Table 2. Characteristics of studies assessing the effects of VR on neuropathic pain in people with spinal cord injury. Abbreviations: BPI, Brief Pain Inventory; HMD, head-mounted device; NP, neuropathic pain; NRS, Numerical Rating Scale; QST, quantitative sensory testing; SCI, spinal cord injury; tDCS, transcranial direct current stimulation; TENS, transcutaneous electrical nerve stimulation; VR, virtual reality; VAS, Visual Analogue Scale.

First author	Date	Objectives	Study type	Sample	Modality (VR/AR)	Interface	VR treatment application	Dose	Key Findings
Pozeg P	2017	Changes in body ownership and neuropathic pain	Case-control	SCI (paraplegia) healthy controls	VR	HMD	Virtual leg and b) full body illusion b) Synchronous and asynchronous tactile stimuli to back and virtual leg	2×2 repeated measure (60 s)	leg ownership decreases with time since SCI small reduction in neuropathic pain (P = 0.04)
Donati A	2016	Explore long-term motor and sensory effects of brain-machine interfaces in SCI patients with paraplegia	Exploratory single cohort	8 chronic SCI (paraplegia) patients	Lower limb exoskeleton VR avatar	Robotic device HMD	Virtual legs and arm movement	12 months (663 h – neuro-rehab training)	Neurological improvements in Pain intensity (P = 0.01) Fine/crude touch (P = 0.05) Proprioceptive sensing (no P value) Voluntary muscle control in muscles below lesion level (P = 0.01)
Jordan M	2016	Investigate effects of VR walking on below-level SCI pain compared to at level SCI pain	Single cohort (randomized selection from larger sample)	15 of 35 SCI	VR	3D monitor	Virtual walking (treatment) / wheeling (control) virtual wheeling (control)	20-minute video	Greater decrease in at-level pain (P = 0.08) Larger decrease in pain during VR walking compared to VR wheeling (P = 0.03)
Roosink M	2016	Assess immediate effect of interactive virtual feedback and motor imagery after SCI	Exploratory Single cohort	9 SCI	VR	3D screen	Interactive and static virtual walking (forward and backward) in a virtual scene	X 2 sessions (90 min each) 1 week apart	No change in pain intensity Motor imagery (vividness/speed) – significantly higher compared to a static virtual scene (P = 0.03)
Villiger M	2013	Assess effect of VR-augmented movement on motor function and neuropathic pain	Single cohort	14 Incomplete SCI	VR	3D monitor	Foot and leg movement (foot and hand sensors) using 4 VR movement exercises	16–20 sessions (45 min), 4–5 times / week for 4 weeks	Increased muscle strength (P = 0.001) Increased mobility (P = 0.004) Decreased pain intensity (P = 0.004), Decreased pain unpleasantness (P = 0.004)
Moseley L	2007	Investigate effect of visual illusion for the treatment of neuropathic SCI pain	Exploratory single cohort	5 SCI (paraplegia)	VR	2D screen	Virtual walking (actor legs, patients’ upper body) Guided imagery Animated comedy (placebo)	X 3 10-minute visual conditions Virtual walking daily for 3 weeks	Virtual walking (decrease of 42 on 0–100 VAS) Daily virtual walking (decrease of 52 on a 0–100 VAS)
Kumru H	2013	Assess whether pain relief with tDCS + VR interventions is accompanied by changes in thermal QST scores	Case-control	SCI patients with NP SCI patients with no NP healthy controls	VR	2D screen	Virtual walking (actor legs, patients’ upper body) Guided imagery	X 10, 20-minute sessions over 2 weeks	Average decrease in pain intensity (NRS) after tDCS + VR compared to baseline (37% = P < 0.05) No significant difference in evoked heat pain perception between SCI NP and non-NP groups
Soler M	2010	Evaluate analgesic effect of tDCS + VR interventions applied in isolation or in combination	Single cohort	40 SCI patients with NP		2D screen	Virtual walking (actor legs, patients’ upper body) Guided imagery Graphical landscapes (placebo)	X 10, 20-minute sessions over 2 weeks	SCI patients receiving tDCS + VR showed significant decreases in NP (NRS) compared to single interventions (P < 0.005) At 12-week follow up, tDCS + VR showed maintained decreases in pain intensity (P < 0.05) Single treatments show no improvements at 12-week follow up
Özkul C	2014	Compare effects of VR and TENS on pain intensity, quality and functional capacity	Single cohort	24 SCI patients with NP		2D screen	Virtual walking (actor legs, patients’ upper body) Guided imagery	X 10 15-minute sessions over 2 weeks	Immediate pain relief after VR and TENS (VAS) (P < 0.05). Significant decrease in NP after 2 weeks with TENS, but not VR (P < 0.05) Significant decrease in pain quality (hot, sharp, unpleasantness) with VR but not TENS at 2 weeks (P < 0.05) Significant increase in functional capacity with VI at 2 weeks (BPI) (P < 0.05)