Fig. 1

Four-phase flow diagram of the literature selection process according to PRISMA guidelines. From 884, finally 87 studies were selected, of which 71 were identified as clinical trials according to the Clinical Trial definition proposed by the National Institutes of Health (NIH) [35] (see Additional file 1). The 87 studies were grouped in three categories according to the pathology treated in the study: Spinal Cord injury (\(\hbox {n}=54\)), stroke (\(\hbox {n}=22\)) and other pathologies (\(\hbox {n}=11\); poliomyelitis: 3, cerebral palsy: 3, multiple sclerosis: 2, brain tumor surgery: 1, spinocerebellar degeneration: 1, and traumatic brain injury: 1)