Tendon reflexes for predicting movement recovery after acute spinal cord injury in humans

Predicting motor function recovery in cervical spinal cord injury-induced complete paralysis with reflex response

STUDY DESIGN

A retrospective clinical study.

OBJECTIVE

To elucidate the usefulness of the patellar tendon reflex (PTR), bulbocavernosus reflex (BCR), and plantar response (PR) as factors in the prognostic prediction of motor function in complete paralysis due to cervical spinal cord injuries (CSCIs) at the acute phase.

SETTING

Department of Orthopedic Surgery, Spinal Injuries Center, Japan.

METHODS

99 patients assessed as the American Spinal Injury Association Impairment Scale (AIS) grade A (AIS A) were included in this study. The PTR, BCR, and PR were evaluated respectively as positive or negative at the time of injury. We classified the patients into two groups based on their neurological recovery at 3 months after injury: "recovered" group was defined as AIS C, D, or E; "non-recovered" group was defined as AIS A or B.

RESULTS

Eight patients demonstrated positive PTR, while 91 demonstrated negative. Three out of eight patients with positive PTR (37.5%) were R group, while 83 out of 91 patients with negative PTR (91.2%) were N group. A significant difference was observed (p = 0.043). For BCR, no significant difference was observed (p > 0.05). Twenty-six patients demonstrated positive PTR, while 73 demonstrated negative. Nine out of twenty-six patients with positive PR (34.6%) were R group, while 71 out of 73 patients with negative PR (97.3%) were N group. A significant difference was observed (p = 0.000068).

CONCLUSION

The PTR and PR are useful for poor prognostic prediction of motor function in CSCI at the acute phase.

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.

Revisit Spinal Shock: Pattern of Reflex Evolution during Spinal Shock

When the spinal cord is suddenly severed, all the fundamental functions of the spinal cord below the level of injury including the spinal cord reflexes are immediately depressed, which is referred to as spinal shock. The resolution of spinal shock occurs over a period of days to months, and spinal shock slowly transitions to spasticity. The definition of spinal shock and the pattern of reflex recovery or evolution remains as an issue of debate and controversy. The identification of clinical signs that determine the duration of spinal shock is controversial. The underlying mechanisms of spinal shock are also not clearly defined. Various authors have defined the termination of spinal shock as the appearance of the bulbocavernosus reflex, the recovery of deep tendon reflexes, or the return of reflexic detrusor activity. However, many questions remain to be answered, such as: When should we define spinal shock as the end? What types of reflexes appear first among polysynaptic cutaneous reflexes, monosynaptic deep tendon reflexes, and pathological reflexes? Should it include changes in autonomic reflexes such as a detrusor reflex?

Common neural structures activated by epidural and transcutaneous lumbar spinal cord stimulation: Elicitation of posterior root-muscle reflexes

Epidural electrical stimulation of the lumbar spinal cord is currently regaining momentum as a neuromodulation intervention in spinal cord injury (SCI) to modify dysregulated sensorimotor functions and augment residual motor capacity. There is ample evidence that it engages spinal circuits through the electrical stimulation of large-to-medium diameter afferent fibers within lumbar and upper sacral posterior roots. Recent pilot studies suggested that the surface electrode-based method of transcutaneous spinal cord stimulation (SCS) may produce similar neuromodulatory effects as caused by epidural SCS. Neurophysiological and computer modeling studies proposed that this noninvasive technique stimulates posterior-root fibers as well, likely activating similar input structures to the spinal cord as epidural stimulation. Here, we add a yet missing piece of evidence substantiating this assumption. We conducted in-depth analyses and direct comparisons of the electromyographic (EMG) characteristics of short-latency responses in multiple leg muscles to both stimulation techniques derived from ten individuals with SCI each. Post-activation depression of responses evoked by paired pulses applied either epidurally or transcutaneously confirmed the reflex nature of the responses. The muscle responses to both techniques had the same latencies, EMG peak-to-peak amplitudes, and waveforms, except for smaller responses with shorter onset latencies in the triceps surae muscle group and shorter offsets of the responses in the biceps femoris muscle during epidural stimulation. Responses obtained in three subjects tested with both methods at different time points had near-identical waveforms per muscle group as well as same onset latencies. The present results strongly corroborate the activation of common neural input structures to the lumbar spinal cord—predominantly primary afferent fibers within multiple posterior roots—by both techniques and add to unraveling the basic mechanisms underlying electrical SCS.

Clinical predictors of neurological outcome, functional status, and survival after traumatic spinal cord injury: a systematic review

OBJECT

The object of this study was to identify, by means of a systematic review of the literature, the acute clinical predictors of neurological outcome, functional outcome, and survival after traumatic spinal cord injury (SCI).

METHODS

A comprehensive computerized literature review search was performed, using MEDLINE, PubMed, EMBASE, CINAHL, and the Cochrane Database of Systematic Reviews. Selected articles were classified according to their level of evidence. Articles were then stratified into one of 3 domains depending on whether the primary focus was clinical prediction of 1) neurological outcome, 2) functional status, or 3) survival. For each study selected, clinical predictors related to patient demographic characteristics, injury mechanism, or neurological examination findings were extracted, and the individual relationship to outcome was defined.

RESULTS

The initial search resulted in 376 citations. After application of the inclusion and exclusion criteria and study review, 51 relevant articles were identified and graded. Of these, 25 provided predictors for neurological outcome, 22 for functional outcome, and 15 for survival, with several of the articles providing information on more than one type of outcome. All of the included studies were designated as providing Class I, II, or III levels of evidence. The severity of neurological injury (as measured by admission Americal Spinal Injury Association Impairment Scale grade, Frankel grade, or injury completeness), level of injury, and the presence of a zone of partial preservation were consistent predictors of neurological outcome. Severity of neurological injury, level of injury, reflex pattern, and age were consistent predictors of functional outcome. Finally, severity of neurological injury, level of injury, age, and the presence of multisystem trauma seen with higher-energy injury mechanisms were consistent predictors of survival.

CONCLUSIONS

On the basis on this review, the authors have identified a constellation of acute clinical features that may help to define an individual's profile for recovery and survival after SCI. This study will help to facilitate communication in the clinical realm and assist in classifying subsets of patients within future clinical studies.

A clinical prediction model for long-term functional outcome after traumatic spinal cord injury based on acute clinical and imaging factors

To improve clinicians' ability to predict outcome after spinal cord injury (SCI) and to help classify patients within clinical trials, we have created a novel prediction model relating acute clinical and imaging information to functional outcome at 1 year. Data were obtained from two large prospective SCI datasets. Functional independence measure (FIM) motor score at 1 year follow-up was the primary outcome, and functional independence (score ≥ 6 for each FIM motor item) was the secondary outcome. A linear regression model was created with the primary outcome modeled relative to clinical and imaging predictors obtained within 3 days of injury. A logistic model was then created using the dichotomized secondary outcome and the same predictor variables. Model validation was performed using a bootstrap resampling procedure. Of 729 patients, 376 met the inclusion criteria. The mean FIM motor score at 1 year was 62.9 (±28.6). Better functional status was predicted by less severe initial American Spinal Injury Association (ASIA) Impairment Scale grade, and by an ASIA motor score >50 at admission. In contrast, older age and magnetic resonance imaging (MRI) signal characteristics consistent with spinal cord edema or hemorrhage predicted worse functional outcome. The linear model predicting FIM motor score demonstrated an R-square of 0.52 in the original dataset, and 0.52 (95% CI 0.52,0.53) across the 200 bootstraps. Functional independence was achieved by 148 patients (39.4%). For the logistic model, the area under the curve was 0.93 in the original dataset, and 0.92 (95% CI 0.92,0.93) across the bootstraps, indicating excellent predictive discrimination. These models will have important clinical impact to guide decision making and to counsel patients and families.

Clinical diagnosis and prognosis following spinal cord injury

Spinal cord injury (SCI) is a sudden, life-altering event. Injury severity and accompanying recovery vary considerably from individual to individual. The most important determinant of prognosis is whether an injury is clinically complete or incomplete. While approximately 10-20% of complete injuries convert to incomplete during the first year post-injury, the magnitude of motor recovery following complete SCI is limited or absent. Robust functional motor recovery (e.g., weight-bearing, ambulation) distal to the zone of injury is rare. Recovery following incomplete SCI is particularly variable, and anywhere from 20% to 75% of individuals will recover some degree of walking capacity by 1 year post-injury. This is related to presenting injury severity (American Spinal Injury Association Impairment Scale grade); however, even 20-50% of individuals who present as motor complete, sensory incomplete will walk in some capacity by 1 year post-injury. Regardless, for both complete and incomplete injuries, the majority of recovery is observed during the initial 9-12 months, with a relative plateau reached by 12-18 months post-injury. Magnetic resonance imaging (MRI) provides valuable adjunct information when a bedside clinical assessment cannot be completed. The presence of intramedullary hemorrhage and extended segments of edema have been associated with clinically complete SCI.

The impact of sacral sensory sparing in motor complete spinal cord injury

OBJECTIVE

To determine the effect of sensory sparing in motor complete persons with spinal cord injury (SCI) on completion of rehabilitation on neurologic, functional, and social outcomes reported at 1 year.

DESIGN

Secondary analysis of longitudinal data collected by using prospective survey-based methods.

SETTING

Data submitted to the National SCI Statistical Center Database.

PARTICIPANTS

Of persons (N=4106) enrolled in the model system with a motor complete injury (American Spinal Injury Association Impairment Scale [AIS] grade A or B) at the time of discharge between 1997 and 2007, a total of 2331 (56.8%) completed a 1-year follow-up interview (Form II) and 1284 (31.3%) had complete data for neurologic (eg, AIS grade, injury level) variables at 1 year.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

AIS grade (A vs B) at 1 year, bladder management, hospitalizations, perceived health status, motor FIM items, Satisfaction With Life Scale, depressive symptoms, and social participation.

RESULTS

Compared with persons with AIS grade A at discharge, persons with AIS grade B were less likely to require indwelling catheterization and be hospitalized and more likely to perceive better health, report greater functional independence (ie, self-care, sphincter control, mobility, locomotion), and report social participation in the first year postinjury. A greater portion of individuals with AIS grade B at discharge had improved neurologic recovery at 1 year postinjury than those with AIS grade A. Significant AIS group differences in 1-year outcomes related to physical health were maintained after excluding persons who improved to motor incomplete status for only bladder management and change in perceived health status. This recognition of differences between persons with motor complete injuries (AIS grade A vs B) has important ramifications for the field of SCI rehabilitation and research.

Patellar tendon reflex as a predictor of improving motor paralysis in complete paralysis due to cervical cord injury

STUDY DESIGN

A retrospective study.

OBJECTIVE

We have encountered several cases of complete sensorimotor paralysis in which patellar tendon reflex (PTR) was demonstrated approximately 3 days after injury and improvement of motor paralysis was subsequently achieved. We considered that PTR apparent in the early stage after injury may offer an index to predict improvements in motor paralysis.

MATERIALS AND METHODS

A total of 142 patients assessed as ASIA Impairment Scale A on admission from 1979 to 1998 were included in the study. The patients who demonstrated PTR within 72 h after injury were classified as the PTR(+) group and those who did not constituted the PTR(-) group. With regard to the method of motor paralysis assessment at about 6 months after injury, patients assessed as ASIA Impairment Scale A or B (that is, complete motor paralysis) were classified as 'Non-recovered', whereas those assessed as ASIA Impairment Scale C, D or E (that is, showing obvious improvement of motor paralysis) were considered as 'Recovered'.

RESULTS

A significant difference was noted between groups, with the Recovered group including 16 of the 17 PTR(+) patients (94.1%) and 11 of the 115 PTR(-) patients (9.6%) (P<0.0001).

CONCLUSION

The results obtained indicate that motor paralysis recovery could be expected at a very high rate among patients demonstrating PTR within 72 h of injury. As all physicians should be familiar with the PTR, this seems to represent a simple and highly useful sign to predict improvements in motor paralysis during the acute stage of cervical cord injury.

Spinal cord injury medicine. 2. Acute care management of traumatic and nontraumatic injury

This self-directed learning module highlights the basic acute care management of traumatic and nontraumatic spinal cord injury (SCI). It is part of the chapter on SCI medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. Acute traumatic SCI is optimally managed in a level 1 trauma center. Decompression of the neural elements, stabilization of the spine, and maintenance of tissue perfusion are fundamental to optimizing outcomes. SCI patients are at high risk of pressure ulcers, venous thromboembolism, stress ulceration, bowel impaction, dysphagia, and pulmonary complications. Physiatric interventions are needed to prevent these complications. Prognostication of neurologic outcome based on early examination is an important skill to aid in creating a rehabilitation plan and to test for efficacy of early interventions. Nontraumatic SCI is an increasing population in rehabilitation centers. Establishing a diagnosis and treatment plan is essential, in conjunction with prevention of complications and early physiatric intervention.

OVERALL ARTICLE OBJECTIVES

(a) To describe the diagnostic evaluation of traumatic and nontraumatic spinal cord injuries and (b) to summarize the medical, surgical, and physiatric interventions during acute hospitalization for these injuries.

Enhanced stretch reflex excitability of the soleus muscle in persons with incomplete rather than complete chronic spinal cord injury

OBJECTIVE

To compare excitabilities of spinal stretch reflex among clinically complete spinal cord injury (SCI), incomplete SCI, elderly healthy, and young healthy subjects.

DESIGN

Case comparison.

SETTING

Research laboratory.

PARTICIPANTS

Volunteer sample of 12 complete SCI, 10 incomplete SCI, 10 elderly, and 11 young subjects.

INTERVENTION

Mechanically induced stretch reflex, H-reflex, and M response in electromyographic activity of the soleus muscle were recorded in all subjects.

MAIN OUTCOME MEASURES

Absolute peak-to-peak stretch reflex amplitude and maximum H-reflex (Hmax), and those values relative to the maximum M response (Mmax) amplitude (relative peak-to-peak stretch reflex amplitude) and H/M ratio.

RESULTS

Both the absolute and relative peak-to-peak stretch reflex amplitudes showed the greatest values in incomplete SCI among the 4 groups. Although absolute and relative peak-to-peak stretch reflex amplitudes of the incomplete SCI group were greater than those of the complete SCI group, the H/M ratios of both groups were comparable, and were greater than those of the younger and elderly groups.

CONCLUSIONS

The results suggest that the greater absolute and relative peak-to-peak stretch reflex amplitudes of incomplete SCI were mostly due to the greater maximum motor potential (Mmax), while the elevated spinal motoneuronal excitability shown by the increased H/M ratio was maintained in the chronic stage after both complete and incomplete SCIs.

Functional plasticity following spinal cord lesions

Spinal cord injury results in marked modification and reorganization of several reflex pathways caudal to the injury. The sudden loss or disruption of descending input engenders substantial changes at the level of primary afferents, interneurons, and motoneurons thus dramatically influencing sensorimotor interactions in the spinal cord. As a general rule reflexes are initially depressed following spinal cord injury due to severe reductions in motoneuron excitability but recover and in some instances become exaggerated. It is thought that modified inhibitory connections and/or altered transmission in some of these reflex pathways after spinal injury as well as the recovery and enhancement of membrane properties in motoneurons underlie several symptoms such as spasticity and may explain some characteristics of spinal locomotion observed in spinally transected animals. Indeed, after partial or complete spinal lesions at the last thoracic vertebra cats recover locomotion when the hindlimbs are placed on a treadmill. Although some deficits in spinal locomotion are related to lesion of specific descending motor pathways, other characteristics can also be explained by changes in the excitability of reflex pathways mentioned above. Consequently it may be the case that to reestablish a stable walking pattern that modified afferent inflow to the spinal cord incurred after injury must be normalized to enable a more normal re-expression of locomotor rhythm generating networks. Indeed, recent evidence demonstrates that step training, which has extensively been shown to facilitate and ameliorate locomotor recovery in spinal animals, directly influences transmission in simple reflex pathways after complete spinal lesions.

Brain motor system function after chronic, complete spinal cord injury

Most therapies under development to restore motor function after spinal cord injury (SCI) assume intact brain motor functions. To examine this assumption, 12 patients with chronic, complete SCI and 12 controls underwent functional MRI during attempted, and during imagined, right foot movement, each at two force levels. In patients with SCI, many features of normal motor system function were preserved, however, several departures from normal were apparent: (i) volume of activation was generally much reduced, e.g. 4-8% of normal in primary sensorimotor cortex, in the setting of twice normal variance in signal change; (ii) abnormal activation patterns were present, e.g. increased pallido-thalamocortical loop activity during attempted movement and abnormal processing in primary sensorimotor cortex during imagined movement; and (iii) modulation of function with change in task or in force level did not conform to patterns seen in controls, e.g. in controls, attempted movement activated more than imagined movement did within left primary sensorimotor cortex and right dorsal cerebellum, while imagined movement activated more than attempted movement did in dorsolateral prefrontal cortex and right precentral gyrus. These modulations were absent in patients with SCI. Many features of brain motor system function during foot movement persist after chronic complete SCI. However, substantial derangements of brain activation, poor modulation of function with change in task demands and emergence of pathological brain events were present in patients. Because brain function is central to voluntary movement, interventions that aim to improve motor function after chronic SCI likely also need to attend to these abnormalities of brain function.

Abductor hallucis for monitoring lower-limb recovery after spinal cord injury in man

STUDY DESIGN

Electromyogram (EMG) study on patients with acute spinal cord injury (SCI).

OBJECTIVES

We hypothesized that subjects with mild to moderate acute SCI would have a higher probability of recovering function in intrinsic muscles of the foot compared to more proximal lower-limb muscles, based on the relative density of corticospinal tract innervation to these different motoneuron pools.

SETTING

Miami and Syracuse, USA.

METHODS

We conducted repeated measures of EMG during voluntary contractions from lower-limb muscles in subjects with acute traumatic SCI. For this study, analysis was restricted to those subjects who had either no recruitment (ie 'motor-complete') or limited recruitment (ie 'motor-incomplete') in any lower-limb muscle of either leg during the initial evaluation, and all of whom had converted to a motor-incomplete status in one or both legs at the time of final evaluation. Recruitment of the abductor hallucis (AbH) muscle during contraction attempts was judged as being either 'present' or 'absent', based upon the presence or absence of EMG-based volitional motor unit recruitment.

RESULTS

A total of 70 subjects were included in this study. Of these, 58 had motor-incomplete injury at or rostral to the T10 vertebral level, and another 12 had injury caudal to T10. In the former group, the AbH muscle showed a recovery probability that was considerably higher than that of other lower-limb muscles. Quite the opposite pattern was seen in persons with injury caudal to T10. In these subjects, recruitment was more common in proximal muscles of the thigh (psoas and quadriceps), and least common in the AbH muscle.

DISCUSSION

For persons with SCI at or rostral to the T10 vertebral level, the AbH muscle proved to be an earlier and more sensitive indicator of lower-limb contraction recovery following acute SCI compared to other lower-limb muscles. Including this intrinsic muscle of the foot as part of a neurologic assessment of muscle function after SCI should increase the test's sensitivity to preserved (or restored) supraspinal motor influence over lower-limb motoneuron pools, and is recommended.