Distinct patterns of spasticity and corticospinal connectivity following complete spinal cord injury

Spasticity Predicts Motor Recovery for Patients with Subacute Motor Complete Spinal Cord Injury

OBJECTIVE

A motor complete spinal cord injury (SCI) results in the loss of voluntary motor control below the point of injury. Some of these patients can regain partial motor function through inpatient rehabilitation; however, there is currently no biomarker to easily identify which patients have this potential. Evidence indicates that spasticity could be that marker. Patients with motor complete SCI who exhibit spasticity show preservation of descending motor pathways, the pathways necessary for motor signals to be carried from the brain to the target muscle. We hypothesized that the presence of spasticity predicts motor recovery after subacute motor complete SCI.

METHODS

Spasticity (Modified Ashworth Scale and pendulum test) and descending connectivity (motor evoked potentials) were tested in the rectus femoris muscle in patients with subacute motor complete (n = 36) and motor incomplete (n = 30) SCI. Motor recovery was assessed by using the International Standards for Neurological Classification of Spinal Cord Injury and the American Spinal Injury Association Impairment Scale (AIS). All measurements were taken at admission and discharge from inpatient rehabilitation.

RESULTS

We found that motor complete SCI patients with spasticity improved in motor scores and showed AIS conversion to either motor or sensory incomplete. Conversely, patients without spasticity showed no changes in motor scores and AIS conversion. In incomplete SCI patients, motor scores improved and AIS conversion occurred regardless of spasticity.

INTERPRETATION

These findings suggest that spasticity represents an easy-to-use clinical outcome that might help to predict motor recovery after severe SCI. This knowledge can improve inpatient rehabilitation effectiveness for motor complete SCI patients. ANN NEUROL 2023.

Segmental motor recovery after cervical spinal cord injury relates to density and integrity of corticospinal tract projections

Cervical spinal cord injury (SCI) causes extensive impairments for individuals which may include dextrous hand function. Although prior work has focused on the recovery at the person-level, the factors determining the recovery of individual muscles are poorly understood. Here, we investigate the muscle-specific recovery after cervical spinal cord injury in a retrospective analysis of 748 individuals from the European Multicenter Study about Spinal Cord Injury (NCT01571531). We show associations between corticospinal tract (CST) sparing and upper extremity recovery in SCI, which improves the prediction of hand muscle strength recovery. Our findings suggest that assessment strategies for muscle-specific motor recovery in acute spinal cord injury are improved by accounting for CST sparing, and complement person-level predictions.

Noxious radiant heat evokes bi-component nociceptive withdrawal reflexes in spinal cord injured humans-A clinical tool to study neuroplastic changes of spinal neural circuits

Investigating nocifensive withdrawal reflexes as potential surrogate marker for the spinal excitation level may widen the understanding of maladaptive nociceptive processing after spinal cord injury (SCI). The aim of this prospective, explorative cross-sectional observational study was to investigate the response behavior of individuals with SCI to noxious radiant heat (laser) stimuli and to assess its relation to spasticity and neuropathic pain, two clinical consequences of spinal hyperexcitability/spinal disinhibition. Laser stimuli were applied at the sole and dorsum of the foot and below the fibula head. Corresponding reflexes were electromyography (EMG) recorded ipsilateral. Motor responses to laser stimuli were analyzed and related to clinical readouts (severity of injury/spasticity/pain), using established clinical assessment tools. Twenty-seven participants, 15 with SCI (age 18-63; 6.5 years post-injury; AIS-A through D) and 12 non-disabled controls, [non-disabled controls (NDC); age 19-63] were included. The percentage of individuals with SCI responding to stimuli (70-77%; p < 0.001), their response rates (16-21%; p < 0.05) and their reflex magnitude (p < 0.05) were significantly higher compared to NDC. SCI-related reflexes clustered in two time-windows, indicating involvement of both A-delta- and C-fibers. Spasticity was associated with facilitated reflexes in SCI (Kendall-tau-b p ≤ 0.05) and inversely associated with the occurrence/severity of neuropathic pain (Fisher's exact p < 0.05; Eta-coefficient p < 0.05). However, neuropathic pain was not related to reflex behavior. Altogether, we found a bi-component motor hyperresponsiveness of SCI to noxious heat, which correlated with spasticity, but not neuropathic pain. Laser-evoked withdrawal reflexes may become a suitable outcome parameter to explore maladaptive spinal circuitries in SCI and to assess the effect of targeted treatment strategies. Registration: https://drks.de/search/de/trial/DRKS00006779.

Spasticity following brain and spinal cord injury: assessment and treatment

PURPOSE OF REVIEW

Spasticity is a common sequela of brain and spinal cord injury and contributes to disability, reduces quality of life, and increases economic burden. Spasticity is still incompletely recognized and undertreated. We will provide an overview of recent published data on the definition, assessment, and prediction, therapeutic advances, with a focus on promising new approaches, and telemedicine applications for spasticity.

RECENT FINDINGS

Two new definitions of spasticity have been recently proposed, but operational criteria should be developed, and test-retest and inter-rater reliability should be explored. Cannabinoids proved to be effective in spasticity in multiple sclerosis, but evidence in other types of spasticity is lacking. Botulinum neurotoxin injection is the first-line therapy for focal spasticity, and recent literature focused on optimizing its efficacy. Several pharmacological, interventional, and nonpharmacological therapeutic approaches for spasticity have been explored but low-quality evidence impedes solid conclusions on their efficacy. The recent COVID-19 pandemic yielded guidelines/recommendations for the use of telemedicine in spasticity.

SUMMARY

Despite the frequency of spasticity, robust diagnostic criteria and reliable assessment scales are required. High-quality studies are needed to support the efficacy of current treatments for spasticity. Future studies should explore telemedicine tools for spasticity assessment and treatment.

Clemastine in remyelination and protection of neurons and skeletal muscle after spinal cord injury

Spinal cord injuries affect nearly five to ten individuals per million every year. Spinal cord injury causes damage to the nerves, muscles, and the tissue surrounding the spinal cord. Depending on the severity, spinal injuries are linked to degeneration of axons and myelin, resulting in neuronal impairment and skeletal muscle weakness and atrophy. The protection of neurons and promotion of myelin regeneration during spinal cord injury is important for recovery of function following spinal cord injury. Current treatments have little to no effect on spinal cord injury and neurogenic muscle loss. Clemastine, an Food and Drug Administration-approved antihistamine drug, reduces inflammation, protects cells, promotes remyelination, and preserves myelin integrity. Recent clinical evidence suggests that clemastine can decrease the loss of axons after spinal cord injury, stimulating the differentiation of oligodendrocyte progenitor cells into mature oligodendrocytes that are capable of myelination. While clemastine can aid not only in the remyelination and preservation of myelin sheath integrity, it also protects neurons. However, its role in neurogenic muscle loss remains unclear. This review discusses the pathophysiology of spinal cord injury, and the role of clemastine in the protection of neurons, myelin, and axons as well as attenuation of skeletal muscle loss following spinal cord injury.

Utility of transcranial magnetic stimulation in the assessment of spinal cord injury: Current status and future directions

Comprehensive assessment following traumatic spinal cord injury (SCI) is needed to improve prognostication, advance the understanding of the neurophysiology and better targeting of clinical interventions. The International Standards for Neurological Classification of Spinal Cord Injury is the most common clinical examination recommended for use after a SCI. In addition, there are over 30 clinical assessment tools spanning across different domains of the International Classification of Functioning, Disability, and Health that have been validated and recommended for use in SCI. Most of these tools are subjective in nature, have limited value in predicting neurologic recovery, and do not provide insights into neurophysiological mechanisms. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiology technique that can supplement the clinical assessment in the domain of body structure and function during acute and chronic stages of SCI. TMS offers a better insight into neurophysiology and help in better detection of residual corticomotor connectivity following SCI compared to clinical assessment alone. TMS-based motor evoked potential and silent period duration allow study of excitatory and inhibitory mechanisms following SCI. Changes in muscle representations in form of displacement of TMS-based motor map center of gravity or changes in the map area can capture neuroplastic changes resulting from SCI or following rehabilitation. Paired-pulse TMS measures help understand the compensatory reorganization of the cortical circuits following SCI. In combination with peripheral stimulation, TMS can be used to study central motor conduction time and modulation of spinal reflexes, which can be used for advanced diagnostic and treatment purposes. To strengthen the utility of TMS in SCI assessment, future studies will need to standardize the assessment protocols, address population-specific concerns, and establish the psychometric properties of TMS-based measurements in the SCI population.

Prevalence of spasticity in humans with spinal cord injury with different injury severity

Spasticity is one of the most common symptoms manifested following spinal cord injury (SCI). The aim of this study was to assess spasticity in individuals with subacute and chronic SCI with different injury severity, standardizing the time and assessments of spasticity. We tested 110 individuals with SCI classified by the American Spinal Injury Association Impairment Scale (AIS) as either motor complete (AIS A and B; subacute, n = 25; chronic, n = 33) or motor incomplete (AIS C and D; subacute, n = 23; chronic, n = 29) at a similar time after injury (subacute, ∼1 mo after injury during inpatient rehabilitation and chronic, ≥1 yr after injury) using clinical (modified Ashworth scale) and kinematic (pendulum test) outcomes to assess spasticity in the quadriceps femoris muscle. Using both methodologies, we found that among individuals with subacute motor complete injuries, only a minority showed spasticity, whereas the majority exhibited no spasticity. This finding stands in contrast to individuals with subacute motor incomplete injury, where both methodologies revealed that a majority exhibited spasticity, whereas a minority exhibited no spasticity. In chronic injuries, most individuals showed spasticity regardless of injury severity. Notably, when spasticity was present, its magnitude was similar across injury severity in both subacute and chronic injuries. Our results suggest that the prevalence, not the magnitude, of spasticity differs between individuals with motor complete and incomplete SCI in the subacute and chronic stages of the injury. We thus argue that considering the "presence of spasticity" might help the stratification of participants with motor complete injuries for clinical trials.NEW & NOTEWORTHY The prevalence of spasticity in humans with SCI remains poorly understood. Using kinematic and clinical outcomes, we examined spasticity in individuals with subacute and chronic injuries of different severity. We found that spasticity in the quadriceps femoris muscle was more prevalent among individuals with subacute motor incomplete than in those with motor complete injuries. However, in a different group of individuals with chronic injuries, no differences were found in the prevalence of spasticity across injury severity.

Surface EMG in Subacute and Chronic Care after Traumatic Spinal Cord Injuries

Background: Traumatic spinal cord injury (SCI) is a devastating condition commonly originating from motor vehicle accidents or falls. Trauma care after SCI is challenging; after decompression surgery and spine stabilization, the first step is to assess the location and severity of the traumatic lesion. For this, clinical outcome measures are used to quantify the residual sensation and volitional control of muscles below the level of injury. These clinical assessments are important for decision-making, including the prediction of the recovery potential of individuals after the SCI. In clinical care, this quantification is usually performed using sensation and motor scores, a semi-quantitative measurement, alongside the binary classification of the sacral sparing (yes/no). Objective: In this perspective article, I review the use of surface EMG (sEMG) as a quantitative outcome measurement in subacute and chronic trauma care after SCI. Methods: Here, I revisit the main findings of two comprehensive scoping reviews recently published by our team on this topic. I offer a perspective on the combined findings of these scoping reviews, which integrate the changes in sEMG with SCI and the use of sEMG in neurorehabilitation after SCI. Results: sEMG provides a complimentary assessment to quantify the residual control of muscles with great sensitivity and detail compared to the traditional clinical assessments. Our scoping reviews unveiled the ability of the sEMG assessment to detect discomplete lesions (muscles with absent motor scores but present sEMG). Moreover, sEMG is able to measure the spontaneous activity of motor units at rest, and during passive maneuvers, the evoked responses with sensory or motor stimulation, and the integrity of the spinal cord and descending tracts with motor evoked potentials. This greatly complements the diagnostics of the SCI in the subacute phase of trauma care and deepens our understanding of neurorehabilitation strategies during the chronic phase of the traumatic injury. Conclusions: sEMG offers important insights into the neurophysiological factors underlying sensorimotor impairment and recovery after SCIs. Although several qualitative or semi-quantitative outcome measures determine the level of injury and the natural recovery after SCIs, using quantitative measures such as sEMG is promising. Nonetheless, there are still several barriers limiting the use of sEMG in the clinical environment and a need to advance high-density sEMG technology.

Spasticity Management after Spinal Cord Injury: The Here and Now

Spasticity is a common comorbidity of spinal cord injury (SCI) that is characterized by velocity dependent tone and spasms manifested by uninhibited reflex activity of muscles below the level of injury. For some, spasticity can be beneficial and facilitate functional standing, transfers, and some activities of daily living. For others, it may be problematic, painful, and interfere with mobility and function. This manuscript will address the anatomy and physiology of neuromuscular reflexes as well as the pathophysiology that occurs after SCI. Spasticity assessment will be discussed in terms of clinical history and findings on physical examinations, including responses to passive and active movement, deep tendon reflexes, and other long tract signs of upper motor neuron injury, as well as gait and function. Management strategies will be discussed including stretch, modalities, pharmacotherapy, neurolysis, and surgical options.