Objectives:

1. Therapeutic effects of STN DBS on the cardinal symptoms of patients with Parkinson’s disease (PD);
2. Insuffi cient benefi ts of the STN DBS on the axial symptoms of gait diffi culty, loss of balance and swallowing difficulty, which are the major causes of death in PD;
3. Acute and short-term benefi cial effect of LFS (low frequency stimulation) on the freezing of gait and swallowing diffi culty;
4. Long-term benefi cial effect of LFS on these symptoms; and
5. Strengths and limitations of these studies and the clinical application and signifi cance of the LFS.