PLS generally shows a significantly slower course of the disease (reduced rate of progression). The transition of motor symptoms (spasticity) from the first affected muscle region to other regions of the body is much slower. A slow progression (with a delay of five to ten years until the spasticity spreads to other parts of the body) is not uncommon. However, there is also a high degree of variability in PLS. In very rare constellations, rapid progression of spasticity is also possible. Overall, PLS carries the prognosis of a significantly slower
progression of the disease.