SPAST and hereditary spastic paraplegia: SPAST point mutations and exonic rearrangements have been implicated in 10–40 % of the HSP patients (Hazan et al. 1999; Meijer et al. 2002; Beetz et al. 2006; Loureiro et al. 2013) and in up to 12 % of sporadic forms (Depienne et al. 2006).