Effects of Spinal Cord Stimulation on Gait in Patients With Parkinson´s Disease

Spinal cord stimulation (SCS) for Parkinson´s disease (PD) has been studied for a decade but consensus on efficacy is still lacking, with the previous stimulation standard paresthesia inducing threshold hampering adequate subject blinding. Considering that tonic stimulation for pain has been shown to be efficacious for most patients on subthreshold stimulation parameters we hypothesize a similar result with it´s use on PD. The investigators aim to: 1. Produce stronger evidence on SCS efficacy for PD in regards to gait, motor scores and quality of life measures by incorporating subthreshold in a randomized cross over placebo-controlled study with a large sample. 2. Identify predictors of good response to SCS therapy by performing trans spinal magnetic stimulation (TSMS) before SCS implant and correlating the response to SCS to that of the noninvasive TSMS. 3. Better provide biomarkers of SCS therapy through functional magnetic resonance imaging and electroencephalographic mapping.