Longitudinal changes occurring over time in the brains of HSP patients are still unclear: for example, disease progression seems to differ between the various HSP forms because little or no progression is described in some (SPG3), while a clear worsening is documented in others (SPG4) even within a few years (Schneider-Gold et al., 2017). The gene discussed is ATL1; the disease is hereditary spastic paraplegia.