All authors contributed equally to this work. Susana Arias-Rivas wrote the main paper. Manuel Rodriguez-Yáñez investigated the supplementary data. Julia Cortés and Pablo Aguiar performed the nuclear image studies and analysed and described the neuroimaging results. María Pardo, Rogelio Leira and Jose Castillo jointly conceived the study, followed the patient and prepared the manuscript. Miguel Blanco discussed the results. All authors discussed the results and implications and commented on the manuscript at all stages.