RecruitingDevice studyNeuromodulation to Enhance Motor Function in HSPHereditary spastic paraplegia (HSP) is a rare neurological condition that causes stiffness, weakness, and difficulty walking due to damage in the nerves that control movement. This study will test whether a noninvasive form of spinal cord stimulation, called transcutaneous spinal cord stimulation (tSCS), can improve walking and reduce muscle stiffness in adults with HSP. In this study, participants will receive tSCS twice a week for 8 weeks. The stimulation is delivered through self-adhesive electrodes placed on the skin over the lower back and does not require surgery. Each session will last about one hour. After the treatment period, participants will be followed for an additional 8 weeks without stimulation to see whether any improvements are maintained. Researchers will measure walking speed, walking endurance, muscle stiffness, and overall disease severity. Additional tests will explore changes in bladder and bowel function and muscle strength.