Perceptual threshold to cutaneous electrical stimulation in patients with spinal cord injury

Quantitative electrophysiological assessments as predictive markers of lower limb motor recovery after spinal cord injury: a pilot study with an adaptive trial design

Study design

Observational, cohort study.

Objectives

(1) Determine the feasibility and relevance of assessing corticospinal, sensory, and spinal pathways early after traumatic spinal cord injury (SCI) in a rehabilitation setting. (2) Validate whether electrophysiological and magnetic resonance imaging (MRI) measures taken early after SCI could identify preserved neural pathways, which could then guide therapy.

Setting

Intensive functional rehabilitation hospital (IFR).

Methods

Five individuals with traumatic SCI and eight controls were recruited. The lower extremity motor score (LEMS), electrical perceptual threshold (EPT) at the S2 dermatome, soleus (SOL) H-reflex, and motor evoked potentials (MEPs) in the tibialis anterior (TA) muscle were assessed during the stay in IFR and in the chronic stage (>6 months post-SCI). Control participants were only assessed once. Feasibility criteria included the absence of adverse events, adequate experimental session duration, and complete dataset gathering. The relationship between electrophysiological data collected in IFR and LEMS in the chronic phase was studied. The admission MRI was used to calculate the maximal spinal cord compression (MSCC).

Results

No adverse events occurred, but a complete dataset could not be collected for all subjects due to set-up configuration limitations and time constraints. EPT measured at IFR correlated with LEMS in the chronic phases (r = −0.67), whereas SOL H/M ratio, H latency, MEPs and MSCC did not.

Conclusions

Adjustments are necessary to implement electrophysiological assessments in an IFR setting. Combining MRI and electrophysiological measures may lead to better assessment of neuronal deficits early after SCI.

Are Reports of Pain, Disability, Quality of Life, Psychological Factors, and Central Sensitization Related to Outcomes of Quantitative Sensory Testing in Patients Suffering From Chronic Whiplash Associated Disorders?

BACKGROUND

Chronic whiplash associated disorders (CWAD) are characterized by long-lasting symptoms of neck pain occurring after an acceleration-deceleration injury. Central sensitization (CS) has been suggested as the possible underlying mechanism for these symptoms, and is characterized by changes in the central nervous system. Besides CS, psychological factors are believed to play an important role in the experience of (chronic) pain.

OBJECTIVE

Investigating the relationships between self-reported pain, disability, quality of life, psychological factors, and symptoms of CS; and electrical-based quantitative sensory testing (QST) outcomes in CWAD patients. Secondly, to investigate the differences in QST between CWAD patients and pain-free controls.

METHODS

Seventy-two individuals with CWAD and 55 pain-free controls underwent electrical stimuli-based QST. Detection and pain thresholds (EPT), temporal summation (TS), and conditioned pain modulation were examined. Spearman correlation and linear mixed models analyses were performed to assess, respectively, the hypothesized associations and group differences in QST.

RESULTS

The Pain Catastrophizing magnification subscale correlated with the left wrist EPT (r=-0.332; P=0.004), and the Pain Anxiety Symptom Scale-20 with the left wrist (r=-0.325; P=0.005) and ankle (r=-0.330; P=0.005) EPT. TS at the ankle correlated with the CS inventory (r=0.303; P=0.010), Short Form 36 pain subscale (r=-0.325; P=0.005), and Illness Perception Questionnaire revised consequences subscale (r=0.325; P=0.005). EPTs left (P=0.011) and right wrist (P=0.023) were lower in the CWAD group, but conditioned pain modulation and TS did not differ between groups.

CONCLUSION

QST outcomes relate to psychological constructs, rather than to self-reported pain intensity and distribution. Local hyperalgesia was found in individuals with CWAD, but no differences in endogenous pain facilitation nor inhibition.

A contemporary neuroscience approach compared to biomedically focused education combined with symptom-contingent exercise therapy in people with chronic whiplash associated disorders: a randomized controlled trial protocol

BACKGROUND

To address the need for a better treatment of chronic whiplash associated disorders (WAD), a contemporary neuroscience approach can be proposed.

OBJECTIVE

To examine the effectiveness of a contemporary neuroscience approach, comprising pain neuroscience education, stress management, and cognition-targeted exercise therapy versus conventional physical therapy for reducing disability (primary outcome measure) and improving quality of life and reducing pain, central sensitization, and psychological problems (secondary outcome measures) in people with chronic WAD.

METHODS

The study is a multi-center, two-arm randomized, controlled trial with 1-year follow-up and will be performed in two university-based and one regional hospital. People with chronic WAD (n=120) will be recruited. The experimental group will receive pain neuroscience education followed by cognition-targeted exercise therapy, and stress management. The control group will receive biomedically focused education followed by graded and active exercise therapy focusing on muscle endurance, strength, and flexibility, and ergonomic principles. The treatment will have a duration of 16 weeks. Functional status (Neck Disability Index) is the primary outcome measure. Secondary outcome measures include quality of life, pain, central sensitization, and psychological and socio-economic factors. In addition, electroencephalography will measure brain activity at rest and during a conditioned pain modulation paradigm. Assessments will take place at baseline, immediately post-treatment and at 6 and 12 months follow-up.

CONCLUSIONS

This study will examine whether a contemporary neuroscience approach is superior over conventional physical therapy for improving functioning, quality of life, and reducing pain, central sensitization, and psychological problems in people with chronic WAD.

Applicability and tolerability of electrical stimulation applied to the upper and lower leg skin surface for cueing applications in Parkinson's disease

Due to possible sensory impairments in people with Parkinson's disease, several methodological aspects of electrical stimulation as a potential cueing method remain to be explored. This study aimed to investigate the applicability and tolerability of sensory and motor electrical stimulation in 10 people with Parkinson's disease. The study focused on assessing the electrical stimulation voltages and visual analogue scale discomfort scores at the electrical sensory, motor, discomfort, and pain thresholds. Results show that sensory electrical stimulation at the tibialis anterior, soleus, hamstrings, and quadriceps stimulation sites was applicable and tolerable for 6/10, 10/10, 9/10, and 10/10 participants, respectively. Furthermore, motor electrical stimulation at the tibialis anterior, soleus, hamstrings, and quadriceps stimulation sites were applicable and tolerable for 7/10, 7/10, 7/10, and 8/10 participants, respectively. Interestingly, the thresholds for the lower leg were higher than those of the upper leg. The data presented in this paper indicate that sensory and motor electrical stimulation is applicable and tolerable for cueing applications in people with Parkinson's disease. Sensory electrical stimulation was applicable and tolerable at the soleus and quadriceps sites. Motor electrical stimulation was not tolerable for two participants at any of the proposed stimulation sites. Therefore, future studies investigating motor electrical stimulation cueing, should apply it with caution in people with Parkinson's disease.

Retraining walking over ground in a powered exoskeleton after spinal cord injury: a prospective cohort study to examine functional gains and neuroplasticity

Background

Powered exoskeletons provide a way to stand and walk for people with severe spinal cord injury. Here, we used the ReWalk exoskeleton to determine the training dosage required for walking proficiency, the sensory and motor changes in the nervous system with training, and the functionality of the device in a home-like environment.

Methods

Participants with chronic (> 1 yr) motor complete or incomplete spinal cord injury, who were primarily wheelchair users, were trained to walk in the ReWalk for 12 weeks. Measures were taken before, during, immediately after, and 2–3 months after training. Measures included walking progression, sitting balance, skin sensation, spasticity, and strength of the corticospinal tracts.

Results

Twelve participants were enrolled with 10 completing training. Training progression and walking ability: The progression in training indicated about 45 sessions to reach 80% of final performance in training. By the end of training, participants walked at speeds of 0.28–0.60 m/s, and distances of 0.74–1.97 km in 1 h. The effort of walking was about 3.3 times that for manual wheelchair propulsion. One non-walker with an incomplete injury became a walker without the ReWalk after training. Sensory and motor measures: Sitting balance was improved in some, as seen from the limits of stability and sway speed. Neuropathic pain showed no long term changes. Change in spasticity was mixed with suggestion of differences between those with high versus low spasticity prior to training. The strength of motor pathways from the brain to back extensor muscles remained unchanged. Adverse events: Minor adverse events were encountered by the participants and trainer (skin abrasions, non-injurious falls). Field testing: The majority of participants could walk on uneven surfaces outdoors. Some limitations were encountered in home-like environments.

Conclusion

For individuals with severe SCI, walking proficiency in the ReWalk requires about 45 sessions of training. The training was accompanied by functional improvements in some, especially in people with incomplete injuries.

Trial registration

NCT02322125 Registered 22 December 2014.

Electronic supplementary material

The online version of this article (10.1186/s12984-019-0585-x) contains supplementary material, which is available to authorized users.

Application of electrophysiological measures in spinal cord injury clinical trials: a narrative review

STUDY DESIGN

Narrative review.

OBJECTIVES

To discuss how electrophysiology may contribute to future clinical trials in spinal cord injury (SCI) in terms of: (1) improvement of SCI diagnosis, patient stratification and determination of exclusion criteria; (2) the assessment of adverse events; and (3) detection of therapeutic effects following an intervention.

METHODS

An international expert panel for electrophysiological measures in SCI searched and discussed the literature focused on the topic.

RESULTS

Electrophysiology represents a valid method to detect, track, and quantify readouts of nerve functions including signal conduction, e.g., evoked potentials testing long spinal tracts, and neural processing, e.g., reflex testing. Furthermore, electrophysiological measures can predict functional outcomes and thereby guide rehabilitation programs and therapeutic interventions for clinical studies.

CONCLUSION

Objective and quantitative measures of sensory, motor, and autonomic function based on electrophysiological techniques are promising tools to inform and improve future SCI trials. Complementing clinical outcome measures, electrophysiological recordings can improve the SCI diagnosis and patient stratification, as well as the detection of both beneficial and adverse events. Specifically composed electrophysiological measures can be used to characterize the topography and completeness of SCI and reveal neuronal integrity below the lesion, a prerequisite for the success of any interventional trial. Further validation of electrophysiological tools with regard to their validity, reliability, and sensitivity are needed in order to become routinely applied in clinical SCI trials.

Challenging questions regarding the international standards

Objective/Context To highlight questions with regards to the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) and provide historical perspectives to help SCI professionals gain fuller insights into the classification system. Methods Frequently asked questions to the ISNCSCI were collected and a review of literature and personal communications with International Standards committee members and Chairs were undertaken. Results Background and explanations for nine questions, detailing decision processes and challenging classification rules are presented. Conclusion While the ISNCSCI can be challenging, this background and historical explanation may provide a greater understanding and the ability to critically analyze this classification system.

Afferent input and sensory function after human spinal cord injury

Spinal cord injury (SCI) often disrupts the integrity of afferent (sensory) axons projecting through the spinal cord dorsal columns to the brain. Examinations of ascending sensory tracts, therefore, are critical for monitoring the extent of SCI and recovery processes. In this review, we discuss the most common electrophysiological techniques used to assess transmission of afferent inputs to the primary motor cortex (i.e., afferent input-induced facilitation and inhibition) and the somatosensory cortex [i.e., somatosensory evoked potentials (SSEPs), dermatomal SSEPs, and electrical perceptual thresholds] following human SCI. We discuss how afferent input modulates corticospinal excitability by involving cortical and spinal mechanisms depending on the timing of the effects, which need to be considered separately for upper and lower limb muscles. We argue that the time of arrival of afferent input onto the sensory and motor cortex is critical to consider in plasticity-induced protocols in humans with SCI. We also discuss how current sensory exams have been used to detect differences between control and SCI participants but might be less optimal to characterize the level and severity of injury. There is a need to conduct some of these electrophysiological examinations during functionally relevant behaviors to understand the contribution of impaired afferent inputs to the control, or lack of control, of movement. Thus the effects of transmission of afferent inputs to the brain need to be considered on multiple functions following human SCI.

Time-Dependent Discrepancies between Assessments of Sensory Function after Incomplete Cervical Spinal Cord Injury

We recently demonstrated that the electrical perceptual threshold (EPT) examination reveals spared sensory function at lower spinal segments compared with the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) examination in humans with chronic incomplete cervical spinal cord injury (SCI). Here, we investigated whether discrepancies in sensory function detected by both sensory examinations change over time after SCI. Forty-five participants with acute (<1 year), chronic (≥1-10 years), and extended-chronic (>10 years) incomplete cervical SCI and 30 control subjects were tested on dermatomes C2-T4 bilaterally. EPT values were higher in subjects with acute (2.5 ± 0.8 mA), chronic (2.2 ± 0.7 mA), or extended-chronic (2.8 ± 1.1 mA) SCI compared with controls (1.0 ± 0.1 mA). The EPT examination detected sensory impairments in spinal segments above (2.3 ± 0.9) and below (4.2 ± 2.6) the level detected by the ISNCSCI sensory examination in participants with acute and chronic SCI, respectively. Notably, both examinations detected similar levels of spared sensory function in the extended-chronic phase of SCI (0.8 ± 0.5). A negative correlation was found between differences in EPT and ISNCSCI sensory levels and time post-injury. These observations indicate that discrepancies between EPT and ISNCSCI sensory scores are time-dependent, with the EPT revealing impaired sensory function above, below, or at the same spinal segment as the ISNCSCI examination. We propose that the EPT is a sensitive tool to assess changes in sensory function over time after incomplete cervical SCI.

Discrepancies between clinical assessments of sensory function and electrical perceptual thresholds after incomplete chronic cervical spinal cord injury

Study Design

Prospective experimental.

Objectives

To compare sensory function as revealed by light touch and pin prick tests of the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) and the electrical perceptual threshold (EPT) exams in individuals with chronic incomplete cervical spinal cord injury (SCI).

Setting

Pittsburgh, United States.

Methods

EPT was tested using cutaneous electrical stimulation (0.5 ms pulse width, 3 Hz) in 32 healthy controls and in 17 participants with SCI over key points on dermatomes C2 to T4 on each side of the body. Light touch and pin prick ISNCSCI scores were tested at the same key dermatomes in SCI participants.

Results

In controls, EPT values were higher in older males (1.26±0.2 mA, mean±s.d.) compared with younger males (1.0±0.2 mA) and older females (0.9±0.2 mA), regardless of the dermatome and side tested. Fifteen out of seventeen SCI participants showed that the level of sensory impairment detected by the EPT was below the level detected by the ISNCSCI (mean=4.5±2.4, range 1–9). The frequency distribution of EPTs was similar to older male controls in dermatomes above but not below the ISNCSCI sensory level. The difference between EPT and ISNCSCI sensory level was negatively correlated with the time post injury.

Conclusions

The results show that, in the chronic stage of cervical SCI, the EPT reveals spared sensory function at lower (~5) spinal segments than the ISNCSCI sensory exam. It is hence found that the EPT is a sensitive tool to assess recovery of sensory function after chronic SCI.

Spinal cord injury: how can we improve the classification and quantification of its severity and prognosis?

The preservation of functional neural tissue after spinal cord injury (SCI) is the basis for spontaneous neurological recovery. Some injured patients in the acute phase have more potential for recovery than others. This fact is problematic for the construction of clinical trials because enrollment of subjects with variable recovery potential makes it difficult to detect effects, requires large sample sizes, and risks Type II errors. In addition, the current methods to assess injury and recovery are non-quantitative and not sensitive. It is likely that therapeutic combinations will be necessary to cause substantially improved function after SCI, thus we need highly sensitive techniques to evaluate changes in motor, sensory, autonomic and other functions. We review several emerging neurophysiological techniques with high sensitivity. Quantitative methods to evaluate residual tissue sparing after severe acute SCI have not entered widespread clinical use. This reduces the ability to correlate structural preservation with clinical outcome following SCI resulting in enrollment of subjects with varying patterns of tissue preservation and injury into clinical trials. We propose that the inclusion of additional measures of injury severity, pattern, and individual genetic characteristics may enable stratification in clinical trials to make the testing of therapeutic interventions more effective and efficient. New imaging techniques to assess tract injury and demyelination and methods to quantify tissue injury, inflammatory markers, and neuroglial biochemical changes may improve the evaluation of injury severity, and the correlation with neurological outcome, and measure the effects of treatment more robustly than is currently possible. The ability to test such a multimodality approach will require a high degree of collaboration between clinical and research centers and government research support. When the most informative of these assessments is determined, it may be possible to identify patients with substantial recovery potential, improve selection criteria and conduct more efficient clinical trials.

Reliability of the electrical perceptual threshold and Semmes-Weinstein monofilament tests of cutaneous sensibility

STUDY DESIGN

Prospective experimental.

OBJECTIVES

To compare the reliability and repeatability of the electrical perceptual threshold (EPT) and Semmes-Weinstein monofilament (SWM) tests for cutaneous sensibility. EPT and SWM tests have potential as quantitative and sensitive adjuncts to the American Spinal Injuries Association (ASIA) Impairment Scale (AIS) assessment of spinal cord injury (SCI).

SETTING

London, UK.

METHODS

EPT and SWM tests were carried out on 40 neurologically healthy individuals (20 male). One examiner carried out all the tests. Each individual was examined for EPT and SWM sensitivity at ASIA key points on four dermatomes (C4, T1, T6, L4) on both sides of the body. The tests were repeated after an interval of approximately 1 week. Intra-rater reliability was determined using intra-class correlation coefficients (ICC). Repeatability was determined using the method of Bland and Altman.

RESULTS

There were no significant differences in the mean values of EPT or SWM between assessments for any dermatome. Significant difference in mean values for both EPT and SWM were observed between some dermatomes. ICC ranged from 0.67 to 0.81 for the EPT and from 0.46 to 0.61 for the SWM. Higher ICC for the EPT compared with the SWM was again revealed when male and female subjects were assessed separately. Correlation between EPT and SWM was weak or (largely) absent.

CONCLUSION

EPT has better reliability than SWM in healthy subjects. However, as both tests have the potential to add sensitivity and resolution to the AIS assessment, a further comparison of their repeatability in SCI is warranted.

Comparison of the data classification approaches to diagnose spinal cord injury

In our previous study, we have demonstrated that analyzing the skin impedances measured along the key points of the dermatomes might be a useful supplementary technique to enhance the diagnosis of spinal cord injury (SCI), especially for unconscious and noncooperative patients. Initially, in order to distinguish between the skin impedances of control group and patients, artificial neural networks (ANNs) were used as the main data classification approach. However, in the present study, we have proposed two more data classification approaches, that is, support vector machine (SVM) and hierarchical cluster tree analysis (HCTA), which improved the classification rate and also the overall performance. A comparison of the performance of these three methods in classifying traumatic SCI patients and controls was presented. The classification results indicated that dendrogram analysis based on HCTA algorithm and SVM achieved higher recognition accuracies compared to ANN. HCTA and SVM algorithms improved the classification rate and also the overall performance of SCI diagnosis.

Clinical neurophysiology in the prognosis and monitoring of traumatic spinal cord injury

Preclinical studies for the repair of spinal cord injury (SCI) and potential therapies for accessing the inherent plasticity of the central nervous system (CNS) to promote recovery of function are currently moving into the translational stage. These emerging clinical trials of therapeutic interventions for the repair of SCI require improved assessment techniques and quantitative outcome measures to supplement the American Spinal Injuries Association (ASIA) Impairment Scales. This chapter attempts to identify those electrophysiological techniques that show the most promise for provision of objective and quantitative measures of sensory, motor, and autonomic function in SCI. Reviewed are: (1) somatosensory evoked potentials, including dermatomal somatosensory evoked potentials, and the electrical perceptual threshold as tests of the dorsal (posterior) column pathway; (2) laser evoked potentials and contact heat evoked potentials as tests of the anterior spinothalamic tract; (3) motor evoked potentials in limb muscles, in response to transcranial magnetic stimulation of the motor cortex as tests of the corticospinal tract, and the application of the technique to assessment of trunk and sphincter muscles; and (4) the sympathetic skin response as a test of spinal cord access to the sympathetic chain.

Changes in Electrical Perception Threshold Within the First 6 Months After Traumatic Spinal Cord Injury

Objective. To assess the reliability of the electrical perception threshold (EPT) in healthy participants and its responsiveness in patients for 6 months after traumatic spinal cord injury (SCI). Methods. The reliability of EPT measures was assessed in 15 healthy volunteers (from C3 to S2). EPT measures were assessed in 37 patients at 1, 3, and 6 months after SCI. EPT was determined in dermatomes at, above, and below the neurological level of lesion. Reliability was quantified with an intraclass correlation coefficient (ICC) and responsiveness with the standardized response mean (SRM). Dermatomes were classified as having normal or pathological sensory perception, based on both light touch (LT) and EPT testing. The percentage of agreement between LT and EPT classifications was determined. Results. The ICCs varied considerably between dermatomes (0.00 ≤ ICC ≤ 0.86). Overall, EPTs changed little within the first 6 months after SCI, resulting in small SRM values. Agreement between classifications according to EPT or LT testing varied from 30% to 100%. The least agreement was observed in the first segment below the lesion. Conclusion. Future studies must note that the reliability of EPT differs between dermatomes in healthy participants. Furthermore, at and below the level of the lesion, spontaneous recovery of sensory perception is poor within the first 6 months after SCI. Based on subgroup analyses, if a translational trial aims to improve sensory perception around the level of the lesion, sensory-incomplete tetraplegic patients could be included. These patients show poor spontaneous recovery, and the EPT may detect subtle changes in perception.

Changes in electrical perceptual threshold in the first 6 months following spinal cord injury

OBJECTIVES

To investigate the use of electrical perceptual threshold (EPT) testing to follow the natural history of sensory progression after complete and incomplete acute spinal cord injury (SCI) and to compare EPT changes with the American Spinal Injuries Association (ASIA) Impairment Scale (AIS).

STUDY DESIGN

Prospective descriptive study.

METHODS

ASIA examination and EPT testing was performed on 17 patients (7 AIS A, 10 AIS B-D), within 1, 3, and 6 months after acute SCI. EPT assessment was carried out bilaterally at ASIA sensory points from 2 levels above the neurological level to all levels below, including the sacral segments. Comparisons of EPT values above, at, and below the SCI were made at the three time points as well as comparisons of EPT data to ASIA assessment.

RESULTS

There was poor agreement between lowest normal level on EPT and ASIA assessment. Over time, EPTs tended to deteriorate above and at the ASIA level in AIS A patients with modest changes below the neurological level of injury (NLI), mainly where EPTs correlated with the zone of partial preservation. Sacral sparing was detected in one patient with EPT testing, but not with ASIA assessment. AIS B-D patients showed improvement at the ASIA level and extensive changes, both improvement and deterioration, below the NLI.

CONCLUSION

EPT testing has sufficient sensitivity to detect subclinical changes in sensory function as early as the first month post-SCI, which is not apparent in ASIA examination. In particular, the testing is able to show abnormalities at and around the injury site for both complete and incomplete SCI. In addition, EPT allows for the detection and monitoring of alterations, both improvements and deterioration, in the abnormal range of sensation.

Action of 5 Hz repetitive transcranial magnetic stimulation on sensory, motor and autonomic function in human spinal cord injury

OBJECTIVE

To assess the effectiveness of physiological outcome measures in detecting functional change in the degree of impairment of spinal cord injury (SCI) following repetitive transcranial magnetic stimulation (rTMS) of the sensorimotor cortex.

METHODS

Subjects with complete or incomplete cervical (or T1) SCI received real and sham rTMS in a randomised placebo-controlled single-blinded cross-over trial. rTMS at sub-threshold intensity for upper-limb muscles was applied (5 Hz, 900 stimuli) on 5 consecutive days. Assessments made before and for 2 weeks after treatment comprised the ASIA (American Spinal Injuries Association) impairment scale (AIS), the Action Research Arm Test (ARAT), a peg-board test, electrical perceptual test (EPT), motor evoked potentials, cortical silent period, cardiovascular and sympathetic skin responses.

RESULTS

There were no significant differences in AIS outcomes between real and sham rTMS. The ARAT was increased at 1h after real rTMS compared to baseline. Active motor threshold for the most caudally innervated hand muscle was increased at 72 and 120 h compared to baseline. Persistent reductions in EPT to rTMS occurred in two individuals.

CONCLUSIONS

Changes in cortical motor threshold measures may accompany functional gains to rTMS in SCI subjects.

SIGNIFICANCE

Electrophysiological measures may provide a useful adjunct to ASIA impairment scales.

An initial exploration of the perceptual threshold test using electrical stimulation to measure arm sensation following stroke

Objective: To explore the viability of the perceptual threshold test using electrical stimulation to measure light touch sensation in the hands of stroke survivors.

Design: Descriptive study.

Setting: University research laboratory.

Subjects: Twenty-nine adult community-dwelling chronic stroke survivors.

Main measure(s): Perceptual threshold test using electrical stimulation, stroke rehabilitation assessment of movement, Nottingham sensory assessment for stereognosis, action research arm test, Fugl-Meyer assessment of sensation and motor activity log 14.

Results: Perceptual threshold test using electrical stimulation mean threshold values were 1.23 (0.6) milliamperes (range 0.5–3.5) for the uninvolved side and 1.68 (0.91) milliamperes (range 0.5–4.5) for the involved side. The perceptual threshold test using electrical stimulation demonstrated excellent intra-rater reliability (intraclass correlation coefficient = 0.896 – uninvolved; 0.829 – involved). There was a statistically significant difference between the perceptual threshold test using electrical stimulation mean threshold values for the uninvolved and involved arms ( P = 0.003), but this significance did not hold for subjects who had normal sensation as measured by the Fugl-Meyer assessment of sensation ( P = 0.083). Low to nonexistent correlations were found between the perceptual threshold test using electrical stimulation and other measures of sensation, arm movement, activity and participation.

Conclusions: The perceptual threshold test using electrical stimulation is a reliable and clinically feasible test with the potential to identify sensory capacity in stroke survivors with substantial sensory loss. Electrical sensory thresholds do not reflect overall sensory function or motor capabilities in stroke survivors.

Characterization of neurological recovery following traumatic sensorimotor complete thoracic spinal cord injury

STUDY DESIGN

Retrospective, longitudinal analysis of sensory, motor and functional outcomes from individuals with thoracic (T2-T12) sensorimotor complete spinal cord injury (SCI).

OBJECTIVES

To characterize neurological changes over the first year after traumatic thoracic sensorimotor complete SCI.

METHODS

A dataset of 399 thoracic complete SCI subjects from the European Multi-center study about SCI (EMSCI) was examined for neurological level, sensory levels and sensory scores (pin-prick and light touch), lower extremity motor score (LEMS), ASIA Impairment Scale (AIS) grade, and Spinal Cord Independence Measure (SCIM) over the first year after SCI.

RESULTS

AIS grade conversions were limited. Sensory scores exhibited minimal mean change, but high variability in both rostral and caudal directions. Pin-prick and light touch sensory levels, as well as neurological level, exhibited minor changes (improvement or deterioration), but most subjects remained within one segment of their initial injury level after 1 year. Recovery of LEMS occurred predominantly in subjects with low thoracic SCI. The sensory zone of partial preservation (ZPP) had no prognostic value for subsequent recovery of sensory levels or LEMS. However, after mid or low thoracic SCI, ≥3 segments of sensory ZPP correlated with an increased likelihood for AIS grade conversion.

CONCLUSION

The data suggest that a sustained deterioration of three or more thoracic sensory levels or loss of upper extremity motor function are rare events and may be useful for tracking the safety of a therapeutic intervention in early phase acute SCI clinical trials, if a significant proportion of study subjects exhibit such an ascent.

Age, gender, and side differences of cutaneous electrical perceptual threshold testing in an able-bodied population

OBJECTIVE

To investigate age, gender, and left-right differences in cutaneous electrical perceptual threshold (EPT) testing in an able-bodied, Australian sample.

STUDY DESIGN

Prospective experimental.

SETTING

Hospital-based spinal cord injuries unit.

METHODS

Cutaneous electrical stimulation of the 28 dermatomes at ASIA sensory key points (C2-S4/S5) was performed on 29 female and 16 male healthy volunteers aged 21 to 76 years. Mean EPTs for each dermatome were compared (repeated measures ANOVA) for left-right, gender-related, and age-related (</ >50 years of age) differences.

RESULTS

There was no group difference between sides (repeated measures ANOVA, P = 0.934). Women across all ages had lower group mean EPTs than men (P < 0.0001). Women younger than age 50 years had lower mean EPTs than those older than age 50 years (P = 0.008). There was no group difference between younger and older men (P = 0.371). Analysis of individual dermatomes revealed no significant differences in thoracic dermatomes between genders or age groups, contrary to the limb dermatomes.

CONCLUSION

There were gender differences in EPT values across all ages. Women had higher EPTs as they advanced in age, but this was less clear in men. There was considerable somatotopic variability in EPTs, especially in the lower limbs. If EPT testing is to be applied to detect subclinical changes within a dermatome, establishment of age- and gender-specific somatotopic normograms is a prerequisite.

Dermatomal Somatosensory Evoked Potentials and Electrical Perception Thresholds During Recovery From Cervical Spinal Cord Injury

Background. Dermatomal somatosensory evoked potentials (dSSEPs) not only provide a neurophysiological readout comparable with conventional SSEPs but also provide an opportunity to track changes in sensory function corresponding to individual dermatomes (ie, a single spinal segment) above, at, and below the level of spinal cord injury (SCI). Objectives. This study aimed to determine the reliability and responsiveness of dSSEPs and electrical perception thresholds (EPTs) to monitor changes in sensory function after cervical SCI. Methods. Initial and follow-up dSSEPs and EPTs were recorded from cervical dermatomes (C4-C8) of patients with traumatic tetraplegia (C3-C8; ASIA Impairment Scale A-D) during recovery after SCI (n = 18). Results. Follow-up examination of 74 initial dSSEPs unaffected by SCI (n = 18) revealed no significant change in latency (Δ = 0.0 ± 1.4 ms; P = .9) or EPT sensitivity (Δ = 0.1 ± 0.8 mA; P = .3). In 41 dSSEPs initially delayed after SCI (n = 14), latencies significantly decreased on follow-up examination (Δ = -3.1 ± 2.9 ms; P < .01) without a corresponding increase in sensitivity of the EPT (Δ = 0.2 ± 3.4 mA; P = .7). dSSEPs that were not measurable initially were subsequently recorded in 11 dermatomes (n = 5) on follow-up examination. This conversion of abolished-to-recordable dSSEPs was often preceded by the perception of an initial EPT and associated with a concomitant recovery of EPT at follow-up. Conclusion. dSSEPs and EPT can be reliably recorded to monitor changes in sensory function for each individual spinal segment after cervical SCI. dSSEPs may be potentially useful to monitor the safety of a therapeutic drug or cell transplant in early-phase (I/II) clinical trials as well as document the potential efficacy of interventions where the standard neurological assessment might not detect subtle therapeutic effects.

Outcome measures in spinal cord injury: recent assessments and recommendations for future directions

STUDY DESIGN

Review by the spinal cord outcomes partnership endeavor (SCOPE), which is a broad-based international consortium of scientists and clinical researchers representing academic institutions, industry, government agencies, not-for-profit organizations and foundations.

OBJECTIVES

Assessment of current and evolving tools for evaluating human spinal cord injury (SCI) outcomes for both clinical diagnosis and clinical research studies.

METHODS

a framework for the appraisal of evidence of metric properties was used to examine outcome tools or tests for accuracy, sensitivity, reliability and validity for human SCI.

RESULTS

Imaging, neurological, functional, autonomic, sexual health, bladder/bowel, pain and psychosocial tools were evaluated. Several specific tools for human SCI studies have or are being developed to allow the more accurate determination for a clinically meaningful benefit (improvement in functional outcome or quality of life) being achieved as a result of a therapeutic intervention.

CONCLUSION

Significant progress has been made, but further validation studies are required to identify the most appropriate tools for specific targets in a human SCI study or clinical trial.

A quantitative skin impedance test to diagnose spinal cord injury

The purpose of this study was to develop a quantitative skin impedance test that could be used to diagnose spinal cord injury (SCI) if any, especially in unconscious and/or non-cooperative SCI patients. To achieve this goal, initially skin impedance of the sensory key points of the dermatomes (between C3 and S1 bilaterally) was measured in 15 traumatic SCI patients (13 paraplegics and 2 tetraplegics) and 15 control subjects. In order to classify impedance values and to observe whether there would be a significant difference between patient and subject impedances, an artificial neural network (ANN) with back-propagation algorithm was employed. Validation results of the ANN showed promising performance. It could classify traumatic SCI patients with a success rate of 73%. By assessing the experimental protocols and the validation results, the proposed method seemed to be a simple, objective, quantitative, non-invasive and non-expensive way of assessing SCI in such patients.

Neuropathic pain in spinal cord injury: significance of clinical and electrophysiological measures

A large percentage of spinal cord-injured subjects suffer from neuropathic pain below the level of the lesion (bNP). The neural mechanisms underlying this condition are not clear. The aim of this study was to elucidate the general effects of spinal deafferentiation and of bNP on electroencephalographic (EEG) activity. In addition, the relationship between the presence of bNP and impaired function of the spinothalamic tract was studied. Measurements were performed in complete and incomplete spinal cord-injured subjects with and without bNP as well as in a healthy control group. Spinothalamic tract function, assessed by contact heat evoked potentials, did not differ between subjects with and without bNP; nevertheless, it was impaired in 94% of subjects suffering from bNP. In the EEG recordings, the degree of deafferentiation was reflected in a slowing of EEG peak frequency in the 6-12-Hz band. Taking into account this unspecific effect, spinal cord-injured subjects with bNP showed significantly slower EEG activity than subjects without bNP. A discrimination analysis in the subjects with spinothalamic tract dysfunction correctly classified 84% of subjects as belonging to either the group with bNP or the group without bNP, according to their EEG peak frequency. These findings could be helpful for both the development of an objective diagnosis of bNP and for testing the effectiveness of new therapeutic agents.

Electrophysiological outcomes after spinal cord injury

Electrophysiological measures can provide information that complements clinical assessments such as the American Spinal Injury Association sensory and motor scores in the evaluation of outcomes after spinal cord injury (SCI). The authors review and summarize the literature regarding tests that are most relevant to the study of SCI recovery--in particular, motor evoked potentials and somatosensory evoked potentials (SSEPs). In addition, they discuss the role of other tests, including F-wave nerve conductance tests and electromyography, sympathetic skin response, and the Hoffman reflex (H-reflex) test as well as the promise of dermatomal SSEPs and the electrical perceptual threshold test, newer quantitative tests of sensory function. It has been shown that motor evoked potential amplitudes improve with SCI recovery but latencies do not. Somatosensory evoked potentials are predictive of ambulatory capacity and hand function. Hoffman reflexes are present during spinal shock despite the loss of tendon reflexes, but their amplitudes increase with time after injury. Further, H-reflex modulation is reflective of changes in spinal excitability. While these tests have produced data that is congruent with clinical evaluations, they have yet to surpass clinical evaluations in predicting outcomes. Continuing research using these methodologies should yield a better understanding of the mechanisms behind SCI recovery and thus provide potentially greater predictive and evaluative power.

Electrical perceptual threshold testing: a validation study

BACKGROUND/OBJECTIVE

To investigate inter-rater and intra-rater reliability of electrical perceptual threshold (EPT) testing in assessing somatosensory function in healthy volunteers.

STUDY DESIGN

Prospective experimental.

SETTING

Hospital-based spinal cord injuries unit.

METHODS

Cutaneous electrical stimulation of 4 dermatomes at ASIA sensory key points (C3, T1, L3, and S2) was performed on 40 control subjects. The lowest ascending stimulus intensity at which sensation was perceived was recorded as the EPT. Mean EPT values for each dermatome, as determined by 2 testers at 2 time points, were examined and plotted against a normative template. Differences and associations between intra- and inter-rater measurements and left-right measurements were studied. EPT results for 2 people with spinal cord injuries were also examined.

RESULTS

EPT measurements from left and right sides, obtained from the 2 time points and 2 testers, were found to be strongly associated, with the exception of left and right side measurements at the S2 dermatome. No significant differences in the mean EPT for tester or time period were found. The intra- and inter-rater reliability was good for all dermatomes tested. Mean EPT measurements fell within the range of a normative template at each of the 4 dermatomes tested.

CONCLUSION

EPT is an objective, reproducible, and quantifiable method of assessing sensation in a control group. However, caution should be applied in certain dermatomes such as S2, where there was large variation between left and right side measurements.

Autologous olfactory ensheathing cell transplantation in human paraplegia: a 3-year clinical trial

Olfactory ensheathing cells show promise in preclinical animal models as a cell transplantation therapy for repair of the injured spinal cord. This is a report of a clinical trial of autologous transplantation of olfactory ensheathing cells into the spinal cord in six patients with complete, thoracic paraplegia. We previously reported on the methods of surgery and transplantation and the safety aspects of the trial 1 year after transplantation. Here we address the overall design of the trial and the safety of the procedure, assessed during a period of 3 years following the transplantation surgery. All patients were assessed at entry into the trial and regularly during the period of the trial. Clinical assessments included medical, psychosocial, radiological and neurological, as well as specialized tests of neurological and functional deficits (standard American Spinal Injury Association and Functional Independence Measure assessments). Quantitative test included neurophysiological tests of sensory and motor function below the level of injury. The trial was a Phase I/IIa design whose main aim was to test the feasibility and safety of transplantation of autologous olfactory ensheathing cells into the injured spinal cord in human paraplegia. The design included a control group who did not receive surgery, otherwise closely matched to the transplant recipient group. This group acted as a control for the assessors, who were blind to the treatment status of the patients. The control group also provided the opportunity for preliminary assessment of the efficacy of the transplantation. There were no adverse findings 3 years after autologous transplantation of olfactory ensheathing cells into spinal cords injured at least 2 years prior to transplantation. The magnetic resonance images (MRIs) at 3 years showed no change from preoperative MRIs or intervening MRIs at 1 and 2 years, with no evidence of any tumour of introduced cells and no development of post-traumatic syringomyelia or other adverse radiological findings. There were no significant functional changes in any patients and no neuropathic pain. In one transplant recipient, there was an improvement over 3 segments in light touch and pin prick sensitivity bilaterally, anteriorly and posteriorly. We conclude that transplantation of autologous olfactory ensheathing cells into the injured spinal cord is feasible and is safe up to 3 years of post-implantation, however, this conclusion should be considered preliminary because of the small number of trial patients.

Guidelines for the conduct of clinical trials for spinal cord injury (SCI) as developed by the ICCP panel: clinical trial outcome measures

An international panel reviewed the methodology for clinical trials of spinal cord injury (SCI), and provided recommendations for the valid conduct of future trials. This is the second of four papers. It examines clinical trial end points that have been used previously, reviews alternative outcome tools and identifies unmet needs for demonstrating the efficacy of an experimental intervention after SCI. The panel focused on outcome measures that are relevant to clinical trials of experimental cell-based and pharmaceutical drug treatments. Outcome measures are of three main classes: (1) those that provide an anatomical or neurological assessment for the connectivity of the spinal cord, (2) those that categorize a subject's functional ability to engage in activities of daily living, and (3) those that measure an individual's quality of life (QoL). The American Spinal Injury Association impairment scale forms the standard basis for measuring neurologic outcomes. Various electrophysiological measures and imaging tools are in development, which may provide more precise information on functional changes following treatment and/or the therapeutic action of experimental agents. When compared to appropriate controls, an improved functional outcome, in response to an experimental treatment, is the necessary goal of a clinical trial program. Several new functional outcome tools are being developed for measuring an individual's ability to engage in activities of daily living. Such clinical end points will need to be incorporated into Phase 2 and Phase 3 trials. QoL measures often do not correlate tightly with the above outcome tools, but may need to form part of Phase 3 trial measures.