In addition to alterations in executive oculomotor functions, C9orf72 carriers showed hypometric horizontal and asymmetric vertical saccades which indicate ‘genuine’ oculomotor dysfunctions, although the change of the horizontal saccade gain is commonly observed in patients with FTD [33] but not in ALS patients [12, 15] and might be regarded as another element of the C9orf72-associated overlap of motor neuron disease and frontotemporal pathology. Here, C9orf72 is linked to motor neuron disorder.