Citations

Abstract Background The T6 neurological level of spinal cord injury (SCI) is classically taught as differentiating who is and is not at risk for autonomic dysreflexia (AD); yet the reliability of this metric has rarely been tested. Objectives To determine how often individuals with SCI above and below the T6 neurological level of injury (NLI) experience symptomatic AD, quantify AD in the autonomic physiology laboratory, and describe underlying mechanisms that clinically manifest. Design Cross‐sectional. Setting Academic medical center. Participants 138 individuals with/without SCI. Interventions Not applicable. Main Outcome Measures Symptoms of AD were quantified using the validated Autonomic Dysfunction Following SCI‐AD survey. Deep autonomic physiology characterization was further completed ( n = 34 uninjured controls, n = 28 individuals with SCI) to identify underlying AD mechanisms. Continuous blood pressure, heart rate, regional vascular resistance in the arm/leg, and pre/posttest catecholamines were recorded. Vascular responsiveness and baroreflex sensitivity were assessed with intravenous phenylephrine boluses. Foot cold pressor and bladder pressor tests served as below level mild noxious stimuli to elicit controlled AD. Results AD symptoms were, as expected, significantly higher after SCI compared to uninjured controls ( p < .001). Symptomatic AD was identified in 77% of individuals with SCI at/above T6, compared to 38% with injuries below T6. McNemar's statistic indicated the T6 neurological level poorly differentiated who developed symptomatic AD ( p = .039). During laboratory testing, 57% of those with SCI at/above T6 experienced AD, as did 57% of those with injuries below T6 ( p = .33). Physiologically, AD in individuals with SCI below T6 can be due to heightened vascular responsiveness and poor baroreflex sensitivity, leading to minimal compensatory bradycardia. Conclusions Symptomatic and objective AD occurs in those with SCI above and below the T6 NLI threshold. As such, targeted autonomic testing must translate to the bedside to accurately quantify AD risk. In the interim, though the T6 threshold has become cannon in many patient and resident education materials regarding AD risk, evidence suggests clinical care should avoid using this strict cutoff.

ABSTRACT Introduction/Aims Patients with cervical spinal cord injury (SCI) prioritize recovery of upper extremity function. Upper extremity reconstruction can restore function in carefully selected individuals. Infralesional cord damage, observed below the neurological level of injury (NLI), may affect postoperative outcomes. We characterized the extent of infralesional lower motor neuron (LMN) injury in patients with traumatic cervical SCI. Methods Each patient underwent electromyography (EMG) of potential donor and recipient muscles based on preoperative clinical evaluation and specific candidacy for nerve and/or tendon transfers. The presence of infralesional pathologic insertional activity (IA), reduced motor unit potential (MUP) recruitment and/or neurogenic MUPs was assessed. The caudal‐most segment with infralesional LMN injury was determined. Inclusion criteria were patients with (1) traumatic cervical SCI; (2) injury ≥ 3 months duration; (3) preoperative planning EMG for nerve and/or tendon transfers. Results Forty‐eight upper extremity EMGs in 25 patients (68% male; mean age 39.5 years at injury) with traumatic cervical SCI were included. The NLI was at C7 or above in each patient, and 64% of SCIs were motor complete. Infralesional EMG abnormalities (median time from injury to EMG 466 days) were found a median of 3.0 (IQR 3.0–4.0) segments below the NLI. Three patients with an NLI as rostral as C1–C2 exhibited LMN injury seven segments below the NLI. Discussion In persons with traumatic cervical SCI, evidence of LMN injury may be observed several segments below the NLI. Defining the true extent of LMN involvement directly informs timing and selection of reconstructive procedures to maximize functional recovery.

Study objective: To characterize physiologic autonomic dysfunction in humans after chronic spinal cord injury (SCI) relative to uninjured controls and to identify autonomic correlates to neuroimmune deficits. Hypothesis: Individuals with greater autonomic dysfunction after SCI will have more pronounced immune dysfunction, which will be further influenced by sympathetically mediated increases in catecholamine levels. Methodology: Both uninjured controls and individuals with SCI completed a battery of autonomic physiology tests aimed at characterizing preservation of supralesional/sublesional sympathetic activation and global sympathetic inhibition. The autonomic testing battery included 3-minute hand and foot cold pressor tests, 3 Valsalva maneuvers with goal expiratory pressure of 30 mmHg, a novel bladder pressor test (5 minutes of sustained bladder pressure at 35 cmH20 with room temperature sterile water infusion), paced breathing at 0.25 Hz for heart rate/blood pressure variability, and successive doses of bolus intravenous phenylephrine (Oxford technique). A subset of individuals in both cohorts had baseline and cold pressor stressed levels of catecholamines/cortisol drawn and immunologic assessments. Peripheral blood mononuclear cells were extracted from this baseline sample and assessed with flow cytometry for cellular exhaustion markers (CD69, PD-1, TIGIT, TIM-3). Antigen recall response, with/without primed exposure of catecholamines was also completed to identify how sympathetic activation variably impacted functional immune performance with exposure to viral peptides. Data: n=35 uninjured controls; n=29 individuals with SCI Summary of Results: When compared to uninjured controls, individuals with SCI demonstrated significant autonomic dysfunction in all three domains, with decreased supralesional sympathetic activation (Valsalva pressure recovery time, p< 0.0001), abnormal sublesional sympathetic activation (increased bradycardia, p< 0.0001), and impaired sympathetic inhibition (larger dose/body-weight adjusted increase in mean arterial pressure, p=0.0006). As expected, autonomic dysfunction in those with SCI existed on a continuum, with some having largely normal autonomic regulation and others exhibiting profound deficits. Principal component analysis confirmed these three domains as the primary drivers of variability. Cellular exhaustion markers were increased in those with SCI, with positive correlation (R2=0.42) between degree of global autonomic dysfunction (Z-score over 2.0) and CD3+ CD8+ T-cell TIM-3 immunologic exhaustion markers. Antigen recall response was impaired in those with SCI and autonomic dysfunction on physiologic testing, with pronounced decrement in response when catecholamines were added (mean 57% of response lost in CD69 T-cells to Epstein-Barr virus antigen exposure, 53% lost to Flu antigen). Conclusions: In humans with SCI, early evidence supports that individuals have greater autonomic dysfunction and that this is correlated to increased immunologic deficits. Funding Sources: NIH K23HD102663, R01NS115126 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Objective To evaluate the feasibility and potential efficacy of percutaneous spinal stimulation (epidural stimulation, ES) combined with task-specific training to reduce spasticity and improve gait and balance in individuals with progressive multiple sclerosis (MS). Methods Two men with progressive MS (EDSS 6.5) underwent ES lead implantation targeting the lower spinal cord, followed by one month of rehabilitation involving 12 ES-assisted training sessions. Assessments included instrumented gait analysis, Modified Ashworth Scale (MAS), pendulum test, and static balance testing performed at baseline, and at end of the study with ES-Off and ES-On conditions. Results Participant 1, with spastic hemiparetic gait, demonstrated improved lower extremity joint kinematics and muscle activation during gait, reduced knee extensor spasticity, and enhanced functional movement patterns with ES-On. Participant 2, with significant paraparesis and minimal spasticity, showed limited gait changes but experienced marked improvements in static balance, particularly under eyes-closed conditions. No adverse events were reported. Conclusion This pilot study demonstrates the feasibility and tolerability of ES paired with task-specific training in progressive MS. Participant-specific responses were observed, including improvements in gait kinematics, neuromuscular activation, spasticity, or balance; however, spatiotemporal gait parameters did not improve. These preliminary findings highlight response heterogeneity and the need for individualized ES parameter tuning. Trial registry name and URL: https://clinicaltrials.gov/study/NCT06019611

Epidural and dorsal root stimulation have emerged as promising therapies to restore function after spinal cord injury. However, how each modality uniquely or jointly engages spinal circuits remains unclear. To address this, we analyzed leg electromyography (EMG) responses to epidural stimulation (ES) and dorsal root ganglia stimulation (DRGS) delivered to the lumbosacral cord in the same individuals.

The expanding application of spinal stimulation therapies in spinal cord injury (SCI) rehabilitation necessitates a critical reexamination of cardiovascular (CV) responses to these interventions. A key question arises: How should blood pressure (BP) responses to stimulation be interpreted, and does the conventional definition of autonomic dysreflexia (AD) adequately capture these phenomena? Researchers remain divided—some classify BP elevations during stimulation as AD, while others attribute them to intentional neuromodulation targeting sympathetic preganglionic neurons. This review scrutinizes the various AD definitions in the literature, including the conventional threshold (systolic BP increase >20 mmHg), revealing substantial limitations in research contexts. While symptomatic AD occurs in only 4-7% of stimulation study participants, asymptomatic BP increases are considerably more frequent. This established threshold lacks robust physiological rationale and creates significant interpretive challenges, particularly when evaluating interventions designed to modulate BP responses. The current limitations of guideline-based definitions of AD challenge research interpretation and clinical translation. Although several publications describe AD as “unregulated” or “uncontrolled,” it has not yet been incorporated into formal guideline definitions. This review underscores the need for a collaborative effort to refine AD definitions in research, particularly in the context of spinal stimulation. Future consensus development should address whether uniform thresholds should apply across different contexts, how to integrate heart rate dynamics and absolute BP values alongside symptomatic status, and how to meaningfully distinguish therapeutic BP modulation from adverse autonomic responses. This is essential for standardizing research approaches, optimizing stimulation parameters, and ensuring efficacy and safety as spinal stimulation technologies advance clinically.

Abstract Background Individuals with spinal cord injury (SCI) are known to have high rates of cardiovascular disease that have traditionally been attributed to inability to engage in adequate intensity exercise. However, individuals with SCI also commonly experience instability in blood pressure. Blood pressure fluctuations are known to contribute to cardiovascular disease in other conditions, though this relationship in SCI is unknown. Objective To evaluate correlations between a clinical history of symptomatic blood pressure instability and objective evidence of vascular endothelial dysfunction in individuals with SCI. Design Case control. Setting Academic medical center. Participants Twenty‐four individuals with SCI, 14 uninjured controls of matched age, gender, and body mass index. Interventions Not applicable. Main Outcome Measures Symptomatic blood pressure instability was measured by the Autonomic Dysfunction Following SCI (ADFSCI) survey. Vascular endothelial dysfunction was quantified by ultrasound recordings of brachial flow mediated dilation following 5 minutes of forearm arterial occlusion. Results Total ADFSCI scores were significantly higher in individuals with SCI compared to controls (41.0 vs. 9.0, p = .002). Both percentage of brachial flow mediated dilation and consensus recommended allometrically scaled percentage of flow mediated dilation were significantly less in individuals with SCI ( p < .001 for both), demonstrating greater vascular dysfunction. More symptoms of blood pressure instability on the ADFSCI survey were correlated with more objective evidence of vascular dysfunction ( R 2 = 0.24, p = .03) for individuals with SCI. This relationship was not seen in uninjured controls. Conclusions In individuals with SCI, more severe symptoms of blood pressure instability are significantly correlated with more severe vascular endothelial dysfunction, making management of orthostatic hypotension and autonomic dysreflexia both high potential, modifiable risk factors for individuals with SCI to mitigate cardiovascular disease.

Background: Emerging neuromodulation approaches, including epidural electrical stimulation (EES), offer hope for restoration of function following chronic spinal cord injury (SCI). However, integrating neuromodulation therapies into clinical procedures is challenging due to the unique needs of the SCI population. Objectives: The purpose of this study was to understand the experiences of participants during a first-in-human trial of perilesional EES aimed at restoring sensorimotor function. Methods: We report participants’ experiences by describing their clinical care, experiences during experimental neuromodulation sessions, and perspectives on the utility of a perilesional EES system. Three participants with chronic thoracic SCI participated in semistructured interviews after completing a 14-day inpatient experimental protocol, which included stimulation mapping, lower extremity motor control experiments, and treadmill stepping. Interview data were analyzed using an applied thematic analysis approach. Nine key themes addressed 4 major topic areas: clinical experiences, experiences during laboratory experiments, experiences as a research participant, and perceived value of perilesional EES. Results: All participants noted the potential for EES to enhance functional recovery, though their postoperative experiences related to clinical care, postoperative pain, and disruptions to routine care differed. Insights gained from qualitative analyses highlighted challenges and opportunities for improving postsurgical care and refining application of EES technology. Further, these results inform recommendations for neuromodulation trials in the SCI community to help mitigate postoperative complications and improve study participant experiences. Conclusion: Key recommendations include being proactive regarding potential postsurgical complications, educating clinical staff regarding common SCI comorbidities, and customizing experimental protocols to align with the priorities and clinical needs of each participant.

Abstract Background After high‐level spinal cord injury (SCI), motor recovery of wrist extensors has significant functional consequences as it can facilitate grasp through tenodesis. A small seminal study from 1993 established widely used prognostic rules for wrist extensor recovery, though these have not been replicated with larger, real‐world samples since inception. Objective To determine the prognostic value of initial C5 sharp‐dull discrimination, C5 motor strength, and C6 motor strength on predicting 1‐year ipsilateral wrist extensor motor recovery for patients with SCI with neurological level of C4 or C5. Design Retrospective cohort replication study. Setting SCI Model Systems. Participants 35,675 total individuals with acute traumatic SCI with 219 cases of initial wrist extensor weakness (0/5–2/5) meeting inclusion criteria. Intervention Not applicable. Main outcome measure Recovery of wrist extensor strength to ≥3/5 at 1 year. Results The positive predictive and negative predictive values were 57% (95% CI, 47.4%–66.1%) and 66% (56.0%–75.1%) if initial C5 sharp‐dull discrimination was present, 61% (52.7%–69.3%) and 82% (71.4%–89.7%) if initial C5 myotome strength was at least antigravity, and 74% (63.7%–82.5%) and 74% (65.5%–81.4%) if initial C6 myotome strength was at least a 1/5 or 2/5. Synthesizing these three rules, an updated branched nomogram for functional wrist extensor recovery prediction was created. Conclusions In isolation, none of the previously established wrist extensor motor recovery predictive rules had as high of a prognostic value when using a larger dataset. As such, singular reliance on these prediction rules to identify who will gain 1‐year antigravity wrist extension should be approached with decreased certainty. The best positive and negative predictors were trace C6 strength and absent C5 strength, respectively. An updated nomogram provides more nuanced prognostic information to guide clinical care following acute SCI.