Stance instability in preclinical SCA1 mutation carriers: A 4-year prospective posturography study.

OBJECTIVE

We aimed to study postural balance in preclinical Spinocerebellar ataxia type 1 (SCA1) mutation carriers to identify and observe specific motor functional deficit before evident clinical manifestation.

METHODS

Participants were 9 asymptomatic SCA1 mutation carriers (6M/3F), aged 31.8±7years (range 22-44), and 17 age-matched non-carrier controls (5M/12F) (age 18-42). Subjects underwent postural tests on a force platform (Tetrax-IBS, Sunlight Medical Ltd.) with and without visual feedback. Amount of body sway was represented by stability index (ST). Tests were repeated after 2- and 4-years. Estimated years to onset were calculated.

RESULTS

In controls, ST was unchanged from baseline to 4-year evaluations in all standing conditions. SCA1 mutation carriers performed similarly to controls in the postural tasks with open eyes, whereas in conditions without visual feedback SCA1 carriers had significantly higher ST than controls at all longitudinal evaluations. Close-to-disease onset carriers (≤7years) showed more prominent time-dependent stance abnormalities (p<0.0001 for all comparisons).

CONCLUSIONS

Traceable and progressive postural abnormalities can be observed in preclinical close-to-onset SCA1 carriers. Quantitative analysis of stance could represent a promising outcome measure in clinical trials including preclinical subjects.