1. Department of Neurosurgery, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA;
2. Department of Neurosurgery, The Neurological Institute, University Hospital Cleveland Medical Center, Cleveland, Ohio, USA;
3. Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA;
4. Louis Stokes Cleveland Department of Veterans Affairs Medical Center, FES Center of Excellence, Rehab. R&D Service, Cleveland, Ohio, USA