Long-term response to aminopyridines in a cohort of patients with ataxia associated with downbeat nystagmus due to the FGF14 GAA expansion E. Muñoz; M. De la Cruz-Puebla; D. Pellerin; C. Painous; M.I. Álvarez-Mora; M.J. Dicaire; L. Rodríguez-Revenga; M.C. Danzi; S. Zuchner; B. Brais;