SPAST and hereditary spastic paraplegia: Originally, SPG4-linked HSP had been considered as a pure form (in which only a pyramidal syndrome is found), however, later studies reported that patients with SPG4-HSP also exhibit cognitive impairment (Orlacchio et al., 2004; Murphy et al., 2009; Chelban et al., 2017; Akaba et al., 2021; Erfanian Omidvar et al., 2021; Giordani et al., 2021).