Twenty-five studies were included (n=540, range three to 87): 10 randomised controlled trials (RCTs) (n=220); one non randomised controlled trial (n=56); and 14 case series (n= 264). Jadad scores were 1 for one RCT, 3 for three RCTs, 4 for six RCTs and 5 for one RCT. Loss to follow-up ranged from 0 to 26.9%. No RCTs conducted intention-to treat analysis.
Follow-up ranged from 3.5 to 48 months; it was 12 months in most studies.
There was some evidence that 5-hydroxytryptophan was more effective than placebo in the improvement of neurological symptoms in patients with Friedreich's ataxia, olivopontocerebellar atrophy or cerebellar atrophy. Positive effects were reported in two of three RCTs and two case series reported positive effects.
Idebenone was found to be more effective than placebo for reducing mean thickness of some but not all cardiac dimensions in patients with the hypertrophic cardiomyopathy associated with Friedreich's ataxia, but patient response was highly variable (one RCT). Three case series reported reductions in some but not all cardiac dimensions. One of two case series reported a reduction in cardiac hypertrophy. Findings for changes in neurological impairment were mixed (one RCT and two case series). Three case series reported improvements in some measures of functional capacity from baseline.
There was limited evidence for other therapies.