Table 1:

Summary of studies to date exploring epidural stimulation for blood pressure instability following spinal cord injury.

Orthostatic Hypotension management with Spinal Cord Electrical Stimulation
Study Author (date)	Number of Subjects/Animal Model	Participant Characteristics (human only)	Spinal Level of Stimulation, Frequency and Current	Measured Outcomes	Major Findings
Aslan et al. (2018)	N=3 hypotensive humans, N=4 normotensive humans	NLI= C5-T4 AIS= A, B Mean TSI= 2.7 years Mean Age= 26.7 years	L1-S1 epidural stimulation, 15–35 Hz, unknown mA	Arterial blood pressure during supine and manually assisted sitting.	Stimulation in three individuals with OH resulted in increased arterial blood pressure. Stimulation in four individuals without OH did not cause an increase in blood pressure.
Darrow et al. (2019)	N=2 humans	NLI= T4, T8 AIS= A Mean TSI= 7.5 years Mean Age= 50 years	L2-S2 epidural stimulation, 16–400 Hz, 2–15 mA	Arterial blood pressure during tilt challenge	Stimulation in one individual with OH resulted in increased blood pressure, while stimulation in another individual without OH did not affect cardiovascular function.
Harkema et al. (2018a)	N=4 humans	NLI= C4 AIS= A, B Mean TSI= 6.5 years Mean Age= 30.8 years	L1-S1 epidural stimulation, 30–60 Hz, unknown mA	Mean arterial blood pressure and heart rate in an upright, seated position.	Stimulation increased mean arterial pressure and decreased or kept heart rate constant.
Legg Ditterline et al. (2021)	N=4 humans † same individuals as Harkema et al. (2018a)	NLI= C4 AIS= A, B Mean TSI= 6.5 years Mean Age= 30.8 years	L1-S1 epidural stimulation, unknown Hz, unknown mA	Blood and heart rate variability, as well as baroreflex function with an orthostatic stress test. Circulating norepinephrine levels.	Stimulation increased blood pressure, heart rate variability and baroreceptor effectiveness. Norepinephrine levels unable to be detected at all time points, with and without stimulation.
Phillips et al. (2018)	N=5 humans	NLI= C5-T2 AIS= A, B Mean TSI= >3 years Mean Age= ? (range 23–32 years)	T8 transcutaneous stimulation, 30 Hz, up to 70 mA	Beat-to-beat blood pressure, heart rate during supine and manually assisted sitting. Blood flow velocity of MCA and PCA. Subjective rating of nausea/dizziness.	Stimulation increased blood pressure, heart rate, and MCA/PCA flow velocity compared nadir of orthostatic challenge. Decreased subjective ratings.
Squair et al. (2021)	N=3 rhesus monkeys N=1 human	NLI= C5 AIS= A TSI= ? Age= 38 years	T10-L1 epidural stimulation, 120 Hz, 0–7.5 mV variable	Beat-to-beat blood pressure, muscle sympathetic nerve activity, supine and in 70º tilt table. Circulating norepinephrine levels.	Blood pressure increased in proportion to calibrated stimulation. Reported increases in sympathetic nerve activity on microneurography and norepinephrine levels.
West et al. (2018)	N=1 human	NLI= C5 AIS= B TSI= ? Age= “early 30s”	T10-L2 epidural stimulation, 35 Hz constant, unknown mA	Beat-to-beat blood pressure, cardiac function in a supine position and then in response to a 60º head-up tilt.	Stimulation increased blood pressure and resolved OH.
Autonomic Dysreflexia management with Spinal Cord Electrical Stimulation
Study Author (date)	Number of Subjects/Animal Model	Participant Characteristics (humans only)	Spinal Level of Stimulation, Frequency and Current	Measured Outcomes	Major Findings
Collins et al. (2002)	N=11 rats	NA	T12-S3 TENS stimulation, 60 Hz, 600 μA	Blood pressure response to graded colon distension triggering AD with and without stimulation.	Attenuated the hemodynamic response to colon distension and decreased the change in arterial blood pressure.
Richardson et al. (1979)	N=5 humans	NLI*= ? AIS*= ? Mean TSI= 2.0 years Mean Age= 20.6 years	T12-L3 epidural stimulation, 7–200 Hz, 0.1–14V	Clinical findings only.	Case studies of five individuals with AD. Stimulation prevented further episodes of AD.
Sachdeva et al. (2021)	N= 43 rats N=1 human	NLI= C4 AIS= A TSI= 3 years Age= 37 years	T7–8 transcutaneous stimulation, 30 Hz, 20–30 mA (biphasic pulses)	Beat-to-beat blood pressure, heart rate during digital anorectal stimulation.	Prevention of AD and decrease in systolic pressure with stimulation compared to control.

NLI = neurological level of injury. AIS = American Spinal Injury Impairment Scale. TSI = time since injury. OH = orthostatic hypotension. MCA = middle cerebral artery. PCA = posterior cerebral artery. AD = autonomic dysreflexia. TENS = transcutaneous electrical nerve stimulation.

^*Based upon clinical data presented, predates AIS.