C9orf72 and amyotrophic lateral sclerosis: One of the best characterised ALS cohorts is patients carting the GGGGCC hexanucleotide repeat expansion in C9orf72, a genotype that is typically linked to extensive extra-motor, subcortical, thalamic and cerebellar manifestations [25,27,322] and pre-symptomatic thalamic changes [28,323].