Direction specific preserved limits of stability in early progressive supranuclear palsy: a dynamic posturographic study.

OBJECTIVES

To quantitatively detect the nature of balance impairment in patients with progressive supranuclear palsy (PSP) using dynamic posturography.

METHODS

Twenty clinically diagnosed PSP patients (8 women, 12 men; age: 62.1 ± 7.7 years; duration: 2.6 ± 1.3 years) and 20 healthy controls were studied. All subjects were right side dominant. They were evaluated by dynamic posturography (Biodex, USA). The measurements included (i) balance indices: ability to control balance in all directions (overall balance index, OBI), front to back (anterior-posterior index, API) and side-to-side (medio-lateral index, MLI), and (ii) the limits of stability (LOS) in 8 directions: forward (FW), backward (BW), right (RT), left (LT), forward-right (FW-RT), forward-left (FW-LT), backward-right (BW-RT) and backward-left (BW-LT).

RESULTS

Compared to controls, patients showed significantly higher OBI (p<0.001), API (p=0.003) and MLI (p<0.001), implying impaired balance. The total LOS score was significantly lower (implying poor stability) in PSP than in controls (18.3 ± 7.3 vs. 28.4 ± 8.5, p<0.001). Patients took significantly longer time to complete LOS test (262.7 ± 33.0 s vs. 135.4 ± 20.6 s, p<0.001). Direction-wise analysis showed that PSP patients had significantly lower LOS scores in FW, BW, RT, FW-RT, BW-RT and BW-LT directions compared to controls. However the scores in LT and FW-LT did not differ significantly.

CONCLUSIONS

PSP patients showed impaired balance indices and decreased overall LOS compared to controls. Though LOS is affected in PSP, the scores in the left (non-dominant side) and forward-left (non-dominant forward diagonal) directions were preserved.