Superior cerebellar peduncle atrophy in Friedreich's ataxia correlates with disease symptoms.

Friedreich's ataxia (FRDA) is the most common early onset inherited ataxia with clinical manifestations, including gradual progression of unremitting cerebellar-sensory ataxia, peripheral sensory loss, loss of lower limb tendon reflexes and hypertrophic cardiomyopathy. Although atrophy of the superior cerebellar peduncle (SCP) has been reported in several magnetic resonance imaging (MRI) studies of FRDA, the relationship of SCP changes to genetic and clinical features of FRDA has not been investigated. We acquired T1-weighted MRI scans in 12 right-handed individuals with FRDA, homozygous for a GAA expansion in intron 1 of FXN, as well as 13 healthy age-matched controls. The corrected cross-sectional areas of the right (left) SCP in the individuals with FRDA (R, 20 ± 7.9 mm(2); L, 25 ± 5.6 mm(2)) were significantly smaller than for controls (R, 68 ± 16 mm(2); L, 78 ± 17 mm(2)) (p < 0.001). The SCP volumes of individuals with FRDA were negatively correlated with Friedreich's ataxia rating scale score (r = -0.553) and disease duration (r = -0.541), and positively correlated with the age of onset (r = 0.548) (p < 0.05). These findings suggest that structural MR imaging of the SCP can provide a surrogate marker of disease severity in FRDA and support the potential role of structural MRI as a biomarker in the evaluation of neurodegenerative diseases and therapies.