Width and neurophysiologic properties of tissue bridges predict recovery after cervical injury

Extent of Traumatic Spinal Cord Injury Is Lesion Level Dependent and Predictive of Recovery: A Multicenter Neuroimaging Study

Assessing the extent of the intramedullary lesion after spinal cord injury (SCI) might help to improve prognostication. However, because the neurological level of injury impacts the recovery potential of SCI patients, the question arises whether lesion size parameters and predictive models based on those parameters are affected as well. In this retrospective observational study, the extent of the intramedullary lesion between individuals who sustained cervical and thoracolumbar SCI was compared, and its relation to clinical recovery was assessed. In total, 154 patients with subacute SCI (89 individuals with cervical lesions and 65 individuals with thoracolumbar lesions) underwent conventional clinical magnetic resonance imaging 1 month after injury and clinical examination at 1 and 12 months. The morphology of the focal lesion within the spinal cord was manually assessed on the midsagittal slice of T2-weighted magnetic resonance images and compared between cervical and thoracolumbar SCI patients, as well as between patients who improved at least one American Spinal Injury Association Impairment Scale (AIS) grade (converters) and patients without AIS grade improvement (nonconverters). The predictive value of lesion parameters including lesion length, lesion width, and preserved tissue bridges for predicting AIS grade conversion was assessed using regression models (conditional inference tree analysis). Lesion length was two times longer in thoracolumbar compared with cervical SCI patients (F = 39.48, p < 0.0001), whereas lesion width and tissue bridges width did not differ. When comparing AIS grade converters and nonconverters, converters showed a smaller lesion length (F = 5.46, p = 0.021), a smaller lesion width (F = 13.75, p = 0.0003), and greater tissue bridges (F = 12.87, p = 0.0005). Using regression models, tissue bridges allowed more refined subgrouping of patients in AIS groups B, C, and D according to individual recovery profiles between 1 month and 12 months after SCI, whereas lesion length added no additional information for further subgrouping. This study characterizes differences in the anteroposterior and craniocaudal lesion extents after SCI. The two times greater lesion length in thoracolumbar compared with cervical SCI might be related to differences in the anatomy, biomechanics, and perfusion between the cervical and thoracic spines. Preserved tissue bridges were less influenced by the lesion level while closely related to the clinical impairment. These results highlight the robustness and utility of tissue bridges as a neuroimaging biomarker for predicting the clinical outcome after SCI in heterogeneous patient populations and for patient stratification in clinical trials.

Prognostic value of tissue bridges in cervical spinal cord injury: a longitudinal, multicentre, retrospective cohort study

BACKGROUND

The accuracy of prognostication in patients with cervical spinal cord injury (SCI) needs to be improved. We aimed to explore the prognostic value of preserved spinal tissue bridges-injury-spared neural tissue adjacent to the lesion-for prediction of sensorimotor recovery in a large, multicentre cohort of people with SCI.

METHODS

For this longitudinal study, we included patients with acute cervical SCI (vertebrae C1-C7) admitted to one of three trauma or rehabilitation centres: Murnau, Germany (March 18, 2010-March 1, 2021); Zurich, Switzerland (May 12, 2002-March 2, 2019); and Denver, CO, USA (Jan 12, 2010-Feb 16, 2017). Patients were clinically assessed at admission (baseline), at discharge (3 months), and at 12 months post SCI. Midsagittal tissue bridges were quantified from T2-weighted images assessed at 3-4 weeks post SCI. Fractional regression and unbiased recursive partitioning models, adjusted for age, sex, centre, and neurological level of injury, were used to assess associations between tissue bridge width and baseline-adjusted total motor score, pinprick score, and light touch scores at 3 months and 12 months. Patients were stratified into subgroups according to whether they showed better or worse predicted recovery.

FINDINGS

The cohort included 227 patients: 93 patients from Murnau (22 [24%] female); 43 patients from Zurich (four [9%] female); and 91 patients from Denver (14 [15%] female). 136 of these participants (from Murnau and Zurich) were followed up for up to 12 months. At 3 months, per preserved 1 mm of tissue bridge at baseline, patients recovered a mean of 9·3% (SD 0·9) of maximal total motor score (95% CI 7·5-11.2), 8·6% (0·8) of maximal pinprick score (7·0-10·1), and 10·9% (0·8) of maximal light touch score (9·4-12·5). At 12 months post SCI, per preserved 1 mm of tissue bridge at baseline, patients recovered a mean of 10·9% (1·3) of maximal total motor score (8·4-13·4), 5·7% (1·3) of maximal pinprick score (3·3-8·2), and 6·9% (1·4) of maximal light touch score (4·1-9·7). Partitioning models identified a tissue bridge cutoff width of 2·0 mm to be indicative of higher or lower 3-month total motor, pinprick, and light touch scores, and a cutoff of 4·0 mm to be indicative of higher and lower 12-month scores. Compared with models that contained clinical predictors only, models additionally including tissue bridges had significantly improved prediction accuracy across all three centres.

INTERPRETATION

Tissue bridges, measured in the first few weeks after SCI, are associated with short-term and long-term clinical improvement. Thus, tissue bridges could potentially be used to guide rehabilitation decision making and to stratify patients into more homogeneous subgroups of recovery in regenerative and neuroprotective clinical trials.

FUNDING

Wings for Life, International Foundation for Research in Paraplegia, EU project Horizon 2020 (NISCI grant), and ERA-NET NEURON.

Lesion characteristics are associated with bowel, bladder, and overall independence following cervical spinal cord injury

CONTEXT/OBJECTIVE

There is a growing global interest in quantifying spinal cord lesions and spared neural tissue using magnetic resonance imaging (MRI) in individuals with spinal cord injury (SCI). The primary objective of this study was to assess the relationships between spinal cord lesion characteristics assessed on MRI and bowel, bladder, and overall independence following SCI.

DESIGN

Retrospective, exploratory study.

PARTICIPANTS

93 individuals with cervical SCI who were enrolled in a local United States Model Systems SCI database from 2010 to 2017.

METHODS

Clinical and MRI data were obtained for potential participants, and MRIs of eligible participants were analyzed. Explanatory variables, captured on MRIs, included intramedullary lesion length (IMLL), midsagittal ventral tissue bridge width (VTBW), midsagittal dorsal tissue bridge width (DTBW), and axial damage ratio (ADR).

OUTCOME MEASURES

Bowel and bladder management scale of the Functional Independence Measure (FIM) and FIM total motor score.

RESULTS

When accounting for all four variables, only ADR was significantly associated with bowel independence (OR = 0.970, 95% CI: 0.942-0.997, P = 0.030), and both ADR and IMLL were strongly associated with bladder independence (OR = 0.967, 95% CI: 0.936-0.999, P = 0.046 and OR = 0.948, 95% CI: 0.919-0.978, P = 0.0007, respectively). 32% of the variation in overall independence scores were explained by all four predictive variables, but only ADR was significantly associated with overall independence after accounting for all other predictive variables (β = -0.469, 95% CI: -0.719, -0.218, P = 0.0004).

CONCLUSIONS

Our results suggest that the MRI-measured extent of spinal cord lesion may be predictive of bowel, bladder, and overall independence following cervical SCI.

Wallerian Degeneration Assessed by Multi-Modal Magnetic Resonance Imaging of Cervical Spinal Cord Is Associated With Neurological Impairment After Spinal Cord Injury

While Wallerian degeneration (WD) is a crucial pathological process induced with spinal cord injury (SCI), its underlying mechanisms is still understudied. In this study, we aim to assess structural alterations and clinical significance of WD in the cervical cord following SCI using multi-modal magnetic resonance imaging (MRI), which combines T2*-weighted imaging and diffusion tensor imaging (DTI). T2*-weighted images allow segmentation of anatomical structures and the detection of WD on macrostructural level. DTI, on the other hand, can identify the reduction in neuroaxonal integrity by measuring the diffusion of water molecules on the microstructural level. In this prospective study, 35 SCI patients (19 paraplegic and 16 tetraplegic patients) and 12 healthy controls were recruited between July 2020 and May 2022. The hyperintensity voxels in the dorsal column was manually labeled as WD on T2*-weighted images. The mean cross-sectional area (CSA) and mean DTI indexes of WD at the C2 level were calculated and compared between groups. Correlation analysis was used to determine the associations of the magnitude of WD with lesion characteristics and clinical outcomes. Compared with controls, SCI patients showed evident hyperintensity (35/35) and decreased neuroaxonal integrity (p < 0.05) within the dorsal column at the C2 level. A higher neurological level of injury was associated with a larger mean CSA and reduction in neuroaxonal integrity within WD (p < 0.05). Smaller total and dorsal tissue bridges were related to greater mean CSA and lower fractional anisotropy values in WD (p < 0.05), respectively. Moreover, SCI participants with significantly larger CSAs and significantly lower microstructural integrity had worse sensory outcomes (p < 0.05). This comprehensive evaluation of WD can help us better understand the mechanisms of WD, monitor progression, and assess the effectiveness of therapeutic interventions after SCI.

SCIseg: Automatic Segmentation of T2-weighted Intramedullary Lesions in Spinal Cord Injury

Purpose

To develop a deep learning tool for the automatic segmentation of T2-weighted intramedullary lesions in spinal cord injury (SCI).

Material and Methods

This retrospective study included a cohort of SCI patients from three sites enrolled between July 2002 and February 2023. A deep learning model, SCIseg, was trained in a three-phase process involving active learning for the automatic segmentation of intramedullary SCI lesions and the spinal cord. The data consisted of T2-weighted MRI acquired using different scanner manufacturers with heterogeneous image resolutions (isotropic/anisotropic), orientations (axial/sagittal), lesion etiologies (traumatic/ischemic/hemorrhagic) and lesions spread across the cervical, thoracic and lumbar spine. The segmentations from the proposed model were visually and quantitatively compared with other open-source baselines. Wilcoxon signed-rank test was used to compare quantitative MRI biomarkers (lesion volume, lesion length, and maximal axial damage ratio) computed from manual lesion masks and those obtained automatically with SCIseg predictions.

Results

MRI data from 191 SCI patients (mean age, 48.1 years ± 17.9 [SD]; 142 males) were used for model training and evaluation. SCIseg achieved the best segmentation performance for both the cord and lesions. There was no statistically significant difference between lesion length and maximal axial damage ratio computed from manually annotated lesions and those obtained using SCIseg.

Conclusion

Automatic segmentation of intramedullary lesions commonly seen in SCI replaces the tedious manual annotation process and enables the extraction of relevant lesion morphometrics in large cohorts. The proposed model segments lesions across different etiologies, scanner manufacturers, and heterogeneous image resolutions. SCIseg is open-source and accessible through the Spinal Cord Toolbox.

Longitudinal motor system changes from acute to chronic spinal cord injury

BACKGROUND AND PURPOSE

In acute spinal cord injury (SCI), magnetic resonance imaging (MRI) reveals tissue bridges and neurodegeneration for 2 years. This 5-year study aims to track initial lesion changes, subsequent neurodegeneration, and their impact on recovery.

METHODS

This prospective longitudinal study enrolled acute SCI patients and healthy controls who were assessed clinically-and by MRI-regularly from 3 days postinjury up to 60 months. We employed histologically cross-validated quantitative MRI sequences sensitive to volume, myelin, and iron changes, thereby reflecting indirectly processes of neurodegeneration and neuroinflammation. General linear models tracked lesion and remote changes in volume, myelin- and iron-sensitive magnetic resonance indices over 5 years. Associations between lesion, degeneration, and recovery (using the Spinal Cord Independence Measure [SCIM] questionnaire and the International Standards for Neurological Classification of Spinal Cord Injury total motor score) were assessed.

RESULTS

Patients' motor scores improved by an average of 12.86 (95% confidence interval [CI] = 6.70-19.00) points, and SCIM by 26.08 (95% CI = 17.00-35.20) points. Within 3-28 days post-SCI, lesion size decreased by more than two-thirds (3 days: 302.52 ± 185.80 mm2 , 28 days: 76.77 ± 88.62 mm2 ), revealing tissue bridges. Cervical cord and corticospinal tract volumes transiently increased in SCI patients by 5% and 3%, respectively, accompanied by cervical myelin decreases and iron increases. Over time, progressive atrophy was observed in both regions, which was linked to early lesion dynamics. Tissue bridges, reduced swelling, and myelin content decreases were predictive of long-term motor score recovery and improved SCIM score.

CONCLUSIONS

Studying acute changes and their impact on longer follow-up provides insights into SCI trajectory, highlighting the importance of acute intervention while indicating the potential to influence outcomes in the later stages.

History and Accomplishments of the North American Clinical Trials Network for Spinal Cord Injury, 2004-2022

This is a historical account of the origin and accomplishments of the North American Clinical Trials Network (NACTN) for traumatic spinal cord injury (SCI), which was established in 2004 by Christopher Reeve and Robert Grossman. Christopher Reeve was an actor who became quadriplegic and started the Christopher & Dana Reeve Foundation (CDRF), and Robert Grossman was a neurosurgeon experienced in neurotrauma and a university professor in Houston. NACTN has member investigators at university and military centers in North America and has contributed greatly to the improvement of care, primarily acute care, of patients sustaining traumatic SCI. Its accomplishments are a clinical registry database of >1000 acute SCI patients documenting the care pathways, including complications. NACTN has assessed the effectiveness of treatment, including pharmacotherapy and the role and timing of surgery, and has also identified barriers to early surgery. The principal focus has been on improving neurological recovery. NACTN has trained many SCI practitioners and has collaborated with other SCI networks and organizations internationally to promote the care of SCI patients.

The presence or absence of midsagittal tissue bridges and walking: a retrospective cohort study in spinal cord injury

STUDY DESIGN

Cohort study. Retrospective analysis of T2-weighted magnetic resonance images (MRIs) and clinical documentation.

OBJECTIVES

To evaluate the relationship between the presence/absence and widths of midsagittal tissue bridges and walking ability among veterans with cervical, predominantly chronic SCI.

SETTING

University research and hospital setting.

METHODS

T2-weighted midsagittal MRIs of 22 United States veterans with cervical spinal cord injuries were examined. The presence/absence of midsagittal tissue bridges were determined, and the widths of present ventral and dorsal tissue bridges were measured. Midsagittal tissue bridge characteristics were related to each participant's ability to walk based off examination of clinical documentation.

RESULTS

Fourteen of the analyzed participant images revealed the presence of midsagittal tissue bridges. Ten of those individuals (71%) possessed overground walking ability. The 8 individuals with no apparent tissue bridges were all unable to walk. There was a significant correlation between walking and widths of ventral midsagittal tissue bridges (r = 0.69, 95%CI: 0.52, 0.92, p < 0.001), as well as dorsal midsagittal tissue bridges (r = 0.44, 95%CI: 0.15, 0.73, p = 0.039).

CONCLUSION

The evaluation of midsagittal tissue bridges may be useful in various rehabilitation settings to help inform patients' plan of care, allocation of neuromodulatory resources, and appropriate stratification into research cohorts.

Stimulation of the cuneiform nucleus enables training and boosts recovery after spinal cord injury

Severe spinal cord injuries result in permanent paraparesis in spite of the frequent sparing of small portions of white matter. Spared fibre tracts are often incapable of maintaining and modulating the activity of lower spinal motor centres. Effects of rehabilitative training thus remain limited. Here, we activated spared descending brainstem fibres by electrical deep brain stimulation of the cuneiform nucleus of the mesencephalic locomotor region, the main control centre for locomotion in the brainstem, in adult female Lewis rats. We show that deep brain stimulation of the cuneiform nucleus enhances the weak remaining motor drive in highly paraparetic rats with severe, incomplete spinal cord injuries and enables high-intensity locomotor training. Stimulation of the cuneiform nucleus during rehabilitative aquatraining after subchronic (n = 8 stimulated versus n = 7 unstimulated versus n = 7 untrained rats) and chronic (n = 14 stimulated versus n = 9 unstimulated versus n = 9 untrained rats) spinal cord injury re-established substantial locomotion and improved long-term recovery of motor function. We additionally identified a safety window of stimulation parameters ensuring context-specific locomotor control in intact rats (n = 18) and illustrate the importance of timing of treatment initiation after spinal cord injury (n = 14). This study highlights stimulation of the cuneiform nucleus as a highly promising therapeutic strategy to enhance motor recovery after subchronic and chronic incomplete spinal cord injury with direct clinical applicability.

Correlation Analysis Between Magnetic Resonance Imaging-Based Anatomical Assessment and Behavioral Outcome in a Rat Contusion Model of Chronic Thoracic Spinal Cord Injury

Although plenty of evidences from preclinical studies have led to potential treatments for patients with spinal cord injury (SCI), the failure to translate promising preclinical findings into clinical advances has long puzzled researchers. Thus, a more reliable combination of anatomical assessment and behavioral testing is urgently needed to improve the translational worth of preclinical studies. To address this issue, the present study was designed to relate magnetic resonance imaging (MRI)-based anatomical assessment to behavioral outcome in a rat contusion model. Rats underwent contusion with three different heights to simulate various severities of SCI, and their locomotive functions were evaluated by the grid-walking test, Louisville swim scale (LSS), especially catwalk gait analysis system and basic testing, and Basso, Beattie, Bresnahan (BBB) score. The results showed that the lesion area (LA) is a better indicator for damage assessment compared with other parameters in sagittal T2-weighted MRI (T2WI). Although two samples are marked as outliers by the box plot analysis, LA correlated closely with all of the behavioral testing without ceiling effect and floor effect. Moreover, with a moderate severity of SCI in a contusion height of 25 mm, the smaller the LA of the spinal cord measured on sagittal T2WI the better the functional performance, the smaller the cavity region and glial scar, the more spared the myelin, the higher the volatility, and the thicker the bladder wall. We found that LA significantly related with behavior outcomes, which indicated that LA could be a proxy of damage assessment. The combination of sagittal T2WI and four types of behavioral testing can be used as a reliable scheme to evaluate the prognosis for preclinical studies of SCI.

Transcutaneous Electrical Spinal Cord Stimulation to Promote Recovery in Chronic Spinal Cord Injury

Objective: To evaluate the impact of using transcutaneous electrical spinal cord stimulation (TSCSTSCS) on upper and lower extremity function in individuals with chronic spinal cord injury (SCI).

Design: Prospective case series.

Setting: SCI specific rehabilitation hospital.

Participants: A convenience sample (N = 7) of individuals with tetraplegia who had previously been discharged from outpatient therapy due to a plateau in progress.

Interventions: Individuals participated in 60 min of upper extremity (UE) functional task-specific practice (FTP) in combination with TSCS and 60 min of locomotor training in combination with TSCS 5x/week.

Main Outcome Measures: The primary outcome for this analysis was the Capabilities of Upper Extremity Test (CUE-T). Secondary outcomes include UE motor score (UEMS), LE motor score (LEMS), sensation (light touch and pin prick), Nine-Hole Peg Test, 10 meter walk test, 6 min walk test, and 5 min stand test.

Results: Seven individuals (four motor complete; three motor incomplete) completed 20–80 sessions UE and LE training augmented with TSCS and without any serious adverse events. Improvements were reported on the CUE-T in all seven individuals. Two individuals improved their ASIA impairment scale (AIS) classification (B to C; C to D) and two individuals improved their neurologic level of injury by one level (C4–C5; C5–C6). Sensation improved in five individuals and all four who started out with motor complete SCIs were able to voluntarily activate their LEs on command in the presence of stimulation.

Conclusion: Individuals with chronic SCI who had previously demonstrated a plateau in function after an intensive outpatient therapy program were able to improve in a variety of UE and LE outcomes in response to TSCS without any adverse events. This was a small pilot study and future fully powered studies with comparative interventions need to be completed to assess efficacy.

Spinal Cord Tissue Bridges Validation Study: Predictive Relationships With Sensory Scores Following Cervical Spinal Cord Injury

Background

Using magnetic resonance imaging (MRI), widths of ventral tissue bridges demonstrated significant predictive relationships with future pinprick sensory scores, and widths of dorsal tissue bridges demonstrated significant predictive relationships with future light touch sensory scores, following spinal cord injury (SCI). These studies involved smaller participant numbers, and external validation of their findings is warranted.

Objectives

The purpose of this study was to validate these previous findings using a larger independent data set.

Methods

Widths of ventral and dorsal tissue bridges were quantified using MRI in persons post cervical level SCI (average 3.7 weeks post injury), and pinprick and light touch sensory scores were acquired at discharge from inpatient rehabilitation (average 14.3 weeks post injury). Pearson product-moments were calculated and linear regression models were created from these data.

Results

Wider ventral tissue bridges were significantly correlated with pinprick scores (r = 0.31, p < 0.001, N = 136) and wider dorsal tissue bridges were significantly correlated with light touch scores (r = 0.31, p < 0.001, N = 136) at discharge from inpatient rehabilitation.

Conclusion

This retrospective study's results provide external validation of previous findings, using a larger sample size. Following SCI, ventral tissue bridges hold significant predictive relationships with future pinprick sensory scores and dorsal tissue bridges hold significant predictive relationships with future light touch sensory scores.

Lateral Corticospinal Tract and Dorsal Column Damage: Predictive Relationships With Motor and Sensory Scores at Discharge From Acute Rehabilitation After Spinal Cord Injury

OBJECTIVE

To determine if lateral corticospinal tract (LCST) integrity demonstrates a significant predictive relationship with future ipsilateral lower extremity motor function (LEMS) and if dorsal column (DC) integrity demonstrates a significant predictive relationship with future light touch (LT) sensory function post spinal cord injury (SCI) at time of discharge from inpatient rehabilitation.

DESIGN

Retrospective analyses of imaging and clinical outcomes.

SETTING

University and academic hospital.

PARTICIPANTS

A total of 151 participants (N=151) with SCI.

INTERVENTIONS

Inpatient rehabilitation.

MAIN OUTCOME MEASURES

LEMS and LT scores at discharge from inpatient rehabilitation.

RESULTS

In 151 participants, right LCST spared tissue demonstrated a significant predictive relationship with right LEMS percentage recovered (β=0.56; 95% confidence interval [CI], 0.37-0.73; R=0.43; P<.001). Left LCST spared tissue demonstrated a significant predictive relationship with left LEMS percentage recovered (β=0.66; 95% CI, 0.50-0.82; R=0.51; P<.001). DC spared tissue demonstrated a significant predictive relationship with LT percentage recovered (β=0.69; 95% CI, 0.52-0.87; R=0.55; P<.001). When subgrouping the participants into motor complete vs incomplete SCI, motor relationships were no longer significant, but the sensory relationship remained significant. Those who had no voluntary motor function but recovered some also had significantly greater LCST spared tissue than those who did not recover motor function.

CONCLUSIONS

LCST demonstrated significant moderate predictive relationships with lower extremity motor function at the time of discharge from inpatient rehabilitation, in an ipsilesional manner. DC integrity demonstrated a significant moderate predictive relationship with recovered function of LT. With further development, these neuroimaging methods might be used to predict potential deficits after SCI and to provide corresponding targeted interventions.

Spinal cord pathology revealed by MRI in traumatic spinal cord injury

PURPOSE OF REVIEW

This review covers recent advances in identifying conventional and quantitative neuroimaging spinal cord biomarkers of lesion severity and remote spinal cord pathology following traumatic spinal cord injury (SCI). It discusses the potential of the most sensitive neuroimaging spinal cord biomarkers to complement clinical workup and improve prediction of recovery.

RECENT FINDINGS

At the injury site, preserved midsagittal tissue bridges - based on conventional sagittal T2-weighted scans - can be identified in the majority of SCI patients; its width being predictive of recovery. Remote from the injury, diffusion indices, and myelin/iron-sensitive neuroimaging-based changes are sensitive to secondary disease processes; its magnitude of change being associated with neurological outcome.

SUMMARY

Neuroimaging biomarkers reveal focal and remote cord pathology. These biomarkers show sensitivity to the underlying disease processes and are clinically eloquent. Thus, they improve injury characterization, enable spatiotemporal tracking of cord pathology, and predict recovery of function following traumatic SCI. Neuroimaging biomarkers, therefore, hold potential to complement the clinical diagnostic workup, improve patient stratification, and can serve as potential endpoints in clinical trials.

Longitudinal changes of spinal cord grey and white matter following spinal cord injury

OBJECTIVES

Traumatic and non-traumatic spinal cord injury produce neurodegeneration across the entire neuraxis. However, the spatiotemporal dynamics of spinal cord grey and white matter neurodegeneration above and below the injury is understudied.

METHODS

We acquired longitudinal data from 13 traumatic and 3 non-traumatic spinal cord injury patients (8-8 cervical and thoracic cord injuries) within 1.5 years after injury and 10 healthy controls over the same period. The protocol encompassed structural and diffusion-weighted MRI rostral (C2/C3) and caudal (lumbar enlargement) to the injury level to track tissue-specific neurodegeneration. Regression models assessed group differences in the temporal evolution of tissue-specific changes and associations with clinical outcomes.

RESULTS

At 2 months post-injury, white matter area was decreased by 8.5% and grey matter by 15.9% in the lumbar enlargement, while at C2/C3 only white matter was decreased (-9.7%). Patients had decreased cervical fractional anisotropy (FA: -11.3%) and increased radial diffusivity (+20.5%) in the dorsal column, while FA was lower in the lateral (-10.3%) and ventral columns (-9.7%) of the lumbar enlargement. White matter decreased by 0.34% and 0.35% per month at C2/C3 and lumbar enlargement, respectively, and grey matter decreased at C2/C3 by 0.70% per month.

CONCLUSIONS

This study describes the spatiotemporal dynamics of tissue-specific spinal cord neurodegeneration above and below a spinal cord injury. While above the injury, grey matter atrophy lagged initially behind white matter neurodegeneration, in the lumbar enlargement these processes progressed in parallel. Tracking trajectories of tissue-specific neurodegeneration provides valuable assessment tools for monitoring recovery and treatment effects.

Finger somatotopy is preserved after tetraplegia but deteriorates over time

Previous studies showed reorganised and/or altered activity in the primary sensorimotor cortex after a spinal cord injury (SCI), suggested to reflect abnormal processing. However, little is known about whether somatotopically specific representations can be activated despite reduced or absent afferent hand inputs. In this observational study, we used functional MRI and a (attempted) finger movement task in tetraplegic patients to characterise the somatotopic hand layout in primary somatosensory cortex. We further used structural MRI to assess spared spinal tissue bridges. We found that somatotopic hand representations can be activated through attempted finger movements in the absence of sensory and motor hand functioning, and no spared spinal tissue bridges. Such preserved hand somatotopy could be exploited by rehabilitation approaches that aim to establish new hand-brain functional connections after SCI (e.g. neuroprosthetics). However, over years since SCI the hand representation somatotopy deteriorated, suggesting that somatotopic hand representations are more easily targeted within the first years after SCI.

Potential of intraoperative ultrasonographic assessment of the spinal cord central echo complex in predicting postoperative neurological recovery of degenerative cervical myelopathy

BACKGROUND AND PURPOSE

The spinal cord central echo complex (SCCEC) is a special ultrasonography-based intramedullary structure, but its clinical significance in degenerative cervical myelopathy (DCM) is undefined. This study aimed to explore the potential of the SCCEC in predicting postoperative neurological recovery in DCM.

METHODS

Thirty-two DCM patients who underwent intraoperative ultrasonography-guided French-door laminoplasty were prospectively enrolled. The modified Japanese Orthopaedic Association (mJOA) score was evaluated preoperatively and 12 months postoperatively. SCCEC width (SCCEC-W), and anteroposterior diameter (APD) and transverse diameter (TD) of the spinal cord were measured on transverse ultrasonographic images, while the tissue widths from anterior and posterior borders of the spinal cord to the SCCEC were measured on sagittal ultrasonographic images. The APD of the spinal cord and occupying rate of the spinal canal were measured on preoperative magnetic resonance imaging (MRI).

RESULTS

All patients achieved improvements in mJOA scores, with an average recovery rate (RR) of 68.69 ± 20.22%. Spearman correlation analysis revealed that SCCEC-W, and ratios between the SCCEC-W and APD/TD based on ultrasonography, correlated moderately with mJOA score RR, with coefficients of -0.527, -0.605 and -0.514, respectively. The ratio between SCCEC-W and ultrasonographic TD correlated moderately with preoperative APD of the spinal cord. The MRI measurements and ultrasonography-based tissue widths showed no significant correlation with mJOA score RR.

CONCLUSIONS

The SCCEC may have predictive potential as an intraoperative indicator of neurological recovery in treating DCM. SCCEC-W may be related to spinal cord compression in DCM.

Improving Diagnostic Workup Following Traumatic Spinal Cord Injury: Advances in Biomarkers

PURPOSE OF REVIEW

Traumatic spinal cord injury (SCI) is a life-changing event with drastic implications for patients due to sensorimotor impairment and autonomous dysfunction. Current clinical evaluations focus on the assessment of injury level and severity using standardized neurological examinations. However, they fail to predict individual trajectories of recovery, which highlights the need for the development of advanced diagnostics. This narrative review identifies recent advances in the search of clinically relevant biomarkers in the field of SCI.

RECENT FINDINGS

Advanced neuroimaging and molecular biomarkers sensitive to the disease processes initiated by the SCI have been identified. These biomarkers range from advanced neuroimaging techniques, neurophysiological readouts, and molecular biomarkers identifying the concentrations of several proteins in blood and CSF samples. Some of these biomarkers improve current prediction models based on clinical readouts. Validation with larger patient cohorts is warranted. Several biomarkers have been identified-ranging from imaging to molecular markers-that could serve as advanced diagnostic and hence supplement current clinical assessments.

Distinct patterns of spasticity and corticospinal connectivity following complete spinal cord injury

KEY POINTS

Damage to corticospinal axons have implications for the development of spasticity following spinal cord injury (SCI). Here, we examined to which extent residual corticospinal connections and spasticity are present in muscles below the injury (quadriceps femoris and soleus) in humans with motor complete thoracic SCI. We found three distinct sub-groups of people: participants with spasticity and corticospinal responses in the quadriceps femoris and soleus, participants with spasticity and corticospinal responses in the quadriceps femoris only, and participants with no spasticity or corticospinal responses in either muscle. Spasticity and corticospinal responses were present in the quadriceps but never only in the soleus muscle, suggesting a proximal to distal gradient of symptoms of hyperreflexia. These results suggest that concomitant patterns of residual corticospinal connectivity and spasticity exist in humans with motor complete SCI and that a clinical exam of spasticity might be a good predictor of residual corticospinal connectivity.

ABSTRACT

The loss of corticospinal axons has implications for the development of spasticity following spinal cord injury (SCI). However, the extent to which residual corticospinal connections and spasticity are present across muscles below the injury remains unknown. To address this question, we tested spasticity using the Modified Ashworth Scale and transmission in the corticospinal pathway by examining motor evoked potentials elicited by transcranial magnetic stimulation over the leg motor cortex (cortical MEPs) and by direct activation of corticospinal axons by electrical stimulation over the thoracic spine (thoracic MEPs), in the quadriceps femoris and soleus muscles, in 30 individuals with motor complete thoracic SCI. Cortical MEPs were also conditioned by thoracic electrical stimulation at intervals allowing their summation or collision. We found three distinct sub-groups of participants: 47% showed spasticity in the quadriceps femoris and soleus muscle, 30% showed spasticity in the quadriceps femoris muscle only, and 23% showed no spasticity in either muscle. While cortical MEPs were present only in the quadriceps in participants with spasticity, thoracic MEPs were present in both muscles when spasticity was present. Thoracic electrical stimulation facilitated and suppressed cortical MEPs, showing that both forms of stimulation activated similar corticospinal axons. Cortical and thoracic MEPs correlated with the degree of spasticity in both muscles. These results provide the first evidence that related patterns of residual corticospinal connectivity and spasticity exist in muscles below the injury after motor complete thoracic SCI and highlight that a clinical exam of spasticity can predict residual corticospinal connectivity after severe paralysis. This article is protected by copyright. All rights reserved.

The influence of conventional T2 MRI indices in predicting who will walk outside one year after spinal cord injury

CONTEXT/OBJECTIVE

Magnetic resonance imaging (MRI) indices of spinal cord damage are predictive of future motor function after spinal cord injury (SCI): hyperintensity length, midsagittal tissue bridges, and Brain and Spinal Injury Center (BASIC) scores. Whether these indices are predictive of outdoor walking after SCI is unknown. The primary purpose was to see if these MRI indices predict the ability to walk outdoors one-year after SCI. The secondary purpose was to determine if MRI indices provide additional predictive value if initial lower extremity motor scores are available.

DESIGN

Retrospective. Clinical T₂-weighted MRIs were used to quantify spinal cord damage. Three MRI indices were calculated: midsagittal ventral tissue bridges, hyperintensity length, BASIC scores.

SETTING

Academic hospital.

PARTICIPANTS

129 participants with cervical SCI.

INTERVENTIONS

Inpatient rehabilitation.

OUTCOMES MEASURES

One year after SCI, participants self-reported their outdoor walking ability.

RESULTS

Midsagittal ventral tissue bridges, hyperintensity length, and BASIC scores significantly correlated with outdoor walking ability (R = 0.34, P < 0.001; R = -0.25, P < 0.01; Rs = -0.35, P < 001, respectively). Using midsagittal ventral tissue bridges and hyperintensity length, the final adjusted R² for model 1 = 0.19. For model 2, the adjusted R² using motor scores alone = 0.81 and MRI variables were non-significant. All five participants with observable intramedullary hemorrhage reported they were unable to walk one block outdoors.

CONCLUSIONS

The MRI indices were significant predictors of outdoor walking ability, but when motor scores were available, this was the strongest predictor and neither midsagittal tissue bridges nor hyperintensity length contributed additional value. MRI indices may be a quick and convenient supplement to physical examination when motor testing is unavailable.

Intensity of Intraoperative Spinal Cord Hyperechogenicity as a Novel Potential Predictive Indicator of Neurological Recovery for Degenerative Cervical Myelopathy

OBJECTIVE

To analyze the correlations between intraoperative ultrasound and MRI metrics of the spinal cord in degenerative cervical myelopathy and identify novel potential predictive ultrasonic indicators of neurological recovery for degenerative cervical myelopathy.

MATERIALS AND METHODS

Twenty-two patients who underwent French-door laminoplasty for multilevel degenerative cervical myelopathy were followed up for 12 months. The Japanese Orthopedic Association (JOA) scores were assessed preoperatively and 12 months postoperatively. Maximum spinal cord compression and compression rates were measured and calculated using both intraoperative ultrasound imaging and preoperative T2-weight (T2W) MRI. Signal change rates of the spinal cord on preoperative T2W MRI and gray value ratios of dorsal and ventral spinal cord hyperechogenicity on intraoperative ultrasound imaging were measured and calculated. Correlations between intraoperative ultrasound metrics, MRI metrics, and the recovery rate JOA scores were analyzed using Spearman correlation analysis.

RESULTS

The postoperative JOA scores improved significantly, with a mean recovery rate of 65.0 ± 20.3% (p < 0.001). No significant correlations were found between the operative ultrasound metrics and MRI metrics. The gray value ratios of the spinal cord hyperechogenicity was negatively correlated with the recovery rate of JOA scores (ρ = -0.638, p = 0.001), while the ventral and dorsal gray value ratios of spinal cord hyperechogenicity were negatively correlated with the recovery rate of JOA-motor scores (ρ = -0.582, p = 0.004) and JOA-sensory scores (ρ = -0.452, p = 0.035), respectively. The dorsal gray value ratio was significantly higher than the ventral gray value ratio (p < 0.001), while the recovery rate of JOA-motor scores was better than that of JOA-sensory scores at 12 months post-surgery (p = 0.028).

CONCLUSION

For degenerative cervical myelopathy, the correlations between intraoperative ultrasound and preoperative T2W MRI metrics were not significant. Gray value ratios of the spinal cord hyperechogenicity and dorsal and ventral spinal cord hyperechogenicity were significantly correlated with neurological recovery at 12 months postoperatively.

Neurophysiological Changes in the First Year After Cell Transplantation in Sub-acute Complete Paraplegia

Neurophysiological testing can provide quantitative information about motor, sensory, and autonomic system connectivity following spinal cord injury (SCI). The clinical examination may be insufficiently sensitive and specific to reveal evolving changes in neural circuits after severe injury. Neurophysiologic data may provide otherwise imperceptible circuit information that has rarely been acquired in biologics clinical trials in SCI. We reported a Phase 1 study of autologous purified Schwann cell suspension transplantation into the injury epicenter of participants with complete subacute thoracic SCI, observing no clinical improvements. Here, we report longitudinal electrophysiological assessments conducted during the trial. Six participants underwent neurophysiology screening pre-transplantation with three post-transplantation neurophysiological assessments, focused on the thoracoabdominal region and lower limbs, including MEPs, SSEPs, voluntarily triggered EMG, and changes in GSR. We found several notable signals not detectable by clinical exam. In all six participants, thoracoabdominal motor connectivity was detected below the clinically assigned neurological level defined by sensory preservation. Additionally, small voluntary activations of leg and foot muscles or positive lower extremity MEPs were detected in all participants. Voluntary EMG was most sensitive to detect leg motor function. The recorded MEP amplitudes and latencies indicated a more caudal thoracic level above which amplitude recovery over time was observed. In contrast, further below, amplitudes showed less improvement, and latencies were increased. Intercostal spasms observed with EMG may also indicate this thoracic “motor level.” Galvanic skin testing revealed autonomic dysfunction in the hands above the injury levels. As an open-label study, we can establish no clear link between these observations and cell transplantation. This neurophysiological characterization may be of value to detect therapeutic effects in future controlled studies.

The neuroanatomical-functional paradox in spinal cord injury

Although lesion size is widely considered to be the most reliable predictor of outcome after CNS injury, lesions of comparable size can produce vastly different magnitudes of functional impairment and subsequent recovery. This neuroanatomical-functional paradox is likely to contribute to the many failed attempts to independently replicate findings from animal models of neurotrauma. In humans, the analogous clinical-radiological paradox could explain why individuals with similar injuries can respond differently to rehabilitation. We describe the neuroanatomical-functional paradox in the context of traumatic spinal cord injury (SCI) and discuss the underlying mechanisms of the paradox, including the concepts of lesion-affected and recovery-related networks. We also consider the various secondary complications that further limit the accuracy of outcome prediction in SCI and provide suggestions for how to increase the predictive, translational value of preclinical SCI models.

Predictive Value of Midsagittal Tissue Bridges on Functional Recovery After Spinal Cord Injury

Background

The majority of patients with spinal cord injury (SCI) have anatomically incomplete lesions and present with preserved tissue bridges, yet their outcomes vary.

Objective

To assess the predictive value of the anatomical location (ventral/dorsal) and width of preserved midsagittal tissue bridges for American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade conversion and SCI patient stratification into recovery-specific subgroups.

Methods

This retrospective longitudinal study includes 70 patients (56 men, age: 52.36 ± 18.58 years) with subacute (ie, 1 month) SCI (45 tetraplegics, 25 paraplegics), 1-month neuroimaging data, and 1-month and 12-month clinical data. One-month midsagittal T2-weighted scans were used to determine the location and width of tissue bridges. Their associations with functional outcomes were assessed using partial correlation and unbiased recursive partitioning conditional inference tree (URP-CTREE).

Results

Fifty-seven (81.4%) of 70 patients had tissue bridges (2.53 ± 2.04 mm) at 1-month post-SCI. Larger ventral (P = .001, r = 0.511) and dorsal (P < .001, r = 0.546) tissue bridges were associated with higher AIS conversion rates 12 months post-SCI (n = 39). URP-CTREE analysis identified 1-month ventral tissue bridges as predictors of 12-month total motor scores (0.4 mm cutoff, P = .008), recovery of upper extremity motor scores at 12 months (1.82 mm cutoff, P = .002), 12-month pin-prick scores (1.4 mm cutoff, P = .018), and dorsal tissue bridges at 1 month as predictors of 12-month Spinal Cord Independence Measure scores (0.5 mm cutoff, P = .003).

Conclusions

Midsagittal tissue bridges add predictive value to baseline clinical measures for post-SCI recovery. Based on tissue bridges’ width, patients can be classified into subgroups of clinical recovery profiles. Midsagittal tissue bridges provide means to optimize patient stratification in clinical trials.

Spinal Cord Imaging Markers and Recovery of Volitional Leg Movement With Spinal Cord Epidural Stimulation in Individuals With Clinically Motor Complete Spinal Cord Injury

Previous studies have shown that epidural stimulation of the lumbosacral spinal cord (scES) can re-enable lower limb volitional motor control in individuals with chronic, clinically motor complete spinal cord injury (SCI). This observation entails that residual supraspinal connectivity to the lumbosacral spinal circuitry still persisted after SCI, although it was non-detectable when scES was not provided. In the present study, we aimed at exploring further the mechanisms underlying scES-promoted recovery of volitional lower limb motor control by investigating neuroimaging markers at the spinal cord lesion site via magnetic resonance imaging (MRI). Spinal cord MRI was collected prior to epidural stimulator implantation in 13 individuals with chronic, clinically motor complete SCI, and the spared tissue of specific regions of the spinal cord (anterior, posterior, right, left, and total cord) was assessed. After epidural stimulator implantation, and prior to any training, volitional motor control was evaluated during left and right lower limb flexion and ankle dorsiflexion attempts. The ability to generate force exertion and movement was not correlated to any neuroimaging marker. On the other hand, spared tissue of specific cord regions significantly and importantly correlated with some aspects of motor control that include activation amplitude of antagonist (negative correlation) muscles during left ankle dorsiflexion, and electromyographic coordination patterns during right lower limb flexion. The fact that amount and location of spared spinal cord tissue at the lesion site were not related to the ability to generate volitional lower limb movements may suggest that supraspinal inputs through spared spinal cord regions that differ across individuals can result in the generation of lower limb volitional motor output prior to any training when epidural stimulation is provided.

Tissue bridges predict neuropathic pain emergence after spinal cord injury

OBJECTIVE

To assess associations between preserved spinal cord tissue quantified by the width of ventral and dorsal tissue bridges and neuropathic pain development after spinal cord injury.

METHODS

This retrospective longitudinal study includes 44 patients (35 men; mean (SD) age, 50.05 (18.88) years) with subacute (ie, 1 month) spinal cord injury (25 patients with neuropathic pain, 19 pain-free patients) and neuroimaging data who had a follow-up clinical assessment at 12 months. Widths of tissue bridges were calculated from midsagittal T2-weighted images and compared across groups. Regression analyses were used to identify relationships between these neuroimaging measures and previously assessed pain intensity and pin-prick score.

RESULTS

Pin-prick score of the 25 patients with neuropathic pain increased from 1 to 12 months (Δmean=10.08, 95% CI 2.66 to 17.50, p=0.010), while it stayed similar in pain-free patients (Δmean=2.74, 95% CI -7.36 to 12.84, p=0.576). They also had larger ventral tissue bridges (Δmedian=0.80, 95% CI 0.20 to 1.71, p=0.008) at 1 month when compared with pain-free patients. Conditional inference tree analysis revealed that ventral tissue bridges' width (≤2.1 or >2.1 mm) at 1 month is the strongest predictor for 12 months neuropathic pain intensity (1.90±2.26 and 3.83±1.19, p=0.042) and 12 months pin-prick score (63.84±28.26 and 92.67±19.43, p=0.025).

INTERPRETATION

Larger width of ventral tissue bridges-a proxy for spinothalamic tract function-at 1 month post-spinal cord injury is associated with the emergence and maintenance of neuropathic pain and increased pin-prick sensation. Spared ventral tissue bridges could serve as neuroimaging biomarkers of neuropathic pain and might be used for prediction and monitoring of pain outcomes and stratification of patients in interventional trials.

Traumatic and nontraumatic spinal cord injury: pathological insights from neuroimaging

Pathophysiological changes in the spinal cord white and grey matter resulting from injury can be observed with MRI techniques. These techniques provide sensitive markers of macrostructural and microstructural tissue integrity, which correlate with histological findings. Spinal cord MRI findings in traumatic spinal cord injury (tSCI) and nontraumatic spinal cord injury - the most common form of which is degenerative cervical myelopathy (DCM) - have provided important insights into the pathophysiological processes taking place not just at the focal injury site but also rostral and caudal to the spinal injury. Although tSCI and DCM have different aetiologies, they show similar degrees of spinal cord pathology remote from the injury site, suggesting the involvement of similar secondary degenerative mechanisms. Advanced quantitative MRI protocols that are sensitive to spinal cord pathology have the potential to improve diagnosis and, more importantly, predict outcomes in patients with tSCI or nontraumatic spinal cord injury. This Review describes the insights into tSCI and DCM that have been revealed by neuroimaging and outlines current activities and future directions for the field.

Guidelines for the conduct of clinical trials in spinal cord injury: Neuroimaging biomarkers

Traumatic spinal cord injury (SCI) leads to immediate neuronal and axonal damage at the focal injury site and triggers secondary pathologic series of events resulting in sensorimotor and autonomic dysfunction below the level of injury. Although there is no cure for SCI, neuroprotective and regenerative therapies show promising results at the preclinical stage. There is a pressing need to develop non-invasive outcome measures that can indicate whether a candidate therapeutic agent or a cocktail of therapeutic agents are positively altering the underlying disease processes. Recent conventional MRI studies have quantified spinal cord lesion characteristics and elucidated their relationship between severity of injury to clinical impairment and recovery. Next to the quantification of the primary cord damage, quantitative MRI measures of spinal cord (rostrocaudally to the lesion site) and brain integrity have demonstrated progressive and specific neurodegeneration of afferent and efferent neuronal pathways. MRI could therefore play a key role to ultimately uncover the relationship between clinical impairment/recovery and injury-induced neurodegenerative changes in the spinal cord and brain. Moreover, neuroimaging biomarkers hold promises to improve clinical trial design and efficiency through better patient stratification. The purpose of this narrative review is therefore to propose a guideline of clinically available MRI sequences and their derived neuroimaging biomarkers that have the potential to assess tissue damage at the macro- and microstructural level after SCI. In this piece, we make a recommendation for the use of key MRI sequences-both conventional and advanced-for clinical work-up and clinical trials.