Quantitative evaluation of balance in patients with spinocerebellar ataxia type 1: a case control study

Quantitative assessment of balance in spinocerebellar ataxia type 1 (SCA1).

Evaluation of balance in degenerative ataxias is often clinical and subject to bias. Quantification of balance is crucial for evaluating the efficacy of therapeutic and rehabilitative interventions.

The subjects were 20 patients (males: 14, females: 6) with genetically positive SCA1 and 20 age and gender matched healthy subjects. Ataxia was rated using the International Cooperative Ataxia Rating Scale (ICARS). Balance was assessed by dynamic posturography (Biodex, USA) which included: (a) 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 (b) the limits of stability (LOS) in all directions. Balance index was considered abnormal if the actual value exceeded the predictive value.

Impaired balance was found in 80% of patients (all indices in 35%, OBI+API in 25%, only OBI in 15%, and OBI+MLI in 5%). Compared to controls, SCA1 patients had significantly higher balance indices and lower LOS scores. Unlike in controls, the mean value of API was significantly higher than MLI in SCA1. LOS was found to the best predictor of balance abnormality. In patients, all balance indices had significant positive correlations with ICARS, static score of ICARS, body weight, severity and duration of illness, but not with the CAG repeat length.

Patients with SCA1 had global impairment of balance, with greater instability in anterior-posterior than medio-lateral directions. Apart from severity and duration of illness, body weight was detriment to maintenance of balance in SCA1. This information may be useful in planning balance rehabilitation in SCA.