Neuromodulation to Enhance Motor Function in HSP

Inclusion Criteria: * Clinical diagnosis of hereditary spastic paraplegia (genetic confirmation if available). * Stable medications for spasticity and other neurologic symptoms for =4 weeks prior to enrollment. * Able to participate in study visits and assessments with or without assistive devices. * If ambulatory: able to walk at least 10 meters with or without an assistive device. * If wheelchair user: able to perform seated mobility tasks and transfers required for assessments. * Capacity to provide informed consent and follow study procedures, with an ability to communicate and understand instructions in English Exclusion Criteria: * Implanted electronic devices (e.g., pacemaker, deep brain stimulator, intrathecal pumps). * Severe cardiopulmonary disease that would make participation unsafe. * Open skin lesions or severe dermatologic conditions at electrode sites. * Pregnancy or plans to become pregnant during the intervention period. * Diagnosed with Primary Lateral Sclerosis (PLS) or another neurological condition that affects walking, such as stroke, multiple sclerosis (MS), or a recent surgery on legs. * Unable to participate in basic movement or mobility assessments, even with their usual mobility device (such as a wheelchair, walker, or cane). People who use wheelchairs or other mobility aids can participate if they can complete the study's mobility assessments in their usual way. * Cognitive or psychiatric conditions that make it difficult to give informed conse…