Analysis of the subjective postural vertical on diagonal plane in elderly subjects and left hemiparetic patients after stroke

Introduction/Background The subjective postural vertical (SPV) in healthy subjects is robustly maintained by integrating somatosensory and vestibular information, and extremely correct on frontal and sagittal plane. It is well-known that brain injury patients indicate disturbance of SPV on frontal or sagittal plane. On the other hand, stroke patients frequently fall paretic side and backward, but SPV on diagonal plane in normal subjects and stroke patients is unclear. The purpose of present study was to clarify the difference of SPV on diagonal plane between elderly subjects and stroke patients. Material and method The subjects comprised 14 elderly subjects (control group) and 10 left hemiparetic patients (LHP group). All subjects provided their written informed consent to take part in the study. SPV was measured using an electrical vertical board (EVB). The subjects sat on the EVB and were moved in the opposite direction from the left-backward or right-forward. The tilt of the seat when the subject feels and judges vertical position was recorded with a digital inclinometer. The mean (tilt direction) and standard deviation (variability) of eight trials were calculated. A true vertical position was considered 0°, diagonally backward and diagonally forward was treated as negative and positive, respectively. The values of SPV were compared between groups using the unpaired t-test ( P Results There was no difference between control group (66.8 ± 9.2 years [mean ± SD]) and LHP groups (67.5 ± 10.8 years) in age. In tilt direction, LHP group (−2.5 ± 0.7°) demonstrated significant tilt backward to the left than control group (−1.3 ± 1.4°). Variability was significantly higher in LHP (5.4 ± 2.0°) than control (2.5 ± 0.9°). Conclusion In stroke patients, tilt direction deviated to the diagonally backward and the judgement of verticality was unstable. These results suggest a possibility to explain the tilt of sitting posture and the difficulty of transfer movement in stroke patients.