Clinical Sciences/Health Conditions
Kei Kakegawa, MS
Researcher
Juntendo University
Bunkyo-ku, Tokyo, Japan
Tadamitsu Matsuda, PhD
professor
Department of Physical Therapy, Faculty of Health and Medical Sciences, Juntendo University
Bunkyo-ku, Tokyo, Japan
Junya Ogawa, n/a
Reseacher
PDit
Bunkyo-ku, Tokyo, Japan
yuki Soutome, n/a
Researcher
PDit
Chuou-ku, Tokyo, Japan
Yuji Fujino, PhD
Associate Professor
Juntendo University
Bunkyo-ku, Tokyo, Japan
Postural reflex abnormalities are a characteristic symptom of Parkinson’s disease (PD) and negatively affect quality of life. Impaired subjective vertical perception has been linked to postural instability and may serve as an early predictor of postural decline. However, few studies have simultaneously examined the Index of Postural Stability (IPS) and subjective postural/visual verticality (SPV/SVV). This study aimed to clarify the relationship between subjective vertical deviation, IPS, and postural abnormalities in early-stage PD.
Design:
Four individuals with early-stage PD (Hoehn and Yahr stage 1; 62.3 ± 9.9 years) participated. SPV was measured using a movable seat in an eyes-closed condition, recording the angle perceived as “vertical.” IPS was obtained using a posturography system (ANIMA) during quiet standing and voluntary weight shifts in anteroposterior and mediolateral directions, following the method of Mochiduki et al. Static standing posture was assessed in a relaxed stance.
Results:
SPV assessment showed rightward deviation in three participants and forward deviation in two, with greater anteroposterior than mediolateral displacement. The mean IPS value was 1.1 ± 0.3, lower than typical healthy levels. IPS tended to decrease in the same direction as SPV deviation; forward-deviation cases demonstrated reduced IPS in both anteroposterior directions. Static posture analysis revealed multiple compensatory patterns, including trunk flexion, extension, and lateral bending toward either the same or opposite side of the SPV deviation axis.
Conclusion:
Even in early-stage PD, deviations in perceived verticality and reduced postural stability may already be present. The correspondence between SPV deviation direction and IPS reduction suggests an interaction between sensory misperception of verticality and postural control impairment. These findings indicate potential subtypes based on whether perceptual or postural changes appear first. Further investigation of multisensory integration measures, including SVV, may support the development of simple and clinically feasible early-stage interventions.
