Visibility Graph Analysis of Intraspinal Pressure Signal Predicts Functional Outcome in Spinal Cord Injured Patients

Guidelines for neuroprognostication in adults with traumatic spinal cord injury

BACKGROUND

Traumatic spinal cord injury (tSCI) impacts patients and their families acutely and often for the long term. The ability of clinicians to share prognostic information about mortality and functional outcomes allows patients and their surrogates to engage in decision-making and plan for the future. These guidelines provide recommendations on the reliability of acute-phase clinical predictors to inform neuroprognostication and guide clinicians in counseling adult patients with tSCI or their surrogates.

METHODS

A narrative systematic review was completed using Grading of Recommendations Assessment, Development, and Evaluation methodology. Candidate predictors, including clinical variables and prediction models, were selected based on clinical relevance and presence of an appropriate body of evidence. The Population/Intervention/Comparator/Outcome/Timing/Setting question was framed as "When counseling patients or surrogates of critically ill patients with traumatic spinal cord injury, should < predictor, with time of assessment if appropriate > be considered a reliable predictor of < outcome, with time frame of assessment >?" Additional full-text screening criteria were used to exclude small and lower quality studies. Following construction of an evidence profile and summary of findings, recommendations were based on four Grading of Recommendations Assessment, Development, and Evaluation criteria: quality of evidence, balance of desirable and undesirable consequences, values and preferences, and resource use. Good practice recommendations addressed essential principles of neuroprognostication that could not be framed in the Population/Intervention/Comparator/Outcome/Timing/Setting format. Throughout the guideline development process, an individual living with tSCI provided perspective on patient-centered priorities.

RESULTS

Six candidate clinical variables and one prediction model were selected. Out of 11,132 articles screened, 369 met inclusion criteria for full-text review and 35 articles met eligibility criteria to guide recommendations. We recommend pathologic findings on magnetic resonance imaging, neurological level of injury, and severity of injury as moderately reliable predictors of American Spinal Cord Injury Impairment Scale improvement and the Dutch Clinical Prediction Rule as a moderately reliable prediction model of independent ambulation at 1 year after injury. No other reliable or moderately reliable predictors of mortality or functional outcome were identified. Good practice recommendations include considering the complete clinical condition as opposed to a single variable and communicating the challenges of likely functional deficits as well as potential for improvement and for long-term quality of life with SCI-related deficits to patients and surrogates.

CONCLUSIONS

These guidelines provide recommendations about the reliability of acute-phase predictors of mortality, functional outcome, American Spinal Injury Association Impairment Scale grade conversion, and recovery of independent ambulation for consideration when counseling patients with tSCI or their surrogates and suggest broad principles of neuroprognostication in this context.

Photoplethysmography-based cuffless blood pressure estimation: an image encoding and fusion approach

Objective.Photoplethysmography (PPG) is a promising wearable technology that detects volumetric changes in microcirculation using a light source and a sensor on the skin's surface. PPG has been shown to be useful for non-invasive blood pressure (BP) measurement. Deep learning-based BP measurements are now gaining popularity. However, almost all methods focus on 1D PPG. We aimed to design an end-to-end approach for estimating BP using image encodings from a 2D perspective.Approach.In this paper, we present a BP estimation approach based on an image encoding and fusion (BP-IEF) technique. We convert the PPG into five image encodings and use them as input. The proposed BP-IEF consists of two parts: an encoder and a decoder. In addition, three kinds of well-known neural networks are taken as the fundamental architecture of the encoder. The decoder is a hybrid architecture that consists of convolutional and fully connected layers, which are used to fuse features from the encoder.Main results.The performance of the proposed BP-IEF is evaluated on the UCI database in both non-mixed and mixed manners. On the non-mixed dataset, the root mean square error and mean absolute error for systolic BP (SBP) are 13.031 mmHg and 9.187 mmHg respectively, while for diastolic BP (DBP) they are 5.049 mmHg and 3.810 mmHg. On the mixed dataset, the corresponding values for SBP are 4.623 mmHg and 3.058 mmHg, while for DBP the values are 2.350 mmHg and 1.608 mmHg. In addition, both SBP and DBP estimation on the mixed dataset achieved grade A compared to the British Hypertension Society standard. The DBP estimation on the non-mixed dataset also achieved grade A.Significance.The results indicate that the proposed approach has the potential to improve on the current mobile healthcare for cuffless BP measurement.

Proposal of a Management Algorithm to Predict the Need for Expansion Duraplasty in American Spinal Injury Association Impairment Scale Grades A-C Traumatic Cervical Spinal Cord Injury Patients

Expansion duraplasty to reopen effaced subarachnoid space and improve spinal cord perfusion, autoregulation, and spinal pressure reactivity index (sPRX) has been advocated in patients with traumatic cervical spinal cord injury (tCSCI). We designed this study to identify candidates for expansion duraplasty, based on the absence of cerebrospinal fluid (CSF) interface around the spinal cord on magnetic resonance imaging (MRI), in the setting of otherwise adequate bony decompression. Over a 61-month period, 104 consecutive American Spinal Injury Association Impairment Scale (AIS) grades A-C patients with tCSCI had post-operative MRI to assess the adequacy of surgical decompression. Their mean age was 53.4 years, and 89% were male. Sixty-one patients had falls, 31 motor vehicle collisions, 11 sport injuries, and one an assault. The AIS grade was A in 56, B in 18, and C in 30 patients. Fifty-four patients had fracture dislocations; there was no evidence of skeletal injury in 50 patients. Mean intramedullary lesion length (IMLL) was 46.9 (standard deviation = 19.4) mm. Median time from injury to decompression was 17 h (interquartile range 15.2 h). After surgery, 94 patients had adequate decompression as judged by the presence of CSF anterior and posterior to the spinal cord, whereas 10 patients had effacement of the subarachnoid space at the injury epicenter. In two patients whose decompression was not definitive and post-operative MRI indicated inadequate decompression, expansion duraplasty was performed. Candidates for expansion duraplasty (i.e., those with inadequate decompression) were significantly younger (p < 0.0001), were AIS grade A (p < 0.0016), had either sport injuries (six patients) or motor vehicle collisions (three patients) (p < 0.0001), had fracture dislocation (p = 0.00016), and had longer IMLL (p = 0.0097). In regression models, patients with sport injuries and inadequate decompression were suitable candidates for expansion duraplasty (p = 0.03). Further, 9.6% of patients failed bony decompression alone and either did (2) or would have (8) benefited from expansion duraplasty.

Multimodal interventions to optimize spinal cord perfusion in patients with acute traumatic spinal cord injuries: a systematic review

OBJECTIVE

The authors systematically reviewed current evidence for the utility of mean arterial pressure (MAP), intraspinal pressure (ISP), and spinal cord perfusion pressure (SCPP) as predictors of outcomes after traumatic spinal cord injury (SCI).

METHODS

PubMed, Cochrane Reviews Library, EMBASE, and Scopus databases were queried in December 2020. Two independent reviewers screened articles using Covidence software. Disagreements were resolved by a third reviewer. The inclusion criteria for articles were 1) available in English; 2) full text; 3) clinical studies on traumatic SCI interventions; 4) involved only human participants; and 5) focused on MAP, ISP, or SCPP. Exclusion criteria were 1) only available in non-English languages; 2) focused only on the brain; 3) described spinal diseases other than SCI; 4) interventions altering parameters other than MAP, ISP, or SCPP; and 5) animal studies. Studies were analyzed qualitatively and grouped into two categories: interventions increasing MAP or interventions decreasing ISP. The Scottish Intercollegiate Guidelines Network level of evidence was used to assess bias and the Grading of Recommendations, Assessment, Development, and Evaluation approach was used to rate confidence in the anticipated effects of each outcome.

RESULTS

A total of 2540 unique articles were identified, of which 72 proceeded to full-text review and 24 were included in analysis. One additional study was included retrospectively. Articles that went through full-text review were excluded if they were a review paper (n = 12), not a full article (n = 12), a duplicate paper (n = 9), not a human study (n = 3), not in English (n = 3), not pertaining to traumatic SCI (n = 3), an improper intervention (n = 3), without intervention (n = 2), and without analysis of intervention (n = 1). Although maintaining optimal MAP levels is the current recommendation for SCI management, the published literature supports maintenance of SCPP as a stronger indicator of favorable outcomes. Studies also suggest that laminectomy and durotomy may provide better outcomes than laminectomy alone, although higher-level studies are needed. Current evidence is inconclusive on the effectiveness of CSF drainage for reducing ISP.

CONCLUSIONS

This review demonstrates the importance of assessing how different interventions may vary in their ability to optimize SCPP.

Significance of spinal cord perfusion pressure following spinal cord injury: A systematic scoping review

This scoping review systematically reviewed relevant research to summarize the literature addressing the significance of monitoring spinal cord perfusion pressure (SCPP) in acute traumatic spinal cord injury (SCI). The objectives of the review were to (1) examine the nature of research in the field of SCPP monitoring in SCI, (2) summarize the key research findings in the field, and (3) identify research gaps in the existing literature and future research priorities. Primary literature searches were conducted using databases (Medline and Embase) and expanded searches were conducted by reviewing the references of eligible articles and searches of Scopus, Web of Science core collection, Google Scholar, and conference abstracts. Relevant data were extracted from the studies and synthesis of findings was guided by the identification of patterns across studies to identify key themes and research gaps within the literature. Following primary and expanded searches, a total of 883 articles were screened. Seventy-three articles met the review inclusion criteria, including 34 original research articles. Other articles were categorized as conference abstracts, literature reviews, systematic reviews, letters to the editor, perspective articles, and editorials. Key themes relevant to the research question that emerged from the review included the relationship between SCPP and neurological recovery, the safety of monitoring pressures within the intrathecal space, and methods of intervention to enhance SCPP in the setting of acute traumatic SCI. Original research that aims to enhance SCPP by targeting increases in mean arterial pressure or reducing pressure in the intrathecal space is reviewed. Further discussion regarding where pressure within the intrathecal space should be measured is provided. Finally, we highlight research gaps in the literature such as determining the feasibility of invasive monitoring at smaller centers, the need for a better understanding of cerebrospinal fluid physiology following SCI, and novel pharmacological interventions to enhance SCPP in the setting of acute traumatic SCI. Ultimately, despite a growing body of literature on the significance of SCPP monitoring following SCI, there are still a number of important knowledge gaps that will require further investigation.

Advances in monitoring for acute spinal cord injury: a narrative review of current literature

Spinal cord injury (SCI) is a devastating condition that affects about 17,000 individuals every year in the United States, with approximately 294,000 people living with the ramifications of the initial injury. After the initial primary injury, SCI has a secondary phase during which the spinal cord sustains further injury due to ischemia, excitotoxicity, immune-mediated damage, mitochondrial dysfunction, apoptosis, and oxidative stress. The multifaceted injury progression process requires a sophisticated injury-monitoring technique for an accurate assessment of SCI patients. In this narrative review, we discuss SCI monitoring modalities, including pressure probes and catheters, micro dialysis, electrophysiologic measures, biomarkers, and imaging studies. The optimal next-generation injury monitoring setup should include multiple modalities and should integrate the data to produce a final simplified assessment of the injury and determine markers of intervention to improve patient outcomes.

Individual-specific networks for prediction modelling – A scoping review of methods

Background

Recent advances in biotechnology enable the acquisition of high-dimensional data on individuals, posing challenges for prediction models which traditionally use covariates such as clinical patient characteristics. Alternative forms of covariate representations for the features derived from these modern data modalities should be considered that can utilize their intrinsic interconnection. The connectivity information between these features can be represented as an individual-specific network defined by a set of nodes and edges, the strength of which can vary from individual to individual. Global or local graph-theoretical features describing the network may constitute potential prognostic biomarkers instead of or in addition to traditional covariates and may replace the often unsuccessful search for individual biomarkers in a high-dimensional predictor space.

Methods

We conducted a scoping review to identify, collate and critically appraise the state-of-art in the use of individual-specific networks for prediction modelling in medicine and applied health research, published during 2000–2020 in the electronic databases PubMed, Scopus and Embase.

Results

Our scoping review revealed the main application areas namely neurology and pathopsychology, followed by cancer research, cardiology and pathology (N = 148). Network construction was mainly based on Pearson correlation coefficients of repeated measurements, but also alternative approaches (e.g. partial correlation, visibility graphs) were found. For covariates measured only once per individual, network construction was mostly based on quantifying an individual’s contribution to the overall group-level structure. Despite the multitude of identified methodological approaches for individual-specific network inference, the number of studies that were intended to enable the prediction of clinical outcomes for future individuals was quite limited, and most of the models served as proof of concept that network characteristics can in principle be useful for prediction.

Conclusion

The current body of research clearly demonstrates the value of individual-specific network analysis for prediction modelling, but it has not yet been considered as a general tool outside the current areas of application. More methodological research is still needed on well-founded strategies for network inference, especially on adequate network sparsification and outcome-guided graph-theoretical feature extraction and selection, and on how networks can be exploited efficiently for prediction modelling.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01544-6.

Medical Communication Services after Traumatic Spinal Cord Injury

It is difficult to assess and monitor the spinal cord injury (SCI) because of its pathophysiology after injury, with different degrees of prognosis and various treatment methods, including laminectomy, durotomy, and myelotomy. Medical communication services with different factors such as time of surgical intervention, procedure choice, spinal cord perfusion pressure (SCPP), and intraspinal pressure (ISP) contribute a significant role in improving neurological outcomes. This review aims to show the benefits of communication services and factors such as ISP, SCPP, and surgical intervention time in order to achieve positive long-term outcomes after an appropriate treatment method in SCI patients. The SCPP was found between 90 and 100 mmHg for the best outcome, MAP was found between 110 and 130 mmHg, and mean ISP is ≤20 mmHg after injury. Laminectomy alone cannot reduce the pressure between the dura and swollen cord. Durotomy and duroplasty considered as treatment choices after severe traumatic spinal cord injury (TSCI).

Acute, Severe Traumatic Spinal Cord Injury: Monitoring from the Injury Site and Expansion Duraplasty

We discuss 2 evolving management options for acute spinal cord injury that hold promise to further improve outcome: pressure monitoring from the injured cord and expansion duraplasty. Probes surgically implanted at the injury site can transduce intraspinal pressure, spinal cord perfusion pressure, and cord metabolism. Intraspinal pressure is not adequately reduced by bony decompression alone because the swollen, injured cord is compressed against the dura. Expansion duraplasty may be necessary to effectively decompress the injured cord. A randomized controlled trial called DISCUS is investigating expansion duraplasty as a novel treatment for acute, severe traumatic cervical spinal cord injury.

Characterizing cardiorespiratory interaction in preterm infants across sleep states using visibility graph analysis

Cardiorespiratory interaction (CRI) has been intensively studied in adult sleep, yet not in preterm infants, in particular across different sleep states including wake (W), active sleep (AS), and quiet sleep (QS). The aim of this study was to quantify the interaction between cardiac and respiratory activities in different sleep states of preterm infants. The postmenstrual age (PMA) of preterm infants was also taken into consideration. The CRI during sleep was analyzed using a visibility graph (VG) method, enabling the nonlinear analysis of CRI in a complex network. For each sleep state, parameters quantifying various aspects of the CRI characteristics from constructed VG network including mean degree (D_m) and its variability (D_sd), clustering coefficient (CC_m) and its variability (CC_sd), assortativity coefficient (AC), and complexity (D_SE) were extracted from the CRI networks. The interaction effect of sleep state and PMA was found to be statistically significant on all CRI parameters except for AC and D_SE. The main effect between sleep state and CRI parameters was statistically significant except for CC_m, and that between PMA and CRI parameters was statistically significant except for D_SE. In conclusion, the CRI of preterm infants is associated with sleep states and PMA in general. For preterm infants with a larger PMA, CRI has a more clustered pattern during different sleep states, where QS shows a more regular, stratified, and stronger CRI than other states. In the future, these parameters can be potentially used to separate sleep states in preterm infants.NEW & NOTEWORTHY The interaction between cardiac and respiratory activities is investigated in preterm infant sleep using an advanced nonlinear method (visibility graph) and some important characteristics are shown to be significantly different across sleep states, which has not been studied before.

Effect of Durotomy versus Myelotomy on Tissue Sparing and Functional Outcome after Spinal Cord Injury

Various surgical strategies have been developed to alleviate elevated intraspinal pressure (ISP) following acute traumatic spinal cord injury (tSCI). Surgical decompression of either the dural (durotomy) or the dural and pial (myelotomy) lining of the spinal cord has been proposed. However, a direct comparison of these two strategies is lacking. Here, we compare the histological and functional effects of durotomy alone and durotomy plus myelotomy in a rodent model of acute thoracic tSCI. Our results indicate that tSCI causes local tissue edema and significantly elevates ISP (7.4 ± 0.3 mmHg) compared with physiological ISP (1.7 ± 0.4 mmHg; p < 0.001). Both durotomy alone and durotomy plus myelotomy effectively mitigate elevated local ISP (p < 0.001). Histological examination at 10 weeks after tSCI revealed that durotomy plus myelotomy promoted spinal tissue sparing by 13.7% compared with durotomy alone, and by 25.9% compared with tSCI-only (p < 0.0001). Both types of decompression surgeries elicited a significant beneficial impact on gray matter sparing (p < 0.01). Impressively, durotomy plus myelotomy surgery increased preservation of motor neurons by 174.3% compared with tSCI-only (p < 0.05). Durotomy plus myelotomy surgery also significantly promoted recovery of hindlimb locomotor function in an open-field test (p < 0.001). Interestingly, only durotomy alone resulted in favorable recovery of bladder and Ladder Walk performance. Combined, our data suggest that durotomy plus myelotomy following acute tSCI facilitates tissue sparing and recovery of locomotor function. In the future, biomarkers identifying spinal cord injuries that can benefit from either durotomy alone or durotomy plus myelotomy need to be developed.

Extended durotomy to treat severe spinal cord injury after acute thoracolumbar disc herniation in dogs

OBJECTIVE

To report recovery of ambulation of dogs treated with extended thoracolumbar durotomy for severe spinal cord injury caused by intervertebral disc herniation.

STUDY DESIGN

Descriptive cohort.

ANIMALS

Twenty-six consecutive paraplegic dogs presented with loss of deep pain sensation after acute thoracolumbar intervertebral disc herniation.

METHODS

Each dog underwent routine diagnostic assessment and surgery for removal of extradural herniated intervertebral disc, followed by a four-vertebral body length durotomy centered on the herniated disc. Each dog was followed up until it was able to walk 10 steps without assistance or until 6 months after surgery.

RESULTS

Sixteen of 26 dogs recovered to walk unaided (all but one also recovered fecal and urinary continence), and six dogs did not; four dogs were lost to follow-up. One dog was euthanized because of signs consistent with progressive myelomalacia. There was no evidence of detrimental effects of durotomy within the period of study. Using Bayesian analysis, we found a point estimate of successful outcome of 71% with 95% credible interval from 52% to 87%.

CONCLUSION

Extended durotomy seemed to improve the outcome of dogs in our case series without increase in morbidity.

CLINICAL SIGNIFICANCE

Extended durotomy appears safe and may improve the outcome of dogs with severe thoracolumbar mixed contusion and compressive injuries associated with acute intervertebral disc extrusion.

Efficacy of Ultra-Early (< 12 h), Early (12-24 h), and Late (>24-138.5 h) Surgery with Magnetic Resonance Imaging-Confirmed Decompression in American Spinal Injury Association Impairment Scale Grades A, B, and C Cervical Spinal Cord Injury

In cervical traumatic spinal cord injury (TSCI), the therapeutic effect of timing of surgery on neurological recovery remains uncertain. Additionally, the relationship between extent of decompression, imaging biomarker evidence of injury severity, and outcome is incompletely understood. We investigated the effect of timing of decompression on long-term neurological outcome in patients with complete spinal cord decompression confirmed on postoperative magnetic resonance imaging (MRI). American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade conversion was determined in 72 AIS grades A, B, and C patients 6 months after confirmed decompression. Thirty-two patients underwent decompressive surgery ultra-early (< 12 h), 25 underwent decompressive surgery early (12-24 h), and 15 underwent decompressive surgery late (> 24-138.5 h) after injury. Age, gender, injury mechanism, intramedullary lesion length (IMLL) on MRI, admission ASIA motor score, and surgical technique were not statistically different among groups. Motor complete patients (p = 0.009) and those with fracture dislocations (p = 0.01) tended to be operated on earlier. Improvement of one grade or more was present in 55.6% of AIS grade A, 60.9% of AIS grade B, and 86.4% of AIS grade C patients. Admission AIS motor score (p = 0.0004) and pre-operative IMLL (p = 0.00001) were the strongest predictors of neurological outcome. AIS grade improvement occurred in 65.6%, 60%, and 80% of patients who underwent decompression ultra-early, early, and late, respectively (p = 0.424). Multiple regression analysis revealed that IMLL was the only significant variable predictive of AIS grade conversion to a better grade (odds ratio, 0.908; confidence interval [CI], 0.862-0.957; p < 0.001). We conclude that in patients with post-operative MRI confirmation of complete decompression following cervical TSCI, pre-operative IMLL, not the timing of surgery, determines long-term neurological outcome.