Towards improved clinical and physiological assessments of recovery in spinal cord injury: a clinical initiative

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

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

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.

Progress on clinical characteristics and identification of location of thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is the most common cause for thoracic spinal stenosis. TOLF is usually complicated by thoracic disc herniation, ossification of the posterior longitudinal ligament and degenerative spinal diseases such as cervical spondylosis and lumbar spinal stenosis, and the ossification also usually has a discontinuous or continuous multi-segment distribution. The resultant superposition of several symptoms makes the clinical manifestations complex. Currently, the diagnosis of TOLF depends mainly on the patient's symptoms, physical examination and thoracic CT and MRI examinations. Identification of the location of TOLF depends more on the doctor's subjective judgement. Diagnostic problems are related to the specific region and level of surgical decompression: if the extent of decompression is insufficient, the treatment is inadequate, resulting in residual symptoms. Obversely, unnecessary trauma and a various complications will occur if the decompression is too extensive. Hence, the clinical features and process of diagnosis, especially the means of identifying the location, still require further improvement. It is necessary to establish a simple and accurate means of identifying the segment of TOLF that is responsible for the neurologic deficit: a number of spinal surgeons have been working hard on this. This article will provided an overview of the clinical features of TOLF and the related problems of clinical identification of the location of the segment causing the neurological deficit. The relationship between the imaging manifestations and clinical characteristics still need to be explored with the aim of establishing a simple and precise method for determining precisely whether TOLF is related to spinal cord injury or not, thus reducing surgical trauma and achieving an optimal prognosis.

Sympathetic skin responses and autonomic dysfunction in spinal cord injury

Sympathetic skin responses (SSRs), a measure of sympathetic cholinergic sudomotor function, have been used in the assessment of autonomic dysfunction in patients with spinal cord injury (SCI). This review highlights the basic mechanisms underlying SSRs as well as their application to the SCI population. We address the utility of SSRs in assessing autonomic function, the relationship between autonomic and sensorimotor impairment, and the association between SSRs and the sequelae of autonomic dysfunction in SCI, particularly autonomic dysreflexia and orthostatic hypotension. Overall, SSRs are a rapid, convenient and non-invasive method illustrating that the severity of autonomic impairment can be independent from sensorimotor impairment. We suggest that SSRs be used in conjunction with other validated autonomic tests in order to predict or document autonomic dysfunction in SCI.

Disordered cardiovascular control after spinal cord injury

Damage to the spinal cord disrupts autonomic pathways, perturbing cardiovascular homeostasis. Cardiovascular dysfunction increases with higher levels of injury and greater severity. Disordered blood pressure control after spinal cord injury (SCI) has significant ramifications as cord-injured people have an increased risk of developing heart disease and stroke; cardiovascular dysfunction is currently a leading cause of death among those with SCI. Despite the clinical significance of abnormal cardiovascular control following SCI, this problem has been generally neglected by both the clinical and research community. Both autonomic dysreflexia and orthostatic hypotension are known to prevent and delay rehabilitation, and significantly impair the overall quality of life after SCI. Starting with neurogenic shock immediately after a higher SCI, ensuing cardiovascular dysfunctions include orthostatic hypotension, autonomic dysreflexia and cardiac arrhythmias. Disordered temperature regulation accompanies these autonomic dysfunctions. This chapter reviews the human and animal studies that have furthered our understanding of the pathophysiology and mechanisms of orthostatic hypotension, autonomic dysreflexia and cardiac arrhythmias. The cardiovascular dysfunction that occurs during sexual function and exercise is elaborated. New awareness of cardiovascular dysfunction after SCI has led to progress toward inclusion of this important autonomic problem in the overall assessment of the neurological condition of cord-injured people.

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.

Quantifying lower limb joint position sense using a robotic exoskeleton: a pilot study

Clinicians and scientists often focus on tracking the recovery of motor skills after spinal cord injury (SCI), but less attention is paid to the recovery of sensory skills. Measures of sensory function are imperative for evaluating the efficacy of treatments and therapies. Proprioception is one sensory modality that provides information about static position and movement sense. Because of its critical contribution to motor control, proprioception should be measured during the course of recovery after neurological injury. Current clinical methods to test proprioception are limited to crude, manual tests of movement and position sense. The purpose of this study was to develop a quantitative assessment tool to measure joint position sense in the legs. We used the Lokomat, a robotic exoskeleton, and custom software to assess joint position sense in the hip and knee in 9 able-bodied (AB) subjects and 1 person with incomplete SCI. We used two different test paradigms. Both required the subject to move the leg to a target angle, but the presentation of the target was either a remembered or visual target angle. We found that AB subjects had more accurate position sense in the remembered task than in the visual task, and that they tended to have greater accuracy at the hip than at the knee. Position sense of the subject with SCI was comparable to those of the AB subjects. We show that using the Lokomat to assess joint position sense may be an effective clinical measurement tool.

Using sympathetic skin responses in individuals with spinal cord injury as a quantitative evaluation of motor imagery abilities

BACKGROUND

Motor imagery (MI) ability should be evaluated in selected individuals with spinal cord injury (SCI) who can benefit from MI training in their rehabilitation program. Electrodermal activity seems to be a reliable indicator for assessing MI ability. However, individuals with SCI have a variety of autonomic dysfunctions.

OBJECTIVE

This study aimed to investigate electrodermal responses (EDRs) elicited by MI.

DESIGN

A cost-utility analysis of EDR above and below the lesion level in individuals with complete or incomplete SCI (n = 30) versus a control group of individuals who were healthy (n = 10) was used.

METHOD

The EDR was recorded above and below the lesion level during MI of a drinking action. Duration, latency, and amplitude of EDR were the outcome measures.

RESULTS

Hand and foot EDR in the control group occurred with the same pattern and similar latencies, suggesting a common efferent sympathetic pathway to sweat glands of the hand and foot mediating a sympathetic skin response. Individuals with SCI elicited responses above the lesion level. The EDR amplitude was correlated to the lesion level and autonomic dysreflexia history. No foot response was recorded in individuals with complete cervical and thoracic motor lesions. Foot response with a lower amplitude and higher latency occurred in participants with incomplete motor lesion, suggesting a link between the descending motor pathway and sympathetic function.

LIMITATIONS

The small sample of individuals with incomplete SCI limits the generalization of the results obtained at the foot site.

CONCLUSIONS

Electrodermal response above the lesion level may be a reliable index for assessing MI ability in individuals with SCI. It is a noninvasive, user-friendly method for clinicians to consider before enrolling individuals in MI training.

Refined sensory measures of neural repair in human spinal cord injury: bridging preclinical findings to clinical value

Sensory input from the periphery to the brain can be severely compromised or completely abolished after an injury to the spinal cord. Evidence from animal models suggests that endogenous repair processes in the spinal cord mediate extensive sprouting and that this might be further attenuated by targeted therapeutic interventions. However, the extent to which sprouting can contribute to spontaneous recovery after human spinal cord injury (SCI) remains largely unknown, in part because few measurement tools are available in order to non-invasively detect subtle changes in neurophysiology. The proposed application of segmental sensory evoked potentials (e.g., dermatomal contact heat evoked potentials and somatosensory evoked potentials) to assess conduction in ascending pathways (i.e., spinothalamic and dorsal column, respectively) differs from conventional approaches in that individual spinal segments adjacent to the level of lesion are examined. The adoption of these approaches into clinical research might provide improved resolution for measuring changes in sensory impairments and might determine the extent by which spontaneous recovery after SCI is mediated by similar endogenous repair mechanisms in humans as in animal models.

Restorative neurology: consideration of the new anatomy and physiology of the injured nervous system

The adult human nervous system is an incredibly complex set of thousands to tens of thousands of connections between a hundred billion neurons that develops via an intricate spatial-temporal process and is shaped by experience. In addition, any one anatomical arrangement of neural circuits is usually capable of multiple physiological states. Following neurological injury, a new anatomy, and consequently a new spectrum of physiology, emerges within this nervous system with its mix of both injured and uninjured parts. It is this new combination of neural components that determines the extent to which natural functional recovery can occur and the extent to which clinical interventions can further that recovery. Detecting the new anatomy and physiology of the injured human nervous system is difficult but not impossible and some methods can track over time changes in neural structure or, more often, functions that correlate with neurological improvement. The goal of restorative neurology is to make best use of this new anatomy and physiology to facilitate neurological recovery. While we are still learning about how neurorehabilitation interventions generate functional recovery, we can begin to test hypothesis regarding the underlying mechanisms of neural plasticity and attempt to augment those processes.

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.

Neurophysiological evaluation of segmental motor neuron function of the thoracic cord in chronic SCI

STUDY DESIGN

Pilot study.

OBJECTIVES

The aim of the study was to develop a neurophysiological method to diagnose the cranial as well as the caudal level of a complete thoracic spinal cord injury (SCI) with higher precision than today's protocols.

SETTING

SCI unit Karolinska University Hospital, Stockholm, Sweden.

METHODS

Bipolar needle electromyography was recorded in intercostal spaces of five patients with chronic, complete thoracic SCI. Tests were performed during rest, during voluntary activation and during activation of lower body spasticity. Magnetic resonance imaging (MRI) was performed in each patient according to a protocol optimized for imaging near metal implants.

RESULTS

Three distinct patterns were found in each patient. Above the lesion we found voluntary activated, normal motor unit potentials (MUPs). At the neurological level and a varying number of segments below, denervated intercostal segments with fibrillation potentials and positive sharp waves appeared. Below the neurological level, normal MUP activated in concert with lower body spasticity was found. The number of denervated segments showed a significant correlation to the length of spinal cord discontinuity on MRI (r=0.97, P<0.05).

CONCLUSION

Intercostal neurophysiology in combination with MRI optimized for imaging near metal implants can be used to determine the extent of a chronic complete thoracic SCI, both anatomically and functionally. The described method increases the sensitivity to detect delicate neurological changes related to the dynamic of the pathology that follows SCI and may be useful in analyzing outcome in clinical trials.

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.

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.

Human motor evoked potential responses following spinal cord transection: an in vivo study

Motor evoked potential (MEP) monitoring has been used increasingly in conjunction with somatosensory evoked potential monitoring to monitor neurological changes during complex spinal operations. No published report has demonstrated the effects of segmental spinal cord transection on MEP monitoring.

The authors describe the case of an 11-year-old girl with lumbar myelomeningocele and worsening thoracolumbar scoliosis who underwent a T11–L5 fusion and spinal transection to prevent tethering. Intraoperative MEP and somatosensory evoked potential monitoring were performed, and the spinal cord was transected in 4 quadrants. The MEPs were lost unilaterally as each anterior quadrant was sectioned.

This is the first reported case that demonstrates the link between spinal cord transection and MEP signaling characteristics. Furthermore, it demonstrates the relatively minor input of the ipsilateral ventral corticospinal tract in MEP physiology at the thoracolumbar junction. Finally, this study further supports the use of MEPs as a specific intraoperative neuromonitoring tool.

Impaired transmission in the corticospinal tract and gait disability in spinal cord injured persons

Rehabilitation following spinal cord injury is likely to depend on recovery of corticospinal systems. Here we investigate whether transmission in the corticospinal tract may explain foot drop (inability to dorsiflex ankle) in persons with spinal cord lesion. The study was performed in 24 persons with incomplete spinal cord lesion (C1 to L1) and 15 healthy controls. Coherence in the 10- to 20-Hz frequency band between paired tibialis anterior muscle (TA) electromyographic recordings obtained in the swing phase of walking, which was taken as a measure of motor unit synchronization. It was significantly correlated with the degree of foot drop, as measured by toe elevation and ankle angle excursion in the first part of swing. Transcranial magnetic stimulation was used to elicit motor-evoked potentials (MEPs) in the TA. The amplitude of the MEPs at rest and their latency during contraction were correlated to the degree of foot drop. Spinal cord injured participants who exhibited a large foot drop had little or no MEP at rest in the TA muscle and had little or no coherence in the same muscle during walking. Gait speed was correlated to foot drop, and was the lowest in participants with no MEP at rest. The data confirm that transmission in the corticospinal tract is of importance for lifting the foot during the swing phase of human gait.

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.

Ankle paresis in incomplete spinal cord injury: relation to corticospinal conductivity and ambulatory capacity

There is limited data on the relation of corticospinal tract conductivity to clinical measures in incomplete spinal cord injury. This study examined the relationship of muscle strength to corticospinal tract input assessed by motor evoked potentials (MEPs) during static and dynamic conditions and to gait. Dorsiflexor strength was established by manual muscle test, maximal voluntary contraction, and maximal movement velocity, the latter being acquired during auditory-paced ankle movements. MEPs were elicited during isometric contractions with constant or continuously increasing ankle joint torque. Gait was assessed by quantifying its speed and independence. Linear regression analyses showed that maximal movement velocity was related to the MEP latencies and amplitudes in the dynamic condition (R(2)(adj.) = 0.62) and to the MEP latencies in the static condition (R(2)(adj.) = 0.45). Maximal voluntary contraction was only related to the MEP latencies in the static (R(2)(adj.) = 0.45) and the dynamic condition (R(2)(adj.) = 0.21), whereas manual muscle test did not show any relationship to the MEPs. In incomplete spinal cord injury patients, the dynamic measure maximal movement velocity might be a useful clinical assessment of corticospinal tract function. Clinical studies on recovery and repair of corticospinal tract function in spinal lesions could substantially benefit from implementing dynamic measures in the clinical assessment protocol.

Recovery from a spinal cord injury: significance of compensation, neural plasticity, and repair

Clinical recovery after a lesion of the central nervous system (CNS) can be attributed to mechanisms of functional compensation, neural plasticity, and/or repair. The relative impact of each of these mechanisms after a human spinal cord injury (SCI) has been explored in a prospective European multi-center study in 460 acute traumatic SCI subjects. Functional (activities of daily living and ambulatory capacity), neurological (sensory-motor deficits), and spinal conductivity (motor- and somato-sensory evoked potentials) measures were repeatedly followed over 12 months. In accordance with previous studies, complete SCI subjects (cSCI; n = 217) improved in activities of daily living unrelated to changes of the neurological condition, while incomplete SCI subjects (iSCI; n = 243) showed a greater functional and neurological recovery. The functional recovery in iSCI subjects was not related to an improvement of spinal conductivity, as reflected in unchanged latencies of the evoked potentials. This is in line with animal studies, where spinal conductivity of damaged spinal tracts has been reported to remain unchanged. These findings support the assumption that functional recovery occurs by compensation, especially in cSCI and by neural plasticity leading to a greater improvement in iSCI. Relevant repair of damaged spinal pathways does not take place.

Cortical control of erector spinae muscles during arm abduction in humans

Abduction of one arm preferentially activates erector spinae muscles on the other side to stabilise the body. We hypothesise that the corticospinal drive to the arm abductors and the erector spinae may originate from the same hemisphere. In 18 subjects, transcranial magnetic stimulation (TMS) was applied using an angle double-cone coil placed symmetrically over the vertex. Motor evoked potentials (MEP) could not be evoked systematically seated at rest but could be evoked bilaterally in erector spinae muscles during unilateral arm abduction. TMS was applied at 110% and 120% motor threshold (MT) for the contralateral erector spinae muscle when an arm was abducted against resistance. The electromyographic (EMG) activity in the erector spinae at L4 vertebral level during contralateral arm abduction was significantly higher (P<0.05) than in the ipsilateral erector spinae. The mean (+/-S.E.M.) latencies of MEPs in the contralateral muscle to TMS at 120%MT (left 16.0+/-0.8 ms; right 17.0+/-0.8 ms) were significantly (P<0.05) longer than in the ipsilateral erector spinae (13.9+/-1.0 ms; 16.6+/-0.4 ms). In two of six subjects from the same group, it was possible to elicit MEPs by TMS applied selectively to one hemisphere using a figure-of-eight coil. MEPs ipsilateral to the TMS had longer latencies than contralateral MEPs. The study revealed an unexpectedly longer rather than shorter latency of the MEP recorded from the lumbar erector spinae muscles when co-activated during abduction of the opposite arm. A speculative explanation is that TMS might activate back muscles contralateral to arm abduction via an uncrossed, ipsilateral corticospinal tract that is slower conducting than the conventional crossed corticospinal tract. The study has implications for the design of measures to promote recovery and rehabilitation of motor function in disorders such as stroke and spinal cord injury.

Inter-rater reliability of motor and sensory examinations performed according to American Spinal Injury Association standards

STUDY DESIGN

Prospective observational.

AIM

To examine inter-rater reliability of motor and sensory examinations performed according to American Spinal Injury Association (ASIA) standards.

SETTING

National Spinal Injuries Centre, Stoke Mandeville Hospital, Buckinghamshire Hospitals NHS Trust, UK.

MATERIAL AND METHOD

Results of ASIA motor and sensory examinations performed by two experienced examiners on 45 patients with spinal cord injury (SCI) were compared.

RESULTS

Total ASIA scores showed very strong correlation between the two examiners, with Pearson correlation coefficients and intraclass correlation coefficients exceeding 0.96, P<0.01 for total motor, light touch and pin prick scores. The agreement for individual muscle testing of the 10 ASIA key muscles showed substantial agreement for majority of muscles, with the weighted Kappa coefficient range 0.649-0.993, P<0.05. The overall agreement in assignment of manual muscle testing grades (0-5) was 82% on the right and 84% on the left, with the strongest agreement for grade '0' and the weakest for grade '3'. The unweighted Kappa coefficient for agreement in motor and sensory levels ranged from 0.68 to 0.78 (P<0.01). There was no difference in ASIA impairment grades derived from the two examiners' results.

CONCLUSIONS

Our study results showed very good levels of agreement in ASIA clinical examinations between two experienced examiners. The established degree of variability due to inter-rater differences should be taken into account in study design of clinical trials with more than one assessor..

Fighting for each segment: estimating the clinical value of cervical and thoracic segments in SCI

Patients suffering from complete spinal cord injury (SCI) are the most likely candidates for the application of new interventions for neural repair and regeneration. It is assumed that some of these treatments will have their strongest impact at the segmental level. Therefore, it is important to evaluate the clinical relevance of potential changes at the segmental levels concerning both improvement and deterioration. Data of 98 motor complete SCI patients were derived from the European Multicenter Study of Human Spinal Cord Injury database. Six months after injury, the ASIA motor score and Spinal Cord Independence Measure (SCIM) were assessed as dependent variables (linear regression analysis) to disclose the difference between each segment. Separate analyses using linear regression for tetraplegic patients (n = 39) and paraplegic patients with thoracic lesions (n = 54) were performed to calculate the difference between each spinal segment. In tetraplegic patients, both the ASIA motor score and the SCIM revealed relevant differences per spinal segment (9 and 4 points, respectively) while in paraplegic patients there was no difference for the SCIM and the ASIA motor score between T2 and T8. We suggest that in complete tetraplegic patients, changes of even one spinal segment will either improve or degrade both motor function and independence. Segmental changes at the thoracic level are not assessable by the ASIA motor score and SCIM tests. Therefore, the assessment of efficacy and safety in thoracic patients by these two tests has limited value when applied to cervical SCI. These findings may be considered in clinical trials for the evaluation of beneficial effects and risk management when treating patients with spinal cord injury.

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.

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP Panel: clinical trial inclusion/exclusion criteria and ethics

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the third of four papers. It examines inclusion and exclusion criteria that can influence the design and analysis of clinical trials in SCI, together with confounding variables and ethical considerations. Inclusion and exclusion criteria for clinical trials should consider several factors. Among these are (1) the enrollment of subjects at appropriate stages after SCI, where there is supporting data from animal models or previous human studies; (2) the severity, level, type, or size of the cord injury, which can influence spontaneous recovery rate and likelihood that an experimental treatment will clinically benefit the subject; and (3) the confounding effects of various independent variables such as pre-existing or concomitant medical conditions, other medications, surgical interventions, and rehabilitation regimens. An issue of substantial importance in the design of clinical trials for SCI is the inclusion of blinded assessments and sham surgery controls: every effort should be made to address these major issues prospectively and carefully, if clear and objective information is to be gained from a clinical trial. The highest ethical standards must be respected in the performance of clinical trials, including the adequacy and clarity of informed consent.

REVIEW OF TREATMENT TRIALS IN HUMANSPINAL CORD INJURY

OBJECTIVE

To provide a comprehensive review of the treatment trials in the field of spinal cord injury, emphasizing what has been learned about the effectiveness of the agents and strategies tested and the quality of the methodology. The review aims to provide useful information for the improvement of future trials. The review audience includes practitioners, researchers, and consumers.

METHODS

All publications describing organized trials since the 1960s were analyzed in detail, emphasizing randomized, prospective controlled trials and published Phase I and II trials. Trials were categorized into neuroprotection, surgery, regeneration, and rehabilitation trials. Special attention was paid to design, outcome measures, and case selection.

RESULTS

There are 10 randomized prospective control trials in the acute phase that have provided much useful information. Current neurological grading systems are greatly improved, but still have significant shortcomings, and independent, trained, and blinded examiners are mandatory. Other trial designs should be considered, especially those using adaptive randomization. Only methylprednisolone and thyrotropin-releasing hormone have been shown to be effective, but the results of the former are controversial, and studies involving the latter involved too few patients. None of the surgical trials has proven effectiveness. Currently, a multitude of cell-based Phase I trials in several countries are attracting large numbers of patients, but such treatments are unproven in effectiveness and may cause harm. Only a small number are being conducted in a randomized or blinded format. Several consortia have committed to a promise to improve the conduct of trials.

CONCLUSION

A large number of trials in the field of spinal cord injury have been conducted, but with few proven gains for patients. This review reveals several shortcomings in trial design and makes several recommendations for improvement.

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

STUDY DESIGN

Prospective experimental.

OBJECTIVES

The aim of this study was to develop a quantitative sensory test (QST) that could be used for assessing the level and the density (degree of impairment) of spinal cord injury (SCI) and for monitoring neurological changes in patients with SCI.

SETTING

National Spinal Injuries Centre, Stoke Mandeville Hospital, Buckinghamshire Hospitals NHS Trust, UK.

METHODS

Perceptual threshold to 3 Hz cutaneous electrical stimulation was measured in 30 control subjects and in 45 patients with SCI at American Spinal Injuries Association (ASIA) sensory key points for selected dermatomes between C3 and S2 bilaterally. Electrical perceptual threshold (EPT) was recorded as the lowest ascending stimulus intensity out of three tests at which the subject reported sensation. The level of SCI according to EPT results was established for right and left sides as the most caudal spinal segment at which patient's EPT was within the control range (mean +/- 2 standard deviation (SD)). The level of SCI, according to EPT, was then compared with clinical sensory level derived according to ASIA classification.

RESULTS

In the control group, EPT depended on the dermatome tested and was lowest for T1 (1.01 +/- 0.23 mA, mean +/- SD) and highest for L5 (3.32 +/- 1.14 mA). There was strong correlation between corresponding right and left dermatomes and between repeated assessments. In the SCI group, the level of lesion according to EPT and clinical testing was the same in 43 of the 90 tests (48%). In 37 cases (41%), the EPT level was higher than the clinical level, and in 10 cases (11%), it was lower. Below the level of lesion in incomplete SCI and in the zone of partial preservation in complete SCI, the EPT values in most dermatomes were raised compared with the control group.

CONCLUSIONS

EPT is a simple, reproducible QST that can assess both the level and the density of SCI. It seems to add sensitivity and resolution to the standard clinical testing and could be a useful adjunct in longitudinal monitoring of patients with SCI for research purposes during natural recovery and therapeutic interventions.

SPONSORSHIP

International Spinal Research Trust (ISRT), UK, Grant CLI001.

Thermal perception thresholds: assessing the level of human spinal cord injury

STUDY DESIGN

Controlled, cross-sectional, observational.

OBJECTIVES

To investigate whether quantitative sensory testing (QST) is able to reveal subclinical deficits at the neurological level of lesion in subjects with chronic spinal cord injury (SCI).

SETTING

National Spinal Injuries Centre, Stoke Mandeville Hospital and Imperial College London, UK.

METHODS

QST and clinical assessments were carried out on 18 subjects with complete SCI (American Spinal Injury Association (ASIA) grade A) and 10 subjects with incomplete SCI (ASIA grades B, C or D). A total of 10 healthy subjects acted as controls.

RESULTS

At the level of lesion perceptual thresholds to monofilaments, cold pain and heat pain were similar to values in control subjects but cool and warm thresholds were significantly raised. A correlation between cool and warm thresholds was observed at the level of lesion in complete SCI and between heat and cold pain thresholds at the level of lesion in complete SCI, incomplete SCI and in control subjects. In the zone of partial preservation in complete SCI and below the level of lesion in incomplete SCI, thresholds for all modalities were all different compared to controls.

CONCLUSION

QST reveals impaired thermal sensation in dermatomes clinically defined as normal with ASIA standards. Quantitative thermal testing therefore permits a discriminating assessment of preserved sensation and subclinical deficit and has the potential to improve upon the clinical detection of natural recovery or changes in level of injury following interventions designed to repair SCI.

Cardiovascular responses to vibrostimulation for sperm retrieval in men with spinal cord injury

BACKGROUND/OBJECTIVE

Cardiovascular abnormalities and arrhythmias are common in individuals with spinal cord injury (SCI) who are undergoing vibrostimulation for sperm retrieval. The study aimed to examine cardiovascular control in men with SCI undergoing this procedure.

METHODS

Individuals with chronic cervical (n=8; age: 33.1 +/- 1.9 years) and upper thoracic SCI (n=5; age: 35.2 +/- 2.9 years) volunteered for vibrostimulation, with continuous blood pressure (Finometer) and electrocardiographic monitoring. Patients were characterized further by sympathetic skin responses (SSR) to assess descending autonomic spinal pathways and American Spinal Injury Association (ASIA) scores to assess motor and sensory pathways.

RESULTS

All but one subject with cervical SCI were ASIA A or B and were negative for SSR in the hands and feet. All subjects with upper thoracic SCI were ASIA A or B and were positive for SSR in the hands. Systolic blood pressure was lower in men with cervical injury at rest. Vibrostimulation induced an increase in systolic blood pressure >20 mmHg in all patients with cervical SCI (range = 125/65 - 280/152; median = 167/143 mmHg) and in 2 thoracic subjects (151/104 and 170/121 mmHg). During ejaculation, 6 cervical and 3 thoracic subjects developed arrhythmias (5 with bradycardia, 6 with premature atrial contractions, 4 with ventricular excitation, 1 with junctional rhythm, and 1 with heart block).

CONCLUSION

The vibrostimulation procedure induced electrocardiographic abnormalities and autonomic dysreflexia in subjects with either cervical or high thoracic SCI.

Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

Motor and sensory deficits are well-known consequences of spinal cord injury (SCI). During the last decade, a significant number of experimental and clinical studies have focused on the investigation of autonomic dysfunction and cardiovascular control following SCI. Numerous clinical reports have suggested that unstable blood pressure control in individuals with SCI could be responsible for their increased cardiovascular mortality. The aim of this review is to outline the incidence and pathophysiological mechanisms underlying the orthostatic hypotension that commonly occurs following SCI. We describe the clinical abnormalities of blood pressure control following SCI, with particular emphasis upon orthostatic hypotension. Possible mechanisms underlying orthostatic hypotension in SCI, such as changes in sympathetic activity, altered baroreflex function, the lack of skeletal muscle pumping activity, cardiovascular deconditioning and altered salt and water balance will be discussed. Possible alterations in cerebral autoregulation following SCI, and the impact of these changes upon cerebral perfusion are also examined. Finally, the management of orthostatic hypotension will be considered.

Malignant autonomic dysreflexia in spinal cord injured men

STUDY DESIGN

Case reports.

OBJECTIVES

To present a series of cases of protracted and severe autonomic dysreflexia (AD) in men with spinal cord injury (SCI), who sustained damage to their descending autonomic pathways.

SETTINGS

GF Strong Rehabilitation Centre, Sexual Health Rehabilitation Service, Vancouver Sperm Retrieval Clinic, Vancouver Coastal Health Authority, Vancouver, BC, Canada.

CASE REPORT

AD is a serious complication of SCI triggered by a variety of noxious or non-noxious stimuli below the level of injury. However, we are presenting three cases of protracted, severe AD we have termed 'malignant', owing to the tendency of progressive worsening not usually seen with AD once the alleviating factor is removed. In all three individuals, AD was initially triggered by ejaculation and continued for a period of more than 1 week. Systolic blood pressure in these individuals increased above 220 mmHg and required either acute hospitalization or hospital assessment. Two of the individuals with malignant AD had American Spinal Injury Association (ASIA) B and C high cervical injury, respectively, with the third having a high thoracic ASIA A injury. In addition to detailed history and neurological examination, electrophysiological assessment of sympathetic skin responses (SSR) demonstrated a significant disruption of the descending autonomic pathways in these individuals.

CONCLUSIONS

Our findings suggest that in addition to the severe injury of the motor and sensory pathways (assessed by ASIA score), these individuals sustained severe injury to the supraspinal autonomic control. A combination of strong triggers such as ejaculation and bladder or colono-rectal irritation with total loss of descending autonomic control to the spinal sympathetic circuits could therefore contribute to the unusual manifestation of AD.

Bedside assessment of sympathetic skin response after spinal cord injury: a brief report comparing inspiratory gasp and visual stimulus

STUDY DESIGN

A case control study in five controls, and 20 tetraplegic and paraplegic patients, complete and incomplete.

OBJECTIVE

The aim was to assess the feasibility of a simple test for sympathetic system preservation after spinal cord damage in a pain-free manner and which could be undertaken worldwide without specialist equipment or manpower.

SETTINGS

Patients were attending the Southport Regional Spinal Injuries Centre, England, either as outpatients or as in-patients during rehabilitation.

METHODS

The sympathetic skin response (SSR) was recorded on a single-channel ECG recorder from the right hand and right foot in turn after inspiratory gasp (IG) or visual stimulation.

RESULTS

Unlike the visually evoked SSR, the gasp-evoked SSR was reliable, albeit of variable amplitude, and there was little difference between the hand and foot. Paraplegics had similar SSRs in the hands as the controls. There was minor insignificant habituation of response for the gasp reflex. There was occasional unexpected SSR distally in patients with complete lesions, and in patients with incomplete lesions the responses could not have been predicted from the sensory motor pattern.

CONCLUSIONS

Trained IG induces an SSR which is sufficient to elucidate sympathetic loss following spinal cord injury. It is superior to visual stimulation in this respect. Habituation is not a problem with at least 1 min between tests, and high doses of anticholinergics agents may impair the response.

Motor neurone excitability in back muscles assessed using mechanically evoked reflexes in spinal cord injured patients

OBJECTIVE

The clinical and functional assessment of back muscles in human spinal cord injury (SCI) has received little attention. The aim of this study was to develop a method to assess the level of a thoracic spinal cord lesion based on the reflex activation of back muscles.

METHODS

In 11 control subjects and in 12 subjects with clinically complete thoracic SCI (T2-T12), either a spinous process or an erector spinae muscle was prodded to elicit short latency reflexes recorded electromyographically at the spinal level of stimulation. An electromagnetic servo, attached to a blunt probe, applied stimuli at a frequency of 1 Hz and amplitude of 3 mm. Two trials of 50 mechanical prods were conducted at each site.

RESULTS

Reflexes were evoked in control subjects in 82% of trials when the spinous process was prodded, and in 80% of trials when the muscle was prodded. In contrast, reflexes in SCI subjects could be elicited in 90-100% of trials two segments either above or below the lesion. Reflex responses in control subjects had a mean (SEM) latency of 5.72 (0.53) ms when the spinous process was prodded, and 5.42 (0.42) ms when the muscle was prodded. In the SCI subjects, responses had slightly (but insignificantly) longer latencies both above and below the lesion to either stimulus. The amplitude of reflex responses, expressed as a percentage of the background EMG, was on average 2-3 times larger at the three vertebral levels spanning the lesion in SCI subjects than at sites above or below the lesion or at any level in control subjects.

CONCLUSION

We propose that the size of these mechanically evoked reflexes may be useful in determining the level of thoracic SCI. Furthermore, the reflexes might provide a valuable tool with which to monitor recovery after an intervention to repair or improve function of a damaged spinal cord.

An Appraisal of Ongoing Experimental Procedures in Human Spinal Cord Injury

Clinicians and scientists in the field of spinal cord injury research and medicine are poised to begin translating promising new experimental findings into treatments for people. Advances in experimental regeneration research have led to several transplantation strategies that promote axonal regrowth and partial functional recovery in animal models of injury. In this review, we summarize current knowledge regarding various invasive experimental treatments that have been or are now being applied clinically. Various questions about the timeliness, safety, and benefits of the procedures are under discussion within the spinal cord injury (SCI) research community. We also describe guidelines for carrying out optimal clinical trials and efforts to establish specific international guidelines to translate preclinical treatment strategies into clinical trials in SCI. The clinical trial process and the role that clinical professionals have in advising individuals regarding participation in experimental procedures also is discussed.

International Campaign for Cures of Spinal Cord Injury Paralysis (ICCP): another step forward for spinal cord injury research

For over 20 years, charitable organizations have worked to promote research that will cure the paralysis associated with spinal cord injury (SCI). When they began this quest, the consequences of SCI were thought to be permanent; that once damaged, the spinal cord could not be repaired. Today, the same organizations are credited with funding research that has realized many significant advances, brought new optimism and changed the outlook of researchers, clinicians and injured individuals alike. Progress in understanding the basic biology of spinal cord repair means that it is now a case of how soon useful treatments will be available, rather than if there will ever be anything to offer. With this in mind, many of the organizations that promote spinal cord research have formed an alliance to determine the ways in which their collaboration can hasten progress. The mission and objectives of this alliance, termed the International Campaign for Cures of Spinal Cord Injury Paralysis (ICCP), are described here.