Spinal cord damage in Friedreich’s ataxia: Results from the ENIGMA-Ataxia

ObjectiveSpinal cord damage is a hallmark of Friedreich ataxia (FRDA), but its progression and clinical correlates remain unclear. Here we performed a characterization of cervical spinal cord structural abnormalities in a large multisite FRDA cohort.MethodsWe performed a cross-sectional analysis of cervical spinal cord (C1 to C4) cross-sectional area (CSA) and eccentricity using MRI data from eight sites within the ENIGMA-Ataxia initiative, including 256 individuals with FRDA and 223 age- and sex-matched controls. Correlations and subgroup analyses within the FRDA cohort were undertaken based on disease duration, ataxia severity, and onset age.ResultsIndividuals with FRDA, relative to controls, had significantly reduced CSA at all examined levels, with large effect sizes (d>2.1) and significant correlations with disease severity (rd>1.2), but without significant clinical correlations. Subgroup analyses showed that CSA and eccentricity are abnormal at all disease stages. However, while CSA appears to decrease progressively, eccentricity remains stable over time.InterpretationPrevious research has shown that increased eccentricity reflects dorsal column (DC) damage, while decreased CSA reflects either DC or corticospinal tract (CST) damage or both. Hence, our data support the hypothesis that damage to DC and CST follow distinct courses in FRDA: developmental abnormalities likely define the DC, whereas CST alterations may be both developmental and degenerative. These results provide new insights about FRDA pathogenesis and indicate that CSA of the cervical spinal cord should be investigated further as a potential biomarker of disease progression.