objectively and quantitatively document the outcome of therapeutic interventions; and (d) to gain a better pathophysiological understanding of postural instability and falls, as a basis for the development of improved treatment strategies to prevent falling. In each of these fields, posturography offers several theoretical advantages and, when applied correctly, provides a useful tool to gain a better understanding of pathophysiological mechanisms in patients with balance disorders, at the group level. However, based on the available evidence, none of the existing techniques is currently able to significantly influence the clinical decision making in individual patients. We critically review the shortcomings of posturography as it is presently used, and conclude with several recommendations for future research

Bonding and Reactivity in Terminal versus Bridging Arenide Complexes of Thorium Acting as Th II Synthons

International audienceThorium redox chemistry is extremely scarce due to the high stability of Th-IV. Here we report two unique examples of thorium arenide complexes prepared by reduction of a Th-IV-siloxide complex in presence of naphthalene, the mononuclear arenide complex [K(OSi((OBu)-Bu-t)(3))(3)Th(eta(6)-C10H8)] (1) and the inverse-sandwich complex [K(OSi((OBu)-Bu-t)(3))(3)Th](2)(mu-eta(6),eta(6)-C10H8)] (2). The electrons stored in these complexes allow the reduction of a broad range of substrates (N2O, AdN(3), CO2, HBBN). Higher reactivity was found for the complex 1 which reacts with the diazoolefin IDipp=CN2 to yield the unexpected Th-IV amidoalkynyl complex 5 via a terminal N-heterocyclic vinylidene intermediate. This work showed that arenides can act as convenient redox-active ligands for implementing thorium-ligand cooperative multielectron transfer and that the reactivity can be tuned by the arenide binding mode

Participant characteristics.

<p>Data reflect means (standard deviation between brackets). N; number of subjects, NS; not significant, UPDRS; Unified Parkinson’s Disease Rating Scale, L: Left side most affected H&Y Hoehn & Yahr, FAB; Frontal Assessment Battery. NFoG-Q; new freezing of gait questionnaire.</p>†<p>Mann-Whitney U test.</p><p>Patients were assessed during the OFF state. There were no significant differences between patients and controls, or between freezers and non-freezers.</p

Experimental set-up.

<p>Participants stood on the dual forceplate (A), with their arms crossed over their chest, embedded in the movable platform (B). Two independent perturbations in the forward-backward direction were applied simultaneously using both the movable platform (B) and the pusher (C). Interaction forces between the pusher (C) and the participant were measured with a force sensor (D). Actual falls were prevented by the safety harness (E), which did not provide any support or directional cues. Reflective spherical markers (F) measured movements of the participant.</p

Comparison of clinical outcome measures between patients with (ASYM) and without (SYM) asymmetrical weight bearing or asymmetric balance control, based on the 99 percent CI of weight bearing, the ankle joint or the hip joint contributions of the healthy controls.

<p>Data reflect means with the standard deviation (between brackets). N, number of subjects, UPDRS Unified Parkinson’s Disease Rating Scale; H&Y Hoehn & Yahr; PIGD; Postural Instability and Gait Difficulty; TMT; Ten Meter walk Test, TUG; Timed-Up-and-go-Test; ASYM = asymmetrical patients. SYM = symmetrical patients.</p><p>Due the small sample we used non-parametric tests (Mann Whitney U test) or χ2 tests indicated with (∼).</p><p><i>p</i> values are not corrected for multiple comparisons, but the significance level reduced 0.005 due to Bonferoni correction.</p><p>There were no significant differences in clinical outcome measures between patients with and without asymmetrical weight bearing or balance control.</p

Timeseries and powerspectrum of the two perturbation signals.

<p>The left panels represent the platform perturbation; the right panels the pusher perturbation.</p

Clinical asymmetry, weight-bearing and balance-control contribution of the left (lower bar) and right leg (upper bar) of the individual PD patients.

<p>The absolute and relative value and the most affected side of the clinical asymmetry is shown above the bar graphs. The upper panel indicates the dynamical weight bearing (DWB), the middle panel the dynamic-balance contribution of the ankle joint (DBC_Ank), and the lower panel is of the hip joint (DBC_Hip). The group is separated in non-freezers (the first 11 patients, indicated by the solid bars) and freezers (patient 12 through 20, indicated by the dashed bars). There were no significant differences in asymmetry of WB, DBC_Ank nor DBC_Hip between non-freezers and freezers. The dashed line indicate the 99-percent confidence intervals of the healthy controls for the WB, DBC_Ank, and DBC_Hip. The asterisk (*) denotes balance contributions outside the respective confidence intervals. For WB, 14 patients were outside the 99 percent CI. This number increased to 15 considering DBC_Ank and to 16 for DBC_Hip. ns = not significant. The clinically most affected side coincided in most cases with weight-bearing and balance-control asymmetry. However, there were no significant correlations between clinical asymmetry and balance asymmetry (WB, p = 0.32; DBC_Ank, p = 0.37 and DBC_Hip, p = 0.75).</p