Subjective postural vertical in Parkinson's disease with lateral trunk flexion

Sex-related differences in the posture and vertical perception of gait function in patients with Parkinson's disease

BACKGROUND

Although several factors, such as sex and body schema, contribute to gait function, factors for gait dysfunction in Parkinson's disease (PD) have not been elucidated. Postural verticality, a higher-order neural mechanism of gait, is involved in generation of a gait program in healthy individuals; however, its role in patients with PD is unclear. Although subjective postural vertical (SPV), which denotes cognitive information about posture with verticality as the reference axis, is anteriorly and laterally shifted in patients with PD, the presence of sex-related differences in SPV and effect of SPV on gait function remain unclear. Since SPV affects the degree of flexion and lateral bending posture and long-term prognosis of PD, factors affecting SPV in patients with PD should be clarified to improve gait function.

RESEARCH QUESTION

Is vertical perception of posture (i.e., SPV) related to gait function in patients with PD? Are there any sex-related differences?

METHODS

The gait and SPV were evaluated in 59 adult outpatients with PD (31 men and 28 women) using five gait (step length, walking speed, coefficient of variation of step time [step CV], cadence, and mean gait acceleration [acceleration]) and two SPV (SPV in the sagittal and coronal planes) assessments and compared between the sexes.

RESULTS

No sex-related differences were observed in the SPV in patients with PD. The SPV and gait assessments demonstrated no association in men. Walking speed and SPV in the sagittal plane (p = 0.029), and step CV and SPV in the coronal (p = 0.018) and sagittal planes (p = 0.032) were correlated in women.

SIGNIFICANCE

Although no sex-related differences in the SPV were observed, our results demonstrated that the SPV is involved in gait function in women but not in men with PD.

Predictors and Pathophysiology of Axial Postural Abnormalities in Parkinsonism: A Scoping Review

Background

Postural abnormalities involving the trunk are referred to as axial postural abnormalities and can be observed in over 20% of patients with Parkinson's disease (PD) and in atypical parkinsonism. These symptoms are highly disabling and frequently associated with back pain and a worse quality of life in PD. Despite their frequency, little is known about the pathophysiology of these symptoms and scant data are reported about their clinical predictors, making it difficult to prompt prevention strategies.

Objectives

We conducted a scoping literature review of clinical predictors and pathophysiology of axial postural abnormalities in patients with parkinsonism to identify key concepts, theories and evidence on this topic.

Methods

We applied a systematic approach to identify studies, appraise quality of evidence, summarize main findings, and highlight knowledge gaps.

Results

Ninety-two articles were reviewed: 25% reported on clinical predictors and 75% on pathophysiology. Most studies identified advanced disease stage and greater motor symptoms severity as independent clinical predictors in both PD and multiple system atrophy. Discrepant pathophysiology data suggested different potential central and peripheral pathogenic mechanisms.

Conclusions

The recognition of clinical predictors and pathophysiology of axial postural abnormalities in parkinsonism is far from being elucidated due to literature bias, encompassing different inclusion criteria and measurement tools and heterogeneity of patient samples. Most studies identified advanced disease stage and higher burden of motor symptoms as possible clinical predictors. Pathophysiology data point toward many different (possibly non-mutually exclusive) mechanisms, including dystonia, rigidity, proprioceptive and vestibular impairment, and higher cognitive deficits.

Effect of subjective vertical perception on lateral flexion posture of patients with Parkinson's disease

In a retrospective study we tested our hypothesis that the subjective postural vertical ratio (SPV ratio), i.e., the subjective postural vertical measured in relation to the lateral flexion axis, is predictive of lateral trunk flexion in patients with Parkinson's disease (PD). Twenty-five patients were included. The SPV angle, i.e., the subjective perception of a vertical position with reference to the vertical axis, and the SPV ratio, i.e., the SPV angle with reference to the axis of lateral flexion, were calculated. The SPV ratio (r = 0.698, P = 0.001) and LTF angle (r =  - 0.601, P = 0.001) correlated with change in the LTF angle at 1 year. The SPV ratio was significantly smaller in patients for whom lateral trunk flexion improved (n = 12) than in those for whom it did not improve (n = 13) (0.99 ± 0.78 vs 1.66 ± 0.71, P = 0.011). The AUC under the ROC curve of the SPV ratio for discrimination of improvement was 0.795 (95% confidence interval: 0.61-0.98). We found that the SPV ratio is associated with change in the LTF and that it can conceivably be used to predict the likelihood of improvement in PD-associated lateral trunk flexion.

Contribution of Basal Ganglia to the Sense of Upright: A Double-Blind Within-Person Randomized Trial of Subthalamic Stimulation in Parkinson's Disease with Pisa Syndrome

BACKGROUND

Verticality perception is frequently altered in Parkinson's disease (PD) with Pisa syndrome (PS). Is it the cause or the consequence of the PS?

OBJECTIVE

We tested the hypothesis that both scenarios coexist.

METHODS

We performed a double-blind within-person randomized trial (NCT02704910) in 18 individuals (median age 63.5 years) with PD evolving for a median of 17.5 years and PS for 2.5 years and treated with bilateral stimulation of the subthalamus nuclei (STN-DBS) for 6.5 years. We analyzed whether head and trunk orientations were congruent with the visual (VV) and postural (PV) vertical, and whether switching on one or both sides of the STN-DBS could modulate trunk orientation via verticality representation.

RESULTS

The tilted verticality perception could explain the PS in 6/18 (33%) patients, overall in three right-handers (17%) who showed net and congruent leftward trunk and PV tilts. Two of the 18 (11%) had an outstanding clinical picture associating leftward: predominant parkinsonian symptoms, whole-body tilt (head -11°, trunk -8°) and transmodal tilt in verticality perception (PV -10°, VV -8.9°). Trunk orientation or VV were not modulated by STN-DBS, whereas PV tilts were attenuated by unilateral or bilateral stimulations if it was applied on the opposite STN.

CONCLUSION

In most cases of PS, verticality perception is altered by the body deformity. In some cases, PS seems secondary to a biased internal model of verticality, and DBS on the side of the most denervated STN attenuated PV tilts with a quasi-immediate effect. This is an interesting track for further clinical studies.