Serum albumin as a predictor of neurological recovery after spinal cord injury: a replication study

STUDY DESIGN

This was a secondary analysis on an observational cohort study.

OBJECTIVE

To determine if serum albumin significantly associates with long-term neurological outcome (i.e., 1-year post-injury) in a contemporary cohort of individuals with spinal cord injury.

SETTING

Six rehabilitation centers across the United States.

METHODS

A secondary analysis of neurological outcomes and serum albumin concentrations was performed on data from the Spinal Cord Injury Rehabilitation study. Data was accessed from the Archive of Data on Disability to Enable Policy and research (ADDEP). The primary analysis applied unbiased recursive partitioning to examine the relationship between serum albumin, injury severity, and long-term outcomes. The analysis is accessible via https://rpubs.com/AnhKhoaVo/586028 .

RESULTS

Serum albumin concentration was significantly associated with lower extremity motor scores (LEMS) and American Spinal Injury Association Impairment Scale (AIS) grade at admission to rehabilitation. Serum albumin concentrations alone were also significantly associated with change of LEMS and marked recovery (improvement of at least 2 AIS grades and/or recovery to walking) at 1-year post injury. However, after adjusting for admission to rehabilitation LEMS and AIS grade, serum albumin was not significant.

CONCLUSION

The current study partially confirms our previous observations that serum albumin concentrations are associated with neurological outcome after spinal cord injury. As a crude prognostic biomarker, serum albumin concentration could be useful in cases where injury severity cannot be accurately assessed.

Conditioned pain modulation in elite athletes: a systematic review and meta-analysis

Background and aims Elite athletes reportedly have superior pain tolerances, but it is unclear if results extend to conditioned pain modulation (CPM). The aim of our study was to synthesize existing literature in order to determine whether CPM is increased in elite athletes compared to healthy controls. Methods A systematic review and random-effects meta-analysis was conducted. Cochrane Central Register of Controlled Trials, SPORTDiscus, PsycINFO, CINAHL, Web of Science, and PubMed were searched for English-language studies that examined CPM in adult elite athlete populations. Results Seven studies were identified; all were of poor to fair methodological quality. There was no overall difference in CPM between elite athletes and controls (Hedges g = 0.37, CI95 -0.03-0.76; p = 0.07). There was heterogeneity between studies, including one that reported significantly less CPM in elite athletes compared to controls. An exploratory meta-regression indicated that a greater number of hours trained per week was associated with higher CPM. Conclusions The overall number and quality of studies was low. Despite nominally favoring higher CPM in elite athletes, aggregate results indicate no significant difference compared to healthy controls. A possible factor explaining the high degree of variability between studies is the number of hours elite athletes spent training. Implications Based on available evidence, athletes do not have remarkable endogenous pain modulation compared to controls. High quality experimental studies are needed to address the effect of hours trained per week on CPM in athletes.

A pragmatic randomized controlled trial testing the effects of the international scientific SCI exercise guidelines on SCI chronic pain: protocol for the EPIC-SCI trial

STUDY DESIGN

Protocol for a pragmatic randomized controlled trial (the Exercise guideline Promotion and Implementation in Chronic SCI [EPIC-SCI] Trial).

PRIMARY OBJECTIVES

To test if home-/community-based exercise, prescribed according to the international SCI exercise guidelines, significantly reduces chronic bodily pain in adults with SCI.

SECONDARY OBJECTIVES

To investigate: (1) the effects of exercise on musculoskeletal and neuropathic chronic pain; (2) if reduced inflammation and increased descending inhibitory control are viable pathways by which exercise reduces pain; (3) the effects of chronic pain reductions on subjective well-being; and (4) efficiency of a home-/community-based exercise intervention.

SETTING

Exercise in home-/community-based settings; assessments in university-based laboratories in British Columbia, Canada.

METHOD

Eighty-four adults with chronic SCI, reporting chronic musculoskeletal or neuropathic pain, and not meeting the current SCI exercise guidelines, will be recruited and randomized to a 6-month Exercise or Wait-List Control condition. Exercise will occur in home/community settings and will be supported through behavioral counseling. All measures will be taken at baseline, 3-months and 6-months. Analyses will consist of linear mixed effect models, multiple regression analyses and a cost-utility analysis. The economic evaluation will examine the incremental costs and health benefits generated by the intervention compared with usual care.

ETHICS AND DISSEMINATION

The University of British Columbia Clinical Research Ethics Board approved the protocol (#H19-01650). Using an integrated knowledge translation approach, stakeholders will be engaged throughout the trial and will co-create and disseminate evidence-based recommendations and messages regarding the use of exercise to manage SCI chronic pain.

Beneficial "Pharmaceutical Pleiotropy" of Gabapentinoids in Spinal Cord Injury: A Case for Refining Standard-of-Care

Spinal cord injury results in devastating neurological deficits accompanied by lifelong disability and significant economic burden. While the development of novel compounds or cell-based interventions for spinal cord injury is unquestionably worthwhile, a complementary approach examines current standards of care and the degree to which these can be optimized to benefit long-term neurological function. Numerous classes of drugs, already in use in the acute phase of spinal cord injury, are intriguing because they (1) readily cross the blood-spinal cord barrier to modulate activity in the central nervous system and (2) are administered during a window of time in which neuroprotection, and even some repair, are feasible. Here, we review a rare case of convergent lines of evidence from both preclinical and human studies to support the early administration of a class of drug (ie, gabapentinoids) to both foster motor recovery and reduce the severity of neuropathic pain.

A Cervical Spinal Cord Hemi-Contusion Injury Model Based on Displacement Control in Non-Human Primates (Macaca fascicularis)

Non-human primate (NHP) spinal cord injury (SCI) models can be informative in the evaluation of treatments that show promise in rodent models prior to translation to humans. In the present study, we aimed to establish a cervical spinal hemi-contusion model with controlled displacement and evaluate the abnormalities in behavior, electrophysiology, histology, and magnetic resonance imaging. Twelve adult NHPs were divided into an SCI group (n = 8, 24 and 48 weeks) and a control group (n = 4). An impactor (Φ = 4 mm) was driven to compress the left C5 cord at 800 mm/sec. The contusion displacement and peak force was 4.08 ± 0.17 mm and 19.8 ± 4.6 N. The behavioral assessment showed a consistent dysfunction below the wrist and spontaneous recovery of limb function after injury. Lesion length and lesion area at the epicenter based on T2 hyperintensity were 5.68 ± 0.47 mm and 5.99 ± 0.24 mm² at 24 weeks post-injury (wpi), and 5.29 ± 0.17 mm and 5.95 ± 0.24 mm² at 48 wpi. The spared spinal cord area immuno-positive for glial fibrillary acidic protein was significantly reduced, while the staining intensity increased at 24 wpi and 48 wpi, compared with the sham group. Ipsilateral somatosensory and motor evoked potentials were dynamic, increasing in latency and decreasing in amplitude compared with pre-operative values or the contralateral values, and correlated to varying degrees with behavioral outcomes. A shift in size-frequency distribution of sensory neurons of the dorsal root ganglia (DRG) was consistent with a loss of large-diameter cells. The present study demonstrated that the NHP SCI model resulted in consistent unilateral limb dysfunction and potential plasticity in the face of loss of spinal cord and DRG tissue.

Biomarkers in Traumatic Spinal Cord Injury—Technical and Clinical Considerations: A Systematic Review

Objective. To examine (1) if serological or cerebrospinal fluid (CSF) biomarkers can be used as diagnostic and/or prognostic tools in patients with spinal cord injury (SCI) and (2) if literature provides recommendations regarding timing and source of biomarker evaluation. Data Sources. A systematic literature search to identify studies reporting on diagnostic and prognostic blood and/or CSF biomarkers in SCI was conducted in PubMed/MEDLINE, CINAHL, Science Direct, The Cochrane Library, ISI Web of Science, and PEDro. Study Selection. Clinical trials, cohort, and pilot studies on patients with traumatic SCI investigating at least one blood or CSF biomarker were included. Following systematic screening, 19 articles were included in the final analysis. PRISMA guidelines were followed to conduct this review. Data Extraction. Independent extraction of articles was completed by 2 authors using predefined inclusion criteria and study quality indicators. Data Synthesis. Nineteen studies published between 2002 and April 2019 with 1596 patients were included in the systematic review. In 14 studies, blood biomarkers were measured, 4 studies investigated CSF biomarkers, and 1 study used both blood and CSF samples. Conclusions. Serum/CSF concentrations of several biomarkers (S100b, IL-6, GFAP, NSE, tau, TNF-α, IL-8, MCP-1, pNF-H, and IP-10) following SCI are highly time dependent and related to injury severity. Future studies need to validate these markers as true biomarkers and should control for secondary complications associated with SCI. A deeper understanding of secondary pathophysiological events after SCI and their effect on biomarker dynamics may improve their clinical significance as surrogate parameters in future clinical studies.

Contact Heat Evoked Potentials Are Responsive to Peripheral Sensitization: Requisite Stimulation Parameters

The sensitizing effect of capsaicin has been previously characterized using laser and contact heat evoked potentials (LEPs and CHEPs) by stimulating in the primary area of hyperalgesia. Interestingly, only CHEPs reveal changes consistent with notion of peripheral sensitization (i.e., reduced latencies). The aim of this study was to investigate contact heat stimulation parameters necessary to detect peripheral sensitization related to the topical application of capsaicin, and therefore significantly improve the current method of measuring peripheral sensitization via CHEPs. Rapid contact heat stimulation (70°C/s) was applied from three different baseline temperatures (35, 38.5, and 42°C) to a 52°C peak temperature, before and after the topical application of capsaicin on the hand dorsum. Increased pain ratings in the primary area of hyperalgesia were accompanied by reduced N2 latency. Changes in N2 latency were, however, only significant following stimulation from 35 and 38.5°C baseline temperatures. These findings suggest that earlier recruitment of capsaicin-sensitized afferents occurs between 35 and 42°C, as stimulations from 42°C baseline were unchanged by capsaicin. This is in line with reduced thresholds of type II A-delta mechanoheat (AMH) nociceptors following sensitization. Conventional CHEP stimulation, with a baseline temperature below 42°C, is well suited to objectively detect evidence of peripheral sensitization.

Using ecological momentary assessment to evaluate neuropathic pain experienced by adults with SCI: recommendations and participant perceptions

PURPOSE

Neuropathic pain is a debilitating consequence of spinal cord injury. Ecological momentary assessment can be a valuable research tool for understanding temporal fluctuations in neuropathic pain and designing effective management strategies. The objectives of this study were to (a) describe strategies necessary to adapt ecological momentary assessment to measure neuropathic pain in adults with spinal cord injury, and (b) explore participant perceptions of using ecological momentary assessment to measure pain sensations.

METHODS

End-users with spinal cord injury provided input to guide development of an ecological momentary assessment protocol. Six adults with spinal cord injury (ages 27-50 years, M = 39.33 ± 8.24) engaged in the six-day protocol and completed six daily neuropathic pain assessments. Upon finishing participants completed a semi-structured interview regarding their protocol experiences. A qualitative content analysis was used to analyze the interview data.

RESULTS

Participants reported that this specific ecological momentary assessment protocol was unobtrusive to their daily routines, and effectively captured their neuropathic pain sensations. However, participants experienced increased neuropathic pain due to the repeated nature of assessments.

CONCLUSION

Ecological momentary assessment can capture the dynamic nature of neuropathic pain experienced by persons with spinal cord injury. However, caution should be taken when designing intensive pain-related protocols to minimize pain exacerbation.IMPLICATIONS FOR REHABILITATIONNeuropathic pain affects up to 75% of people with spinal cord injury and is one of the most frequently occurring, debilitating forms of pain.Appropriate and feasible pain data collection methods are necessary to acquire a better understanding of how neuropathic pain manifests in people with spinal cord injury.Implementing ecological momentary assessment in a rehabilitation setting may help facilitate the monitoring of neuropathic pain for both rehabilitation professionals and persons with SCI.Using ecological momentary assessment may lead to a better understanding of individual temporal patterns of neuropathic pain that could inform the design of tailored neuropathic pain management techniques.

Myelin Water Fraction and Intra/Extracellular Water Geometric Mean T2 Normative Atlases for the Cervical Spinal Cord from 3T MRI

BACKGROUND AND PURPOSE

Acquiring and interpreting quantitative myelin-specific MRI data at an individual level is challenging because of technical difficulties and natural myelin variation in the population. To overcome these challenges, we used multiecho T₂ myelin water imaging (MWI) to create T₂ metric healthy population atlases that depict the mean and variation of myelin water fraction (MWF), and intra- and extracellular water mobility as described by geometric mean T₂ (IEGMT₂ ).

METHODS

Cervical cord MWI was performed at 3T on 20 healthy individuals (10M/10F, mean age: 36 years) and 3 relapsing remitting multiple sclerosis (RRMS) participants (1M/2F, age: 39/42/37 years). Anatomical data were collected for the purpose of image segmentation and registration. Atlases were created by coregistering and averaging T₂ metrics from all controls. Voxel-wise z-score maps from 3 RRMS participants were produced to demonstrate the preliminary utility of the MWF and IEGMT₂ atlases.

RESULTS

The average MWF atlas provides a representation of myelin in the spinal cord consistent with well-known spinal cord anatomical characteristics. The IEGMT₂ atlas also depicted structural variations in the spinal cord. Z-score analysis illustrated distinct abnormalities in MWF and IEGMT₂ in the 3 RRMS cases.

CONCLUSIONS

Our findings highlight the potential for using a quantitative T₂ relaxation metric atlas to visualize and detect pathology in spinal cord. Our MWF and IEGMT₂ atlases (URL: https://sourceforge.net/projects/mwi-spinal-cord-atlases/) can serve as normative references in the cervical spinal cord for other studies.

Myelin Water Atlas: A Template for Myelin Distribution in the Brain

BACKGROUND AND PURPOSE

Myelin water imaging (MWI) is a magnetic resonance imaging technique that quantifies myelin in-vivo. Although MWI has been extensively applied to study myelin-related diseases in groups, clinical use in individual patients is challenging mainly due to population heterogeneity. The purpose of this study was twofold: (1) create a normative brain myelin water atlas depicting the population mean and regional variability of myelin content; and (2) apply the myelin atlas to assess the degree of demyelination in individuals with multiple sclerosis (MS).

METHODS

3T MWI was performed on 50 healthy adults (25 M/25 F, mean age 25 years [range 17-42 years]). The myelin water atlas was created by averaging coregistered myelin water fraction (MWF) maps from all healthy individuals. To illustrate the preliminary utility of the atlas, white matter (WM) regional MWF variations were evaluated and voxel-wise z-score maps (z < -1.96) from the MWI of three MS participants were produced to assess individually the degree of demyelination.

RESULTS

The myelin water atlas demonstrated significant MWF variation across control WM. No significant MWF differences were found between male and female healthy participants. MS z-score maps revealed diffuse regions of demyelination in the two participants with Expanded Disability Status Scale (EDSS) = 2.0 but not in the participant with EDSS = 0.

CONCLUSIONS

The myelin water atlas can be used as a reference (URL: https://sourceforge.net/projects/myelin-water-atlas/) to demonstrate areas of demyelination in individual MS participants. Future studies will expand the atlas age range, account for education, and other variables that may affect myelination.

A Longitudinal Study of the Neurologic Safety of Acute Baclofen Use After Spinal Cord Injury

The objective of our study was to determine whether treatment with baclofen is neurologically safe with respect to exposure during recovery from spinal cord injury. We performed a secondary longitudinal analysis of a cohort of adult patients with traumatic acute spinal cord injury. Cumulative baclofen dose was computed over the first 4 weeks following injury from concomitant medication information from a completed clinical trial. The main outcome measure was neurologic status, which was assessed over 52 weeks with "marked recovery" defined as the conversion to higher sensory and motor function. To complete the drug safety profile, drug toxicity was assessed with assays from standard blood work. Multivariable Cox regression was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs). Of the cohort (n = 651), 18% (n = 115) received baclofen within 4 weeks post injury. Baclofen use was associated with higher rates of marked neurologic recovery, even after adjustment for injury severity (HR = 2.1, 95% CI 1.5-3.0 for high dose vs none). Baclofen exposure was not associated with liver or renal side effects. The use of other medications indicated for spasticity was not associated with neurological outcomes. Overall, this longitudinal analysis provides level 3 evidence on the neurologic safety of baclofen and potential beneficial effects on recovery in the early days after acute traumatic spinal cord injury. The usefulness of concomitant medication files from completed clinical trials is highlighted. We also highlight the importance of incorporating logical patient questions and neurological outcomes into research addressing drug safety.

Rapid myelin water imaging for the assessment of cervical spinal cord myelin damage

Background

Rapid myelin water imaging (MWI) using a combined gradient and spin echo (GRASE) sequence can produce myelin specific metrics for the human brain. Spinal cord MWI could be similarly useful, but technical challenges have hindered routine application. GRASE rapid MWI was recently successfully implemented for imaging of healthy cervical spinal cord and may complement other advanced imaging methods, such as diffusion tensor imaging (DTI) and quantitative T₁ (qT₁).

Objective

To demonstrate the feasibility of cervical cord GRASE rapid MWI in multiple sclerosis (MS), primary lateral sclerosis (PLS) and neuromyelitis optica spectrum disorder (NMO), with comparison to DTI and qT₁ metrics.

Methods

GRASE MWI, DTI and qT₁ data were acquired in 2 PLS, 1 relapsing-remitting MS (RRMS), 1 primary-progressive MS (PPMS) and 2 NMO subjects, as well as 6 age (±3 yrs) and sex matched healthy controls (HC). Internal cord structure guided template registrations, used for region of interest (ROI) analysis. Z score maps were calculated for the difference between disease subject and mean HC metric values.

Results

PLS subjects had low myelin water fraction (MWF) in the lateral funiculi compared to HC. RRMS subject MWF was heterogeneous within the cord. The PPMS subject showed no trends in ROI results but had a region of low MWF Z score corresponding to a focal lesion. The NMO subject with a longitudinally extensive transverse myelitis lesion had low values for whole cord mean MWF of 12.8% compared to 24.3% (standard deviation 2.2%) for HC. The NMO subject without lesions also had low MWF compared to HC. DTI and qT₁ metrics showed similar trends, corroborating the MWF results and providing complementary information.

Conclusion

GRASE is sufficiently sensitive to detect decreased myelin within MS spinal cord plaques, NMO lesions, and PLS diffuse spinal cord injury. Decreased MWF in PLS is consistent with demyelination secondary to motor neuron degeneration. GRASE MWI is a feasible method for rapid assessment of myelin content in the cervical spinal cord and provides complementary information to that of DTI and qT₁ measures.

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Downstream myelin changes in motor tracts of primary lateral sclerosis spinal cord.

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Low myelin water fraction in multiple sclerosis and neuromyelitis optica cord lesions.

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Diffuse demyelination evidence in neuromyelitis optica normal-appearing white matter.

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Myelin water imaging provides complementary information to diffusion and T₁ metrics.

New life for an old idea: Assessing tonic heat pain by means of participant controlled temperature

BACKGROUND

Temporal changes of pain perception to prolonged tonic heat pain are conventionally assessed using a computerized visual analog scale. Such a rating-based approach is, however, prone to floor and ceiling effects, which limit the assessment of temporal changes in perception. Thus, alternative methods that overcome these shortcomings are warranted.

NEW METHOD

The aim of this study was to assess the feasibility and reliability of a psychophysical approach, i.e., participant-controlled temperature (PCT), to evaluate ongoing human perception of tonic heat pain. Fifty participants were presented with a 45 °C stimulus on the non-dominant hand, and were instructed to maintain their initial sensation for two minutes via a feedback controller in the dominant hand. A subset of participants (n = 17) performed PCT tonic heat protocols on two different days to determine the test-retest reliability. As participants controlled temperature to maintain a stable pain perception, any adjustments made reflected shifts in their perception of heat.

RESULTS

In 33 (71.7%) participants, we observed an initial adaptation (participant increased temperature) followed by temporal summation of pain (participant decreased temperature). Twelve participants (26.1%) showed only adaptation and one (2.2%) only temporal summation. No sex differences were observed, nor did the initial rating of pain have an effect on PCT outcomes. Temporal summation of pain showed moderate to substantial reliability upon retest.

CONCLUSIONS

PCT represents can be reliably performed using a contact heat stimulator to measure the temporal summation of pain. The standardized setup and overall good reliability of the outcome measures facilitate a sound implementation into the clinical work-up of patients with pain conditions.

Ecological fallacy as a novel risk factor for poor translation in neuroscience research: A systematic review and simulation study

BACKGROUND

Translational neuroscience is largely concerned with establishing causal links between biological processes and functional outcomes. Exciting new methods have emerged and top-tier biomedical journals are placing increasingly high demand for experiments that link outcomes. One pitfall to making these connections is the "ecological fallacy"-establishing a relationship between outcomes based on aggregate (averaged) results (a distinct issue from correlation vs causation).

METHODS

To showcase the ecological fallacy, we first used simulated data to define and demonstrate the problem. Next, we performed a systematic review to determine the prevalence of the fallacy in top-tier biomedical journals (Science, Nature Medicine, Neuron, Nature, Nature Neuroscience, Cell). Based on our own research interests and specializations, we specifically focused on recent publications in the area of spinal cord injury and regenerative medicine.

RESULTS

Of the articles reviewed which examined a relationship between central nervous system regeneration and a behavioural outcome, 100% (21/21) were subject to possible ecological fallacy.

CONCLUSIONS

Ecological fallacy is highly prevalent in neuroscience research and could partially account for translation failures in this field. Reporting guidelines for in vivo experiments should include subject-level correlation analyses for the primary outcomes.

Not Hot, but Sharp: Dissociation of Pinprick and Heat Perception in Snake Eye Appearance Myelopathy

Following a traumatic spinal cord injury, a 53-year-old male developed a central cord syndrome with at-level neuropathic pain. Magnetic resonance imaging revealed a classical “snake eye” appearance myelopathy, with marked hyperintensities at C5-C7. Clinical examination revealed intact pinprick sensation coupled with lost or diminished thermal/heat sensation. This dissociation could be objectively confirmed through multi-modal neurophysiological assessments. Specifically, contact heat evoked potentials were lost at-level, while pinprick evoked potentials were preserved. This pattern corresponds with that seen after surgical commissural myelotomy. To our knowledge, this is the first time such a dissociation has been objectively documented, highlighting the diagnostic potential of multi-modal neurophysiological assessments. In future studies, a comprehensive assessment of different nociceptive modalities may help elucidate the pathophysiology of neuropathic pain.

Progression of Neuropathic Pain after Acute Spinal Cord Injury: A Meta-Analysis and Framework for Clinical Trials

The translation of therapeutic interventions to humans with spinal cord injury with the goal of promoting growth and repair in the central nervous system could, inadvertently, drive mechanisms associated with the development of neuropathic pain. A framework is needed to evaluate the probability that a therapeutic intervention for acute spinal cord injury modifies the progression of neuropathic pain. We analyzed a large, longitudinal dataset from the European Multi-Center Study about Spinal Cord Injury (EMSCI) and compared these observations with a previously published Swedish/Danish cohort. A meta-analysis was performed to produce aggregate estimates for the transition period between 1-6 months and the transition period between 1-12 months after injury. A secondary analysis used logistic regression to explore associations between the progression of neuropathic pain and demographics, pain characteristics, and injury characteristics. For overall neuropathic pain, 72% presenting with pain symptoms at one month reported persisting symptoms at six months, and 23% who did not have neuropathic pain at one month later had it develop. From 1-12 months, there was a similar likelihood of pain persisting (69%) and slightly higher rate of pain developing (36%). Characteristics that were significantly associated with the progression of pain included age and sensory and motor preservation. We provide historical benchmarks for estimating the progression of neuropathic pain during the first year after acute SCI. This information will be useful for comparison and evaluating safety during early phase acute spinal cord injury trials.

Sensorimotor plasticity after spinal cord injury: a longitudinal and translational study

Objective

The objective was to track and compare the progression of neuroplastic changes in a large animal model and humans with spinal cord injury.

Methods

A total of 37 individuals with acute traumatic spinal cord injury were followed over time (1, 3, 6, and 12 months post-injury) with repeated neurophysiological assessments. Somatosensory and motor evoked potentials were recorded in the upper extremities above the level of injury. In a reverse-translational approach, similar neurophysiological techniques were examined in a porcine model of thoracic spinal cord injury. Twelve Yucatan mini-pigs underwent a contusive spinal cord injury at T10 and tracked with somatosensory and motor evoked potentials assessments in the fore- and hind limbs pre- (baseline, post-laminectomy) and post-injury (10 min, 3 h, 12 weeks).

Results

In both humans and pigs, the sensory responses in the cranial coordinates of upper extremities/forelimbs progressively increased from immediately post-injury to later time points. Motor responses in the forelimbs increased immediately after experimental injury in pigs, remaining elevated at 12 weeks. In humans, motor evoked potentials were significantly higher at 1-month (and remained so at 1 year) compared to normative values.

Conclusions

Despite notable differences between experimental models and the human condition, the brain's response to spinal cord injury is remarkably similar between humans and pigs. Our findings further underscore the utility of this large animal model in translational spinal cord injury research.

Contact heat evoked potentials: Reliable acquisition from lower extremities

OBJECTIVE

To investigate test-retest reliability of contact heat evoked potentials (CHEPs) from lower extremities using two different stimulation protocols, i.e., normal and increased baseline temperature.

METHODS

A total of 32 able-bodied subjects were included and a subset (N = 22) was retested. CHEPs were recorded from three different dermatomes of the lower extremity (i.e., L2, L5, and S2). Test-retest reliability of CHEPs acquisition after simulation in various lower limb dermatomes using different stimulation protocols was analyzed.

RESULTS

The study revealed an improved acquisition of CHEPS employing the increased baseline protocol, particularly when stimulating more distal sites, i.e., dermatome L5 and S2. Based on repeatability coefficients, CHEP latency (N2 potential) emerged as the most robust CHEP parameter. Although CHEP amplitudes (N2P2 complex) and pain ratings were decreased in the retest, amplitudes still showed fair to excellent intraclass correlation coefficients using normal baseline or increased baseline temperature, respectively.

CONCLUSIONS

This is the first study to demonstrate that CHEPs acquisition from the lower extremities is improved by increasing the baseline temperature of the thermode.

SIGNIFICANCE

This study highlights the usability of CHEPs as a viable diagnostic method to study small fiber integrity.

Serum Albumin Predicts Long-Term Neurological Outcomes After Acute Spinal Cord Injury

Background. There is a need to identify reliable biomarkers of spinal cord injury recovery for clinical practice and clinical trials. Objective. Our objective was to correlate serum albumin levels with spinal cord injury neurological outcomes. Methods. We performed a secondary analysis of patients with traumatic spinal cord injury (n = 591) participating in the Sygen clinical trial. Serum albumin concentrations were obtained as part of routine blood chemistry analysis, at trial entry (24-72 hours), 1, 2, and 4 weeks after injury. The primary outcomes were “marked recovery” and lower extremity motor scores, derived from the International Standards for the Neurological Classification of Spinal Cord Injury. Data were analyzed with multivariable logistic and linear regression to adjust for potential confounders. Results. Serum albumin was significantly associated with spinal cord injury neurological outcomes. Higher serum albumin concentrations at 1, 2, and 4 weeks were associated with higher 52-week lower extremity motor score. Similarly, the odds of achieving “marked neurological recovery” was greater for individuals with higher serum albumin concentrations. The association between serum albumin concentrations and neurological outcomes was independent of initial injury severity, treatment with GM-1, and polytrauma. Conclusions. In spinal cord injury, serum albumin is an independent marker of long-term neurological outcomes. Serum albumin could serve as a feasible biomarker for prognosis at the time of injury and stratification in clinical trials.

Assessing structure and function of myelin in cervical spondylotic myelopathy: Evidence of demyelination

PURPOSE

To assess the extent of demyelination in cervical spondylotic myelopathy (CSM) using myelin water imaging (MWI) and electrophysiologic techniques.

METHODS

Somatosensory evoked potentials (SSEPs) and MWI were acquired in 14 patients with CSM and 18 age-matched healthy controls. MWI was performed on a 3.0T whole body magnetic resonance scanner. Myelin water fraction (MWF) was extracted for the dorsal columns and whole cord. SSEPs and MWF were also compared with conventional MRI outcomes, including T2 signal intensity, compression ratio, maximum spinal cord compression (MSCC), and maximum canal compromise (MCC).

RESULTS

Group analysis showed marked differences in T2 signal intensity, compression ratio, MSCC, and MCC between healthy controls and patients with CSM. There were no group differences in MWF and SSEP latencies. However, patients with CSM with pathologic SSEPs exhibited reduction in MWF (p < 0.05). MWF was also correlated with SSEP latencies.

CONCLUSION

Our findings provide evidence of decreased myelin content in the spinal cord associated with impaired spinal cord conduction in patients with CSM. While conventional MRI are of great value to define the extent of cord compression, they show a limited correlation with functional deficits (i.e., delayed SSEPs). MWI provides independent and complementary readouts to spinal cord compression, with a high specificity to detect impaired conduction.

Open Access Platforms in Spinal Cord Injury: Existing Clinical Trial Data to Predict and Improve Outcomes

Recovery from acute spinal cord injury (SCI) is characterized by extensive heterogeneity, resulting in uncertain prognosis. Reliable prediction of recovery in the acute phase benefits patients and their families directly, as well as improves the likelihood of detecting efficacy in clinical trials. This issue of heterogeneity is not unique to SCI. In fields such as traumatic brain injury, Parkinson's disease, and amyotrophic lateral sclerosis, one approach to understand variability in recovery has been to make clinical trial data widely available to the greater research community. We contend that the SCI community should adopt a similar approach in providing open access clinical trial data.

Thermal grill conditioning: Effect on contact heat evoked potentials

The ‘thermal grill illusion’ (TGI) is a unique cutaneous sensation of unpleasantness, induced through the application of interlacing warm and cool stimuli. While previous studies have investigated optimal parameters and subject characteristics to evoke the illusion, our aim was to examine the modulating effect as a conditioning stimulus. A total of 28 healthy control individuals underwent three testing sessions on separate days. Briefly, 15 contact heat stimuli were delivered to the right hand dorsum, while the left palmar side of the hand was being conditioned with either neutral (32 °C), cool (20 °C), warm (40 °C), or TGI (20/40 °C). Rating of perception (numeric rating scale: 0–10) and evoked potentials (i.e., N1 and N2P2 potentials) to noxious contact heat stimuli were assessed. While cool and warm conditioning decreased cortical responses to noxious heat, TGI conditioning increased evoked potential amplitude (N1 and N2P2). In line with other modalities of unpleasant conditioning (e.g., sound, visual, and olfactory stimulation), cortical and possibly sub-cortical modulation may underlie the facilitation of contact heat evoked potentials.

Normative data for the segmental acquisition of contact heat evoked potentials in cervical dermatomes

Contact heat evoked potentials (CHEPs) represent a neurophysiological approach to assess conduction in the spinothalamic tract. The aim of this study was to establish normative values of CHEPs acquired from cervical dermatomes (C4, C6, C8) and examine the potential confounds of age, sex, and height. 101 (49 male) healthy subjects of three different age groups (18–40, 41–60, and 61–80 years) were recruited. Normal (NB, 35–52 °C) followed by increased (IB, 42–52 °C) baseline stimulation protocols were employed to record CHEPs. Multi-variate linear models were used to investigate the effect of age, sex, and height on the CHEPs parameters (i.e., N2 latency, N2P2 amplitude, rating of perceived intensity). Compared to NB, IB stimulation reduced latency jitter within subjects, yielding larger N2P2 amplitudes, and decreased inter-subject N2 latency variability. Age was associated with reduced N2P2 amplitude and prolonged N2 latency. After controlling for height, male subjects had significantly longer N2 latencies than females during IB stimulation. The study provides normative CHEPs data in a large cohort of healthy subjects from segmentally examined cervical dermatomes. Age and sex were identified as important factors contributing to N2 latency and N2P2 amplitude. The normative data will improve the diagnosis of spinal cord pathologies.

Neuropathic pain following traumatic spinal cord injury: Models, measurement, and mechanisms

Neuropathic pain following spinal cord injury (SCI) is notoriously difficult to treat and is a high priority for many in the SCI population. Resolving this issue requires animal models fidelic to the clinical situation in terms of injury mechanism and pain phenotype. This Review discusses the means by which neuropathic pain has been induced and measured in experimental SCI and compares these with human outcomes, showing that there is a substantial disconnection between experimental investigations and clinical findings in a number of features. Clinical injury level is predominantly cervical, whereas injury in the laboratory is modeled mainly at the thoracic cord. Neuropathic pain is primarily spontaneous or tonic in people with SCI (with a relatively smaller incidence of allodynia), but measures of evoked responses (to thermal and mechanical stimuli) are almost exclusively used in animals. There is even the question of whether pain per se has been under investigation in most experimental SCI studies rather than simply enhanced reflex activity with no affective component. This Review also summarizes some of the problems related to clinical assessment of neuropathic pain and how advanced imaging techniques may circumvent a lack of patient/clinician objectivity and discusses possible etiologies of neuropathic pain following SCI based on evidence from both clinical studies and animal models, with examples of cellular and molecular changes drawn from the entire neuraxis from primary afferent terminals to cortical sensory and affective centers. © 2016 Wiley Periodicals, Inc.