Inclusion Criteria:  aged between 14 and 70 years patients with pure hereditary spastic paraplegias with progressive weakness and spasticity of the lower limbs, and the gait dysfunction treatable by medication but not adequately controlled with medications Understand potential risk/benefit, consent to the study, study procedures, and agree to complete the study follow-up visits and comply with the study protocol requirements.  Exclusion Criteria:  cognitive impairment ( MMSE≤24), depression (HAMD>24),acute psychosis, active alcohol or drug abuse, terminal illness, and any major medical or psychological histories, diagnoses, conditions, or comorbidities that would interfere with participation in the study per the investigatior's medical judgment surgical or medical contraindications to spinal cord stimulation surgery(e.g. uncontrolled hypertension, advanced coronary artery disease).