Research Article: Forward flexion of trunk in Parkinson’s disease patients is affected by subjective vertical position

Date Published: July 10, 2017

Publisher: Public Library of Science

Author(s): Kyohei Mikami, Makoto Shiraishi, Tsubasa Kawasaki, Tsutomu Kamo, Manabu Sakakibara.


No method has been established to evaluate the dissociation between subjective and objective vertical positions with respect to the self-awareness of postural deformity in patients with Parkinson’s disease (PD). The purpose of this study was to demonstrate, from the relationship between an assessment of the dissociation of subjective and objective vertical positions of PD patients and an assessment based on established PD clinical evaluation scales, that the dissociation regarding vertical position is a factor in the severity of the forward flexion of trunk (FFT).

Subjects were 39 PD patients and 15 age-matched healthy individuals (control group). Posture was evaluated with measurement of FFT angle during static standing and the subjective vertical position (SV) of the patient. For evaluation of motor function, the Modified Hoehn & Yahr scale, Unified Parkinson’s Disease Rating Scale (UPDRS), 3-m Timed Up and Go Test (TUG), and Functional Reach Test (FRT) were used.

In PD patients, FFT angle in the 3rd tertile of patients was 13.8±9.7°, significantly greater than those in the control group and the 1st and 2nd tertiles of PD patients (control group vs 3rd tertile, p = 0.008; 1st tertile vs 3rd tertile, p<0.001; 2nd vs 3rd tertile, p = 0.008). In multiple regression analysis for factors in the FFT angle, significant factors were SV, disease duration, and the standard deviation of each SV angle measurement. The dissociation between SV and objective vertical position affects the FFT of PD patients, suggesting an involvement of non-basal ganglia pathologies.

Partial Text

Postural deformities are a common symptom of Parkinson’s disease (PD). A forward flexion of trunk (FFT) that becomes severe due to progression of the condition is intractable, and no treatment has been established [1,2]. Such a posture also represents a critical factor in decreased activities of daily living [3]. Appropriate perception of one’s own posture is reportedly difficult in PD patients who have developed postural deformity [4,5]. Recently there have been reported the issue that the onset of postural deformities in PD patients might be related to frontal lobe dysfunction as Behavioral Assessment of the Dysexecutive Syndrome score was significantly lower in PD patients with severe postural deformities than without it [6]. On the basis of these reports, factors other than extrapyramidal disorder are conjectured to be involved in the mechanism of onset for postural deformities. Furthermore, some factors (i.e., rigidity [7], drug-induced [8], dystonia [9], proprioceptive disintegration [10]) other than extrapyramidal disorder are conjectured to be involved in the mechanism of onset for postural deformities.

Baseline characteristics for the PD group are shown in Table 1. FFT was 10.2±14.7° in the PD group overall. Compared with the 3.9±2.6° in the 15 control patients (mean age, 68.3±3.3 years; 7 men), TFF was significantly larger in the PD group (p = 0.032). The baseline characteristics of FFT tertiles in the PD group are shown in Table 2. No differences in age, disease duration, MMSE, H-Y, UDPRS parts, TUG, FRT, levodopa dosage, or dopamine agonist dosage rate were seen between groups (Table 2). In contrast, compared with the FFT of 3.9±2.6° in the control group, the 1st FFT tertile (-15° to 4°) was significantly lower at -3.1±7.2° (p = 0.045), and the 3rd tertile (13° to 45°) was significantly higher at 27.7±11.6° (p < 0.001) (Fig 2). The finding that the dissociation between subjective vertical position and objective vertical position in PD patients shown in this study was a factor in the severity of the FFT supported our hypothesis.   Source:


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