Cerebellar grey matter volume predicts cerebellar tDCS efficacy in individuals with Friedreich ataxia.

OBJECTIVE

To determine the impact of cerebellar anatomy on ctDCS efficacy in individuals with Friedreich ataxia (FA).

METHODS

We included 24 FA patients (mean age 31 ± 14 years) and 24 age- and sex-matched healthy controls. Patients underwent a 5-day ctDCS intervention, with cerebellar motor and non-motor symptoms assessed using the Scale for the Assessment and Rating of Ataxia (SARA) and the Cerebellar Cognitive Affective Syndrome Scale (CCAS-S), before and after stimulation. MRI was used to measure cerebellar gray matter volume, superior cerebellar peduncle (SCP) diameter, and skin-to-cerebellum distance. Stepwise linear regression analyses examined predictors of motor and cognitive improvements following ctDCS.

RESULTS

FA patients exhibited significantly reduced cerebellar gray matter volume compared to controls (p = 0.024) after intracranial volume correction, skin-to-cerebellum distance did not differ between groups (p = 0.11). Stepwise linear regression analysis disclosed that the anterior cerebellar gray matter volume was a significant predictor of SARA improvement (β = -0.18, p < 0.001) and the posterior cerebellar gray matter volume of CCAS-S improvement (β = -0.13, p 0.023). Neither SCP diameter nor skin-to-cerebellum distance significantly impacted ctDCS efficacy.

CONCLUSION

Cerebellar gray matter volume is associated to ctDCS-induced symptoms improvements in FA.

SIGNIFICANCE: These findings suggest that cerebellar gray matter volume influences ctDCS responsiveness.