Application of a Scale for the Assessment and Rating of Ataxia (SARA) in Friedreich's ataxia patients according to posturography is limited
Introduction
Friedreich's ataxia (FRDA) is the most frequently inherited ataxia, affecting about 1 in 30 000 individuals in Western Europe [1]. There is no treatment, although several clinical trials have been conducted in recent years. In FRDA, as in other progressive neurological conditions, accurate and efficient measurement of disease progression is necessary to evaluate the effectiveness of therapy.
Because of the heterogeneous presentation of FRDA and its slow progression it is very difficult to find a reliable instrument for measuring the changes of the FRDA's symptoms over time. The Friedreich's ataxia rating scale (FARS) [2], International Cooperative Ataxia Rating Scale (ICARS) [3], and the Scale for the Assessment and Rating of Ataxia (SARA) [4] are the recommended neurological examination-based instruments most used to assess the disease among persons with FRDA and combined forms of ataxia.
The FARS was developed as a disease-specific rating scale for FRDA patients. Initial studies showed that FARS is a more sensitive measure than ICARS [5] and has been used in clinical trials in FRDA patients. This scale examines both sensory and cerebellar symptoms [6]. The disadvantage is that it is time consuming.
The SARA, a shorter ataxia scale, was developed to measure symptoms of cerebellar ataxia in autosomal dominant spinocerebellar ataxia (ADCA). Since FRDA also has sensory (afferent) elements of ataxia, SARA was not considered to be appropriate for FRDA and was not evaluated in FRDA patients [7]. A recent study based on a comparison of the three rating scales – ICARS, FARS and SARA – indicated that SARA may be appropriate for clinical trials of FRDA patients [6]. Further, the study showed that SARA measures disease severity and progression in FRDA patients [8].
Posturographic examination has been used for measurement of postural stability and quantitative documentation of postural ataxia [9]. Increased postural instability was observed among cerebellar patients and correlated with balance impairment on a clinical ataxia rating scale [10].
Our study aimed to determine whether posturographic parameters are associated with balance impairment assessed by specified clinical ataxia rating scales among FRDA (SARA, FARS) and ADCA (SARA) patients.
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Patients
Thirteen spinocerebellar ataxia type 2 (SCA2) patients for which the threshold number of CAG repeats in ATXN2 gene was 33 [11], [12] and 11 FRDA patients, all homozygotes for expanded GAA repeat in the FRDA gene, genetically confirmed by the Ataxia Center at Motol Hospital in Prague, were assessed by the SARA semi-quantitative clinical rating scale. Patients with FRDA in addition were assessed by FARS. All assessments were performed at the same time and by the same neurologist specializing in
Results
Demographic data and clinical rating scale scores are presented in Table 1. All defined postural stability parameters correlated with balance impairment on SARA and FARS among FRDA patients in stance with visual control. Total SARA and FARS scores correlated with postural stability parameters in stance with visual control. In stance without visual control, balance impairment and total score on SARA did not correlate with defined postural stability parameters, unlike FARS, where balance
Discussion
The SARA was developed to measure symptoms of cerebellar ataxia in ADCA and was not initially recommended for FRDA. In ADCA, unlike FRDA, the isolated cerebellar dysfunction causes ataxia [5]. Recent studies indicated that SARA may be appropriate for use in clinical trials among FRDA patients [6], [8]. This assumption was also supported by our results in stance with visual control in which correlations between all posturography parameters and SARA total score/SARA posture were significant.
Conclusion
We investigated the association between posturographic parameters and clinical rating scales SARA and FARS in FRDA patients. Our results showed that in stance with visual control, balance impairment on SARA and FARS was related to all posturographic parameters, but in stance without visual control, none of them was associated with SARA but all were associated with FARS.
The results suggested that SARA may be appropriate in assessing patients with FRDA, but still FARS may have some advantages
Conflict of interest
The authors have no conflicts of interest relevant to this article to disclose.
Acknowledgment
We would like to thank the patients who participated in this study and their families. This study was supported by MH CZ—DRO, University Hospital Motol, Prague, Czech Republic 00064203; MSM 0021620864; GACR P407/11/P784; PRVOUK P38; the European Regional Development Fund—Project FNUSA-ICRC (No. CZ.1.05/1.1.00/02.0123) and by project ICRC-ERA-HumanBridge (no. 316345). Institutional Support of Laboratory Research Grant No. 2/2012 (699002).
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