Erratum to: J Neurol (2014) 261:267–276 DOI 10.1007/s00415-013-7115-8

The original version of this article unfortunately contained a mistake. The affiliation of the second author (Giancarlo Comi) is incorrect. The correct affiliation should be:

Department of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy.