Pathophysiology of spastic paresis. II: Emergence of muscle overactivity

Botulinum Neurotoxin A injections influence stretching of the gastrocnemius muscle-tendon unit in an animal model

Botulinum Neurotoxin A (BoNT-A) injections have been used for the treatment of muscle contractures and spasticity. This study assessed the influence of (BoNT-A) injections on passive biomechanical properties of the muscle-tendon unit. Mousegastrocnemius muscle (GC) was injected with BoNT-A (n = 18) or normal saline (n = 18) and passive, non-destructive, in vivo load relaxation experimentation was performed to examine how the muscle-tendon unit behaves after chemical denervation with BoNT-A. Injection of BoNT-A impaired passive muscle recovery (15% vs. 35% recovery to pre-stretching baseline, p < 0.05) and decreased GC stiffness (0.531 ± 0.061 N/mm vs. 0.780 ± 0.037 N/mm, p < 0.05) compared to saline controls. The successful use of BoNT-A injections as an adjunct to physical therapy may be in part attributed to the disruption of the stretch reflex; thereby modulating in vivo passive muscle properties. However, it is also possible that BoNT-A injection may alter the structure of skeletal muscle; thus modulating the in vivo passive biomechanical properties of the muscle-tendon unit.

Unraveling the interaction between pathological upper limb synergies and compensatory trunk movements during reach-to-grasp after stroke: a cross-sectional study

The aim of the present study was to identify how pathological limb synergies between shoulder and elbow movements interact with compensatory trunk movements during a functional movement with the paretic upper limb after stroke. 3D kinematic joint and trunk angles were measured during a reach-to-grasp movement in 46 patients with stroke and 12 healthy individuals. We used principal component analyses (PCA) to identify components representing linear relations between the degrees of freedom of the upper limb and trunk across patients with stroke and healthy participants. Using multivariate logistic regression analysis, we investigated whether component scores were related to the presence or absence of basic limb synergies as indicated by the arm section of the Fugl-Meyer motor assessment (FMA). Four and three principal components were extracted in patients with stroke and healthy individuals, respectively. Visual inspection revealed that the contribution of joint and trunk angles to each component differed substantially between groups. The presence of the flexion synergy (Shoulder Abduction and Elbow Flexion) was reflected by component 1, whereas the compensatory role of trunk movements for lack of shoulder and elbow movements was reflected by components 2 and 3 respectively. The presence or absence of basic limb synergies as determined by means of the FMA was significantly related to components 2 (p = 0.014) and 3 (p = 0.003) in patients with stroke. These significant relations indicate that PCA is a useful tool to identify clinically meaningful interactions between compensatory trunk movements and pathological synergies in the elbow and shoulder during reach-to-grasp after stroke.

[Pathophysiology of spasticity]

The term "spasticity" describes the velocity-dependent increase in tonic stretch reflexes. The symptom is commonly seen in patients with injury to the central nervous system. It is rarely isolated but, instead, part of a set of symptoms that is sometimes confusing. However, the pathophysiology of the symptom has evolved over the past three decades, and it is now considered part of a global process that includes not only spinal reflex loop modifications, but also changes in the biomechanical properties of muscle fibers. Finally, recent studies of changes in the membrane properties of motor neurons and the occurrence of plateau potential have opened new perspectives. This review aims to describe these new pathophysiological models.

Positive effects of robotic exoskeleton training of upper limb reaching movements after stroke

This study, conducted in a group of nine chronic patients with right-side hemiparesis after stroke, investigated the effects of a robotic-assisted rehabilitation training with an upper limb robotic exoskeleton for the restoration of motor function in spatial reaching movements. The robotic assisted rehabilitation training was administered for a period of 6 weeks including reaching and spatial antigravity movements. To assess the carry-over of the observed improvements in movement during training into improved function, a kinesiologic assessment of the effects of the training was performed by means of motion and dynamic electromyographic analysis of reaching movements performed before and after training. The same kinesiologic measurements were performed in a healthy control group of seven volunteers, to determine a benchmark for the experimental observations in the patients' group. Moreover degree of functional impairment at the enrolment and discharge was measured by clinical evaluation with upper limb Fugl-Meyer Assessment scale (FMA, 0-66 points), Modified Ashworth scale (MA, 0-60 pts) and active ranges of motion. The robot aided training induced, independently by time of stroke, statistical significant improvements of kinesiologic (movement time, smoothness of motion) and clinical (4.6 ± 4.2 increase in FMA, 3.2 ± 2.1 decrease in MA) parameters, as a result of the increased active ranges of motion and improved co-contraction index for shoulder extension/flexion. Kinesiologic parameters correlated significantly with clinical assessment values, and their changes after the training were affected by the direction of motion (inward vs. outward movement) and position of target to be reached (ipsilateral, central and contralateral peripersonal space). These changes can be explained as a result of the motor recovery induced by the robotic training, in terms of regained ability to execute single joint movements and of improved interjoint coordination of elbow and shoulder joints.

A prospective, multicentre, randomized, double-blind, placebo-controlled trial of onabotulinumtoxinA to treat plantarflexor/invertor overactivity after stroke

OBJECTIVE

To examine the safety and efficacy of onabotulinumtoxinA (Botox) for plantarflexor overactivity following stroke.

DESIGN

Double-blind randomized controlled trial, open-label extension phase.

SETTING

Neurology rehabilitation facilities.

SUBJECTS

Eighty-five subjects with lower limb hypertonia received 200 U (n = 28) or 300 U (n = 28) of onabotulinumtoxinA or saline (n = 29) injection.

PRIMARY MEASURES

Plantarflexor Ashworth scores at 12 weeks post injection and adverse events. Secondary measures: self-reported spasm frequency and pain, physician rating of hypertonia severity, gait quality and active dorsiflexion.

RESULTS

Differences were not seen between onabotulinumtoxinA groups; hence data were pooled. Incidence of adverse events was not different between groups (P = 0.61). Reduction in hypertonia was not different between groups at 12 weeks (P = 0.53); however for subjects with Ashworth scores of >3 at baseline, 14/31 in the onabotulinumtoxinA group demonstrated a reduction of >1 grade versus 1/17 receiving placebo injection (P = 0.01). Overall, onabotulinumtoxinA-injected subjects demonstrated significantly greater improvement in spasm frequency (22/54 versus 4/29, P = 0.01), pain reduction (8/54 versus 1/29, P = 0.02), active dorsiflexion (8/54 versus 1/29 P = 0.03) and gait quality (17/54 versus 6/29, P = 0.02) than controls. In the open-label phase, a second onabotulinumtoxinA injection was associated with greater hypertonia reduction (P = 0.005) and gait quality (P = 0.002) compared with single injection.

CONCLUSIONS

OnabotulinumtoxinA injection for ankle flexor overactivity after stroke was safe and well tolerated but did not alter local spasticity at 12 weeks; it did reduce spasms and improve gait quality. There were no detectable differences between higher and lower doses. A second injection may be associated with greater change.

[Fundamental theory and practice in stroke rehabilitation from acute stage to chronic stage]

One of the most important objects of stroke rehabilitation is motor recovery from acute stage to chronic stage. Reorganization theory of motor circuits in the cerebral cortex contributing to recovery following stroke is proposed. In acute stage motor recovery depends on residual corticospinal tract excitability from onset to 3 months (1(st) stage recovery) . In next stage alternative output system is used according to intracortical excitability depending on intracortical disinhibition at the peak of 3 months (2(nd) stage recovery) . At 6 months and beyond training-induced synaptic strengthening becomes better established, and new networks are better reorganized (3(rd)stage recovery) . Stroke rehabilitation programs from acute stage are required depending on this stage theory. With each stage to select and perform the most effective rehabilitation programs are necessary. Two obstruction factors of motor recovery are indicated. One of them is Wallerian degeneration of corticospinal tract. Early Wallerian degeneration of the corticospinal tract that is seen on diffusion weighted MRI was reported. The appearance of Wallerian degeneration at acute stage should be directed to more attention as motor recovery inhibition. Next obstruction factor is development of spasticity from acute stage. Spastic paresis is subjected over time to immobilization of the paretic body part and chronic disuse of the paretic body part, which are avoidable through early rehabilitation intervention. Recently various interventions were proposed for motor recovery. The combination of repetitive transcranial magnetic stimulation and intensive occupational therapy by Abo (2010) are recommended to recovery hand function at chronic stage as 3(rd) stage recovery.

Assessing the neurophysiological effects of botulinum toxin treatment for adults with focal limb spasticity: a systematic review

To examine effectiveness of botulinum toxin therapy (BoNT), accurate quantification of the neurological component of underlying spasticity is needed.

PURPOSE

Systematically identify and summarize literature on neurophysiological methods to test the effectiveness of BoNT, discuss methodological aspects, and recommend best techniques for clinical and research settings.

METHODS

Electronic databases were searched using specific keywords. Reviews and reference lists were hand-checked to find relevant studies. Studies in adults with focal limb spasticity were included.

RESULTS

Over 300 articles were scanned for relevance, and a list of 90 relevant articles was made. After excluding reviews and studies in healthy controls or non-spasticity related BoNT, 22 articles were reviewed. Neurophysiological techniques included electromyography (EMG; n = 11), electrical nerve stimulation (n = 13), transcranial magnetic stimulation (TMS; n = 1), functional magnetic resonance imaging (fMRI; n = 1), reflex threshold (n = 4), Achilles tendon reflex (n = 1), reflex latency (n = 1).

DISCUSSION

Maximum M-wave amplitude (M-max) and stretch reflex threshold techniques were successfully used to measure the neurophysiological effects of BoNT and have high test-retest reliability. EMG techniques require effective magnitude normalization techniques and establishing test-retest reliability.

CONCLUSION

Serial electrical nerve stimulation can be incorporated into clinical practice to assist in follow-up. We recommend using M-max and stretch reflex threshold techniques to assess the neurophysiological effects.

A literature review of the pathophysiology and onset of post-stroke spasticity

BACKGROUND

Spasticity occurs after stroke and gives rise to substantial burden for patients and caregivers. Although it has been studied for many years, its definition continues to undergo reconsideration and revision. This partly reflects the diversity of its manifestations and that its pathophysiology, although well studied, is still debated.

METHODS

A literature review was carried out to define the pathophysiology and risk factors for onset of post-stroke spasticity.

RESULTS

It is clear that an acquired brain injury, including stroke, results in an imbalance of inhibitory and excitatory impulses that leads to upper motor neuron symptoms and that the location and extent of the lesions result in differing symptoms and degrees of spastic severity. The onset of spasticity is highly variable and may occur shortly or more than 1 year after stroke. The current understanding of spasticity onset is complicated by the role of contractures, which have been assumed to arise out of spasticity but may have a role in its cause. Other possibly predictive factors for the risk of post-stroke spasticity have been identified, including early arm and leg weakness, left-sided weakness, early reduction in activities of daily living, and a history of smoking.

CONCLUSIONS

Further understanding of spasticity risk factors is necessary for the development and integration of early interventions and preventive measures to reduce spasticity onset and severity.

Updated perspectives on neurogenic thoracic outlet syndrome

Pain represents a foremost feature of neurogenic thoracic outlet syndrome (NTOS). Similar to other persistent pain conditions, the physical discomfort associated with NTOS can cause severe and often debilitating symptoms. In fact, those suffering from the syndrome report a quality of life impacted as significantly as those with chronic heart failure. This evidence-based literature review focuses on the classification, etiology, clinical presentation, diagnostic measures, and surgical treatment of NTOS, with a focus on nonoperative therapies such as physical modalities, pharmacological therapies, and more contemporary minimally invasive intramuscular treatments with botulinum toxin.

International consensus statement for the use of botulinum toxin treatment in adults and children with neurological impairments--introduction

Botulinum neurotoxin (BoNT) is most commonly used to reduce focal over-activity in skeletal muscle, although newer indications such as management of drooling, pain and tremor are emerging. Treatment of spasticity incorporating BoNT is usually part of an integrated multidisciplinary rehabilitation programme. Prior to initiating this therapy, specific functional limitations, goals and expected outcomes of treatment should be discussed with the patient/carers. Muscle selection and the order/priority of treatment should be agreed. Treatment goals may involve increasing active or passive function or the avoidance of secondary complications or impairment progression. This paper describes the basic science mechanisms of the action of BoNT and subsequent nerve recovery and introduces a supplement comprising the best available evidence and expert opinion from international panels on questions of assessment, indications, BoNT regimen, adjunctive therapy, expected outcomes and recommended monitoring. Speciality areas reviewed include Paediatric Lower Limb Hypertonicity, Paediatric Upper Limb Hypertonicity, Adult Lower Limb Hypertonicity, Adult Upper Limb Hypertonicity, Cervical Dystonia, Drooling and Pain and Niche Indications. There is good quality scientific evidence to support the efficacy of BoNT to reduce muscle over-activity in the limbs secondary to central nervous system disorders in adults and children, to address primary or secondary cervical dystonia, to reduce saliva flow and to treat some pain syndromes. There is emergent evidence for the efficacy of BoNT to reduce focal tremor, to treat other types of pain including neuropathic pain and also to improve function following treatment of focal muscle over-activity.

Lower limb coordination patterns in hemiparetic gait: factors of knee flexion impairment

BACKGROUND

The mechanisms altering knee flexion in hemiparetic gait may be neurological (muscle overactivity) or orthopedic (soft tissue contracture) in nature, a distinction which is difficult to ascertain clinically during gait. This study aimed to distinguish the 2 mechanisms in evaluating thigh-shank coordination, which may show instability across the gait cycle in the case of bursting rectus femoris overactivity.

METHODS

We measured thigh-shank coordination in the sagittal plane using the continuous relative phase during gait in 15 healthy subjects without and with an orthotic knee constraint (control and constrained) and 14 subjects with hemiparesis and rectus femoris overactivity before (pre) and after botulinum toxin injection.

FINDINGS

Compared with the control group, both orthopedic and neurological knee flexion limitations were associated with decreased root-mean square of continuous relative phase over swing (control, 72.9; constrained, 26.0, P<0.001; pre, 31.3, P<0.001). However, only the neurological limitation was characterized by a higher number of continuous relative phase reversals over swing (control, 2.3; pre, 4.0; P=0.001) and late stance (control, 0.6; pre, 1.7; P<0.001). Botulinum toxin injection was associated with a 40% increase in root-mean square of continuous relative phase during swing and a 41% decrease in number of continuous relative phase reversals during late stance, while peak knee flexion was increased by 31%.

INTERPRETATION

In hemiparesis, rectus femoris overactivity at swing phase is associated with alternating thigh-shank coordination in swing and late stance, which improves after botulinum toxin injection. Coordination analysis may help to distinguish neurological from orthopedic factors in knee flexion impairment.

Clinical assessment and management of spasticity: a review

Spasticity is a sign of upper motor neurone lesion, which can be located in the cerebrum or the spinal cord, and be caused by stroke, multiple sclerosis, spinal cord injury, brain injury, cerebral paresis, or other neurological conditions. Management is dependent on clinical assessment. Positive and negative effects of spasticity should be considered. Ashworth score and the modified Ashworth score are the most used scales for assessment of spasticity. These and other spasticity scales are based on assessment of resistance during passive movement. The main goal of management is functional improvement. A novel 100-point score to assess disability, function related to spasticity (Rekand disability and spasticity score) is proposed. Management of spasticity should be multimodal and should always include physiotherapy or exercise. Oral medications such as baclofen and tizanidine have limited efficacy and considerable side effects, but are easiest to use. Botulinum toxin combined with physiotherapy and/or orthopaedic surgery is effective treatment of localized spasticity. Treatment with intrathecal baclofen via programmable implanted pump is effective in generalized spasticity, particularly in the lower extremities. Neurosurgical and orthopaedic procedures may be considered in intractable cases.

Contributions of altered stretch reflex coordination to arm impairments following stroke

Patterns of stereotyped muscle coactivation, clinically referred to as synergies, emerge following stroke and impair arm function. Although researchers have focused on cortical contributions, there is growing evidence that altered stretch reflex pathways may also contribute to impairment. However, most previous reflex studies have focused on passive, single-joint movements without regard to their coordination during volitional actions. The purpose of this study was to examine the effects of stroke on coordinated activity of stretch reflexes elicited in multiple arm muscles following multijoint perturbations. We hypothesized that cortical injury results in increased stretch reflexes of muscles characteristic of the abnormal flexor synergy during active arm conditions. To test this hypothesis, we used a robot to apply position perturbations to impaired arms of 10 stroke survivors and dominant arms of 8 healthy age-matched controls. Corresponding reflexes were assessed during volitional contractions simulating different levels of gravitational support, as well as during voluntary flexion and extension of the elbow and shoulder. Reflexes were quantified by average rectified surface electromyogram, recorded from eight muscles spanning the elbow and shoulder. Reflex coordination was quantified using an independent components analysis. We found stretch reflexes elicited in the stroke group were significantly less sensitive to changes in background muscle activation compared with those in the control group (P < 0.05). We also observed significantly increased reflex coupling between elbow flexor and shoulder abductor-extensor muscles in stroke subjects relative to that in control subjects. This increased coupling was present only during volitional tasks that required elbow flexion (P < 0.001), shoulder extension (P < 0.01), and gravity opposition (P < 0.01), but not during the "no load" condition. During volitional contractions, reflex amplitudes scaled with the level of impairment, as assessed by Fugl-Meyer scores (r(2) = 0.63; P < 0.05). We conclude that altered reflex coordination is indicative of motor impairment level and may contribute to impaired arm function following stroke.

Reliability of the Tardieu Scale for assessing spasticity in children with cerebral palsy

OBJECTIVE

To measure the Tardieu Scale's reliability in children with cerebral palsy (CP) when used by raters with and without experience in using the scale, before and after training.

DESIGN

Single-center, intrarater and interrater reliability study.

SETTING

Institutional ambulatory care.

PARTICIPANTS

Referred children with CP in the pretraining phase (n=5), during training (n=3), and in the posttraining phase (n=15).

INTERVENTIONS

The Tardieu Scale involves performing passive muscle stretch at 2 velocities, slow and fast. The rater derives 2 parameters; the Spasticity Angle X is the difference between the angles of arrest at slow speed and of catch-and-release or clonus at fast speed; the Spasticity Grade Y is an ordinal variable that grades the intensity (gain) of the muscle reaction to fast stretch. In phase 1, experienced raters without formalized training in the scale graded elbow, knee, and ankle plantar flexors bilaterally, without and with a goniometer. In phase 2, after training, the experienced and nonexperienced raters graded the same muscles unilaterally.

MAIN OUTCOME MEASURES

Intrarater and interrater reliability of the Tardieu Scale.

RESULTS

After training, nonexperienced raters had mean +/- SD intrarater and interrater agreement rates across all joints and parameters of 80%+/-14% and 74%+/-16%, respectively. For experienced raters, intrarater and interrater agreement rates before training were 77%+/-13% and 66%+/-15%, respectively, versus 90%+/-8% and 81%+/-13%, respectively, after training (P<.001 for both). Specific angle measurements at the knee were less reliable for the angles of catch measured at fast speed. Across all joints, agreement rates were similar using visual or goniometric measurements.

CONCLUSIONS

Both parameters of the Tardieu Scale have excellent intrarater and interrater reliability when assessed at the elbow and ankle joints of children with CP, with no difference noted between visual and goniometric measurements. Angle measurements were less reliable at the knee joints. Training was associated with a highly significant improvement in reliability.

Lower Limb Coordination in Hemiparetic Subjects: Impact of Botulinum Toxin Injections Into Rectus Femoris

Background. Botulinum toxin (BTX) injection into rectus femoris (RF) is a therapeutic modality used to improve knee flexion during the swing phase of gait in hemiparesis. The impact of this treatment on lower limb coordination is unknown. The authors evaluated whether BTX injection into RF is associated with modifications of intersegmental coordination in hemiparesis. Methods. The authors evaluated gait in 10 control and 14 hemiparetic subjects with low peak knee flexion associated with inappropriate RF activity in mid-swing, using 3-dimensional analysis before and 1 month after BTX injection into RF (Botox, 200 units). Thigh—shank coordination was measured in the sagittal plane by averaging the continuous relative phase (CRPThigh— Shank) during each phase of the gait cycle in both lower limbs. The CRP is a validated metric that integrates angle positions and velocities of 2 limb segments to quantify their temporal—spatial coordination. Results. Before treatment, the low peak knee flexion in hemiparetic subjects (paretic limb 29 ± 9°) was associated with a decreased CRP Thigh—Shank in the paretic limb in swing (paretic limb 26.0 ± 16.6° vs controls 73.5 ± 7.4°, P < .001) and with a trend of an increased CRPThigh —Shank in the nonparetic limb over the full gait cycle (nonparetic limb 77.9 ± 14.1° vs controls 66.2 ± 19.8°, P = .083). After treatment, the CRPThigh— Shank increased by 11.9° in the swing phase of the paretic limb ( P = .002) and decreased by 8.0° over the full gait cycle ( P = .002) in the nonparetic limb. Conclusions. BTX injection into RF was associated with improved thigh—shank coordination in parts of the gait cycle, in both injected paretic and noninjected nonparetic limbs.

Abnormal volitional hip torque phasing and hip impairments in gait post stroke

The purpose of this study was to quantify how volitional control of hip torque relates to walking function poststroke. Volitional phasing of hip flexion and extension torques was assessed using a load-cell-instrumented servomotor drive system in 11 chronic stroke subjects and 5 age-matched controls. Hips were oscillated from approximately 40 degrees of hip flexion to 10 degrees of hip extension at a frequency of 0.50 Hz during three movement conditions [hips in phase (IP), 180 degrees out of phase (OP), and unilateral hip movement (UN)] while the knees and ankles were held stationary. The magnitude and phasing of hip, knee, and ankle torques were measured during each movement condition. Surface electromyography was measured throughout the legs. Over ground gait analysis was done for all stroke subjects. During robotic-assisted movement conditions, the paretic limb produced peak hip torques when agonist hip musculature was stretched instead of midway through the movement as seen in the nonparetic and control limbs (P < 0.012). However, mean torque magnitudes of the paretic and nonparetic limbs were not significantly different. Abnormalities of paretic hip torque phasing were more pronounced during bilateral movement conditions and were associated with quadriceps overactivity. The magnitude of flexion torque produced during maximal hip extension was correlated with the Fugl Meyer Score, self-selected walking speed, and maximal hip extension during over ground walking. These results suggest that hyperexcitable stretch reflexes in the paretic limb impair coordinated hip torque phasing and likely interfere with walking function post stroke.

Spastic hypertonia and movement disorders: pathophysiology, clinical presentation, and quantification

A delayed consequence of a lesion affecting the upper motor neuron pathways is the appearance of some forms of motor overactivity, including spasticity. Many of these are caused by hyperexcitability of spinal reflexes, such as stretch reflexes (spasticity, tendon hyperreflexia) or flexor withdrawal reflexes (flexor spasms), and are elicited at rest by sensory stimulation. Spastic co-contraction is probably attributable to failure of reciprocal inhibition; it occurs only during active voluntary movement and constrains such movement. The basic underlying mechanism of these changes is not clear, although a change in the balance between the inhibitory and excitatory supraspinal upper motor neuron pathways toward net excitation most likely contributes. Increased intrinsic excitability of the alpha motor neurons is another possible factor. Spastic dystonia is most often seen as the presence of tonic muscle contraction in the absence of voluntary movement or spinal reflex activation, and the underlying mechanisms are obscure. Prolonged shortening of tissues, either because of weakness or muscle contraction, leads to stiffness of the soft tissues, which contributes to hypertonia and is thus self-perpetuating, and ultimately to contracture with fixed shortening. Some of these forms of motor overactivity produce involuntary movements (hyperkinetic), eg, flexor spasms, whereas others impair movement (hypokinetic), either voluntary movement, eg, spastic co-contraction, or passive movement, eg, spasticity. Quantification has mostly focused on hypertonia, that is, increased resistance at rest to passive movement. In the upper motor neuron syndrome, hypertonia could be caused by a combination of spasticity, spastic dystonia, and soft tissue stiffness (rheologic changes). Some measures, such as the Ashworth or Modified Ashworth Scales, quantify hypertonia but are very poor at distinguishing between spasticity and soft tissue stiffness. Another, the Tardieu Scale, is better at making this distinction, but quantification of the spasticity portion of hypertonia remains difficult, at least in a clinical setting.

Comparing unilateral and bilateral upper limb training: the ULTRA-stroke program design

Background

About 80% of all stroke survivors have an upper limb paresis immediately after stroke, only about a third of whom (30 to 40%) regain some dexterity within six months following conventional treatment programs. Of late, however, two recently developed interventions - constraint-induced movement therapy (CIMT) and bilateral arm training with rhythmic auditory cueing (BATRAC) - have shown promising results in the treatment of upper limb paresis in chronic stroke patients. The ULTRA-stroke (acronym for Upper Limb TRaining After stroke) program was conceived to assess the effectiveness of these interventions in subacute stroke patients and to examine how the observed changes in sensori-motor functioning relate to changes in stroke recovery mechanisms associated with peripheral stiffness, interlimb interactions, and cortical inter- and intrahemispheric networks. The present paper describes the design of this single-blinded randomized clinical trial (RCT), which has recently started and will take several years to complete.

Methods/Design

Sixty patients with a first ever stroke will be recruited. Patients will be stratified in terms of their remaining motor ability at the distal part of the arm (i.e., wrist and finger movements) and randomized over three intervention groups receiving modified CIMT, modified BATRAC, or an equally intensive (i.e., dose-matched) conventional treatment program for 6 weeks. Primary outcome variable is the score on the Action Research Arm test (ARAT), which will be assessed before, directly after, and 6 weeks after the intervention. During those test sessions all patients will also undergo measurements aimed at investigating the associated recovery mechanisms using haptic robots and magneto-encephalography (MEG).

Discussion

ULTRA-stroke is a 3-year translational research program which aims (1) to assess the relative effectiveness of the three interventions, on a group level but also as a function of patient characteristics, and (2) to delineate the functional and neurophysiological changes that are induced by those interventions.

The outcome on the ARAT together with information about changes in the associated mechanisms will provide a better understanding of how specific therapies influence neurobiological changes, and which post-stroke conditions lend themselves to specific treatments.

Trial Registration

The ULTRA-stroke program is registered at the Netherlands Trial Register (NTR, http://www.trialregister.nl, number NTR1665).

New clinical and research trends in lower extremity management for ambulatory children with cerebral palsy

Cerebral palsy (CP) is the most prevalent physical disability in childhood and includes a group of disorders with varying manifestations. This article focuses on current and future intervention strategies for improving mobility and participation during the lifespan for ambulatory children with CP. The provision and integration of physical therapy and medical and orthopedic surgery management focused primarily on the lower extremities are discussed here. Some of the newer trends are more intense and task-related exercise strategies, greater precision in tone identification and management, and a shift towards musculoskeletal surgery that focuses more on promoting dynamic bony alignment and less on releasing or lengthening tendons. Advances in basic and clinical science and technology development are changing existing paradigms and offering renewed hope for improved functioning for children with CP who face a lifelong disability with unique challenges at each stage in life.

Contractures and involuntary muscle overactivity in severe brain injury

PRIMARY OBJECTIVE

The aim of the present study was to evaluate the association of contractures with an increase or reduction of non-spastic muscle overactivity due to severe cerebral damage.

METHODS AND PROCEDURES

Forty-five patients with tetraparesis after severe cerebral damage were investigated. Three groups were defined based on the presence of spasticity (revealed as resistance to passive stretch (= hypertonia)), and the presence of contracture of the relevant knee joint: Group(s) (17 patients with hypertonia without contracture), Group(s+c) (20 patients with hypertonia and contracture), and Group(c) (eight patients without hypertonia and with contracture). In all groups spontaneous involuntary muscle activity was assessed continuously over a 12-hour period through isometric measurement of knee joint flexion torque. A mathematical algorithm differentiated an hourly muscle activity spectrum (PI(h)). The frequency of peaks (peaks(h)) from the activity spectrum was determined.

MAIN OUTCOMES AND RESULTS

We revealed that Group(s) had higher PI(h) and more frequent peaks(h) compared with Group(s+c) and Group(c) (p<0.05). Group(c) had comparable PI(h) and peaks(h) compared with Group(s+c) (p>0.05).

CONCLUSION

The presence of contractures was associated with lower involuntary muscle overactivity in terms of lower PI(h) and less frequent peaks(h), indicating that contractures may be associated with reduced non-spastic positive features of the upper motor neurone syndrome in patients with severe brain damage.

Knee resistance during passive stretch in patients with hypertonia

The aims of the study were to determine by a portable method (1) whether velocity-dependent changes in knee resistance in patients with spastic paresis differ from those in non-disabled subjects, and (2) whether biomechanical measures of resistance can differentiate between neural and other factors that contribute to hypertonia (increased resistance). Biomechanical (hand-hold dynamometer, electrogoniometer) and bioelectrical (EMG) measures of resistance were evaluated under static (slow stretch) and dynamic (fast stretch) conditions in twenty patients with hypertonia and 19 non-disabled subjects. Measures calculated for non-disabled subjects (control limbs) were compared to those calculated for patients (spastic limbs). Biomechanical measures of resistance did not differ strongly between groups of spastic and control limbs and between spastic limbs having different origins of knee hypertonia (neural vs. other), due to substantial variability. In contrary the static and dynamic bioelectrical measures of muscles activation were substantially larger in spastic limbs than in control limbs (p<0.05). The variability of biomechanical measures of resistance was due to varied patterns of muscle activation in response to stretch. We concluded that the biomechanical measures of hypertonia did not discriminate spastic patients from non-disabled subjects. To classify various types of knee hypertonia, the portable method should include not only analysis of biomechanical but also EMG characteristics of hypertonia. It is expected that the functional status of patients would be better predicted using clinical and quantitative measures of impairment if different classes of hypertonia (defined by different patterns of activation) were analyzed separately rather than analyzing the heterogeneous patient population as a whole.

Botulinum toxin dilution and endplate targeting in spasticity: a double-blind controlled study

OBJECTIVE

To determine the effects of botulinum neurotoxin type A (BTX-A) dilution and endplate-targeting in spastic elbow flexors.

DESIGN

Double blind randomized controlled trial; 4-month follow-up after a 160-unit injection of BTX-A into spastic biceps brachii (4 sites). Randomization into: group 1: 100 mouse units (MU)/mL dilution, 0.4cc/site, 4-quadrant injection; group 2: 100MU/mL dilution, 0.4cc/site, 4 sites along endplate band; group 3: 20MU/mL dilution, 2cc/site, 4-quadrant injection (n=7 per group).

SETTING

Institutional tertiary care ambulatory clinic.

PARTICIPANTS

Referred sample of 21 adults with spastic hemiparesis. No participant withdrew due to adverse effects.

INTERVENTION

A 160-unit injection of BTX-A of different dilutions and locations into biceps brachii.

MAIN OUTCOME MEASURES

Primary: agonist and antagonist (cocontraction) mean rectified voltage (MRV) of elbow flexors/extensors during maximal isometric flexion/extension; secondary: maximal voluntary power of elbow flexion/extension; spasticity angle and grade in elbow flexors/extensors (Tardieu Scale); active range of elbow extension/flexion.

RESULTS

BTX-A injection overall reduced agonist flexor MRV (-47.5%, P<0.0001), antagonist flexor MRV (-12%, P=.037), antagonist extensor MRV (-19%, P<.01), flexion maximal voluntary power (-33%, P<.001), elbow flexor spasticity angle (-30%, P<.001) and grade (-17%, P=.03), and increased extension maximal voluntary power (24%, P=.037) and active range of elbow extension (5.5%, 8 degrees , P=.002). Agonist and antagonist flexor MRV reductions in group 3 (-81% and -31%) were greater than in groups 1 and 2, whereas increase in active range of elbow extension was greater in group 2 (10%) than in groups 1 and 3 (P<.05, analysis of covariance [ANCOVA]). Elbow flexor spasticity was significantly reduced in groups 2 and 3 only (P<.05, ANCOVA).

CONCLUSIONS

In spastic biceps, high-volume or endplate-targeted BTX-A injections achieve greater neuromuscular blockade, cocontraction and spasticity reduction, and active range of elbow extension improvement, than low volume, nontargeted injections.

Roles of reflex activity and co-contraction during assessments of spasticity of the knee flexor and knee extensor muscles in children with cerebral palsy and different functional levels

BACKGROUND AND PURPOSE

Spasticity is a common impairment in children with cerebral palsy (CP). The purpose of this study was to examine differences in passive resistive torque, reflex activity, coactivation, and reciprocal facilitation during assessments of the spasticity of knee flexor and knee extensor muscles in children with CP and different levels of functional ability.

SUBJECTS

Study participants were 20 children with CP and 10 children with typical development (TD). The 20 children with CP were equally divided into 2 groups: 10 children classified in Gross Motor Function Classification Scale (GMFCS) level I and 10 children classified in GMFCS level III.

METHODS

One set of 10 passive movements between 25 and 90 degrees of knee flexion and one set of 10 passive movements between 90 and 25 degrees of knee flexion were completed with an isokinetic dynamometer at 15 degrees /s, 90 degrees /s, and 180 degrees /s and concurrent surface electromyography of the vastus lateralis and medial hamstring muscles.

RESULTS

Children in the GMFCS level III group demonstrated significantly more peak knee flexor torque with passive movements at 180 degrees /s than children with TD. Children in the GMFCS level I and level III groups demonstrated significantly more repetitions with medial hamstring muscle activity, vastus lateralis muscle activity, and co-contraction than children with TD during the assessment of knee flexor spasticity at a velocity of 180 degrees /s.

DISCUSSION AND CONCLUSION

Children with CP and more impaired functional mobility may demonstrate more knee flexor spasticity and reflex activity, as measured by isokinetic dynamometry, than children with TD. However, the finding of increased reflex activity with no increase in torque in the GMFCS I group in a comparison with the TD group suggests that reflex activity may play a less prominent role in spasticity.

Effects of stretching and heat treatment on hamstring extensibility in children with severe mental retardation and hypertonia

Objectives: To examine the effect of heat and duration of stretching on the extensibility of hamstring muscles and their electromyographic responses to passive stretch in children with hypertonia and severe mental retardation.

Design: Randomized cross-over trial.

Setting: Developmental disability unit in a local hospital.

Participants: Twenty-nine subjects (9 females) with ages ranged from 4 to 13 years with spastic and/or dystonic hypertonia and hamstring tightness.

Interventions: Subjects received four treatment sessions in random order with each consisting of five repetitions of stretching: (A) 10-second stretching, (B) 30-second stretching, (C) hot pack followed by 10-second stretching, and (D) hot pack followed by 30-second stretching. Each treatment session comprised five repetitions of stretch and successive treatments were separated by at least 24 hours.

Main outcome measures: The distance between greater trochanter and lateral malleolus and hamstring electromyographic (EMG) activity during passive knee extension stretching.

Results: Two-way ANOVA showed a larger increase in hamstring extensibility in conditions C and D (1.3 ± 1.1 cm) than conditions A and B (0.7 ± 0.9 cm) (P<0.001). For the EMG recordings, conditions B and D (-25.1 ± 58.4μV) had greater decrease than conditions A and C (-3.5 ± 36.6 μV) (P= 0.039).

Conclusions: Heat application to the hamstrings before stretching could result in greater increase in extensibility than stretching alone in children with hypertonia and severe mental retardation. Stretching could promote relaxation of the hamstring muscles regardless of prior heat treatment. Stretching sustained for 30 seconds led to greater relaxation than that for 10 seconds.

Spastic paretic hemifacial contracture in multiple sclerosis: a neglected clinical and EMG entity

Background

Spastic paretic hemifacial contracture (SPHC) is an uncommon condition, originally described as a sign of brainstem neoplasia, characterized by sustained unilateral contraction of the facial muscles associated with mild ipsilateral facial paresis. SPHC has only rarely been reported in the context of multiple sclerosis (MS). To further study and assess the frequency of SPHC in patients with MS.

Methods

We screened clinically 500 consecutive patients with MS for the presence of SPHC and further studied electrophysiologically any cases identified.

Results

We identified two patients who developed the condition during the course of an MS relapse. The estimated frequency of the condition was 0.4%. Both patients had relapsing–remitting MS. SPHC was characterized on Electromyography (EMG) by continuous resting activity of irregularly firing motor unit potentials, associated with impaired recruitment of motor units on voluntary contraction. Myokymic discharges were not present. Blink reflex studies were partly consistent with midpontine lesions in the vicinity of the facial nucleus ipsilateral to SPHC. MRI showed lesions in the ipsilateral dorsolateral midpontine tegmentum.

Conclusions

SPHC constitutes a rare but distinct clinical and EMG entity in patients with MS.

Stretch reflex coupling between the hip and knee: implications for impaired gait following stroke

Individuals with hemiparetic stroke often exhibit an abnormal coupling between the frontal plane of the hip and saggital plane of the knee during gait. The purpose of this study was to determine if stretch sensitive reflexes, which are known to be altered following stroke, exhibit similar coupling between the muscles of the hip and knee in the post-stroke population. Eighteen subjects were recruited for this study including ten with hemiparesis resulting from stroke and eight unimpaired, age-matched controls. A servomotor was used to apply ramp and hold perturbations to both the hip and knee joints in separate sessions and electromyographic activity was recorded in eight muscles of the lower limb. Hip abduction perturbations elicited abnormal activation in rectus femoris (RF) in seven of ten stroke subjects with amplitudes ranging from 3.2 to 12.5% of the maximum voluntary contraction (MVC). Only two of eight control subjects exhibited any activity in RF and these responses were only 2.1 and 2.7% of MVC. To determine if the responses in the stroke group were a result of muscle stretch, a musculoskeletal model was used to simulate the experimental abduction perturbations and estimate muscle length changes. The simulation revealed that RF should be shortened by the perturbations and this suggests that the response was not likely due to direct stretch. Moreover, knee flexion perturbations elicited responses in the hip adductors (AL) with a mean amplitude of 5.1 +/- 3.8% of MVC across all stroke subjects while no significant responses were recorded in controls. The presence of a reciprocal, reflex-mediated coupling between RF and AL following stroke suggests that changes in the excitability of spinal networks may contribute to the development of abnormal inter-joint coordination patterns observed during hemiparetic gait.

Lower extremity passive range of motion in community-ambulating stroke survivors

BACKGROUND

Physical therapists may prescribe stretching exercises for individuals with stroke to improve joint integrity and to reduce the risk of secondary musculoskeletal impairment. While deficits in passive range of motion (PROM) exist in stroke survivors with severe hemiparesis and spasticity, the extent to which impaired lower extremity PROM occurs in community-ambulating stroke survivors remains unclear. This study compared lower extremity PROM in able-bodied individuals and independent community-ambulatory stroke survivors with residual stroke-related neuromuscular impairments. Our hypothesis was that the stroke group would show decreased lower extremity PROM in the paretic but not the nonparetic side and that decreased PROM would be associated with increased muscle stiffness and decreased muscle length.

METHODS

Individuals with chronic poststroke hemiparesis who reported the ability to ambulate independently in the community (n = 17) and age-matched control subjects (n = 15) participated. PROM during slow (5 degrees/sec) hip extension, hip flexion, and ankle dorsiflexion was examined bilaterally using a dynamometer that measured joint position and torque. The maximum angular position of the joint (ANGmax), torque required to achieve ANGmax (Tmax), and mean joint stiffness (K) were measured. Comparisons were made between able-bodied and paretic and able-bodied and nonparetic limbs.

RESULTS

Contrary to our expectations, between-group differences in ANGmax were observed only during hip extension in which ANGmax was greater bilaterally in people post-stroke compared to control subjects (P

CONCLUSION

This study demonstrates that community-ambulating stroke survivors with residual neuromuscular impairments do not have decreased lower extremity PROM caused by increased muscle stiffness or decreased muscle length. In fact, the population of stroke survivors examined here appears to have more hip extension PROM than age-matched able-bodied individuals. The clinical implications of these data are important and suggest that lower extremity PROM may not interfere with mobility in community-ambulating stroke survivors. Hence, physical therapists may choose to recommend activities other than stretching exercises for stroke survivors who are or will become independent community ambulators.

Collapse

Key Words

• cerebral vascular accident (cva)
• hemiparesis
• muscle
• range of motion (rom)
• spasticity

Collapse

MESH Headings

• Adult
• Aged
• Ankle Joint/physiopathology
• Case-Control Studies
• Cohort Studies
• Female
• Hip Joint/physiopathology
• Humans
• Lower Extremity/physiopathology
• Male
• Middle Aged
• Paresis/etiology
• Paresis/physiopathology
• Paresis/rehabilitation
• Range of Motion, Articular/physiology
• Stroke/complications
• Stroke/physiopathology
• Stroke Rehabilitation
• Walking/physiology

Collapse

Grants

• F32 HD044299 NICHD NIH HHS
• 1 F32 HD044299-01 NICHD NIH HHS

Collapse

Affiliation(s)

Sheila Schindler-Ivens Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Davalyn Desimone
Sarah Grubich
Carolyn Kelley
Namita Sanghvi
David A Brown

Collapse

Intrathecal baclofen for spasticity-related pain in amyotrophic lateral sclerosis: Efficacy and factors associated with pain relief

Clinical signs and symptoms of spasticity include hypertonia, involuntary movements (spasms, clonus), decreased range of motion, contractures, and often spasm-related pain. When spasticity is refractory to medical management, patients may be referred for intrathecal baclofen (ITB) pump placement. We reviewed a cohort of amyotrophic lateral sclerosis (ALS) patients with intractable spasticity requiring ITB to further define the impact of ITB on pain relief in this patient population. From 2003 to 2005, eight patients (mean age 43.8 years; 5 men, 3 women) with ALS received ITB for pain associated with intractable spasticity at our institution. Mean disease duration preoperatively was 47.4 months, mean follow-up was 9.8 months, and pain was evaluated using a 0-10 scoring system. All patients experienced spasticity relief in response to a preoperative bolus test injection of ITB (25-50 microg) via lumbar puncture. Following ITB pump placement, the average reduction of pain was 54% (P = 0.0082). Six patients (75%) experienced pain score reduction, three of whom had complete pain relief. Postoperative pain reduction was predicted by the degree of pain reduction following preoperative ITB test injection. These results support ITB as a treatment modality for pain associated with spasticity in ALS.

Epimuscular myofascial force transmission between antagonistic and synergistic muscles can explain movement limitation in spastic paresis

Details and concepts of intramuscular, extramuscular and intermuscular myofascial force transmission are reviewed. Some new experimental data are added regarding myofascial force transmission between antagonistic muscles across the interosseal membrane of the lower hind limb of the rat. Combined with other result presented in this issue, it can be concluded that myofascial force transmission occurs between all muscles within a limb segment. This means that force generated within sarcomeres of an antagonistic muscle may be exerted at the tendon of target muscle or its synergists. Some, in vivo, but initial indications for intersegmental myofascial force transmission are discussed. The concept of myofascial force transmission as an additional load on the muscle proved to be fruitful in the analysis of its muscular effects. In spastic paresis and for healthy muscles distal myofascial loads are often encountered, but cannot fully explain the movement limitations in spastic paresis. Therefore, the concept of simultaneous and opposing myofascial loads is analyzed and used to formulate a hypothesis for explaining the movement limitation: Myofascially transmitted antagonistic force is borne by the spastic muscle, but subsequently transmitted again to distal tendons of synergistic muscles.

Motor unit discharge pattern and conduction velocity in patients with upper motor neuron syndrome

Motor unit properties were analyzed in patients with upper motor neuron syndrome (UMNS). Multi-channel surface electromyographic (EMG) signals were recorded for 300s from the biceps brachii muscle of seven male subacute patients (time from lesion, mean+/-SE, 4.9+/-1.0 months). In three patients, both arms were investigated, leading to 10 recorded muscles. Patients were analyzed in rest-like condition with motor units activated due to pathological muscle overactivity. For a total of 12 motor units, the complete discharge pattern was extracted from EMG decomposition. Interpulse interval variability was 7.8+/-0.9%. At minimum discharge rate (6.4+/-0.4 pulses per second, pps), conduction velocity was smaller than at maximum discharge rate (12.0+/-0.9pps) in all motor units (3.60+/-0.21m/s vs. 3.84+/-0.20m/s). Conduction velocity changed by 1.35+/-0.48% (different from zero, P<0.01) for each increase of 1pps in discharge rate. It was concluded that conduction velocity of low-threshold motor units in subacute patients with UMNS had similar values as reported in healthy subjects and was positively correlated to instantaneous discharge rate (velocity recovery function of muscle fibers).

The phenomenon of spasticity: a pathophysiological and clinical introduction to neuromodulation therapies

Spasticity is part of the complex clinical picture which results from the upper motor neuron impairment. The underlying mechanisms that produce the automatic overactivity of the muscle groups may manifest themselves as either passive movements dependent on the exerted velocity or persistent muscle overactivity in the form of spastic dystonia. The therapeutic management of spasticity is closely related to the aims of rehabilitation; these include avoidance of complications, restoration of movement, re-education of motion and gait, development of self-dependency, and social integration, as well as modification and reorganization of the cortical brain map. The latter is achieved through long-term learning processes which are subserved by new neurophysiological dynamics. and the mechanisms of neuroplasticity which develop during neural regeneration.

Formation of neutralizing antibodies in patients receiving botulinum toxin type A for treatment of poststroke spasticity: a pooled-data analysis of three clinical trials

OBJECTIVE

The purpose of this study was to investigate the incidence of neutralizing antibody (NAb) formation in patients with poststroke spasticity treated with a specific formulation of botulinum toxin type A (BoNTA).

METHODS

Data from 3 previous clinical trials of BoNTA in patients with upper and/or lower limb spasticity were pooled and evaluated. Study 1 was a randomized, double-blind, placebo-controlled, multicenter trial of BoNTA in patients aged >/=21 years who had experienced a stroke >6 months before the initiation of the study. Study 2 was an open-label extension of study 1. Study 3 was a randomized, double-blind, multicenter trial of a specific BoNTA formulation in patients aged >/= 21 years who had experienced a stroke >/=6 weeks before study entry. Patients with a fixed contracture of the studied limb were excluded from participation in studies 1 and 2. Serum samples were obtained from each patient before each BoNTA treatment and at the end of each study. The mouse protection assay (MPA) was used for detection of NAbs to BoNTA in serum.

RESULTS

A total of 235 individual patients with post-stroke spasticity were enrolled in the 3 trials, including 126, 111 (all of whom participated in study 1), and 109 in studies 1, 2, and 3, respectively. Study 1 had an equal (50.0%) distribution of male and female patients (63/63). The distribution of male and female patients was 56 (50.5%) and 55 (49.5%), respectively, in study 2, and 55 (50.5%) and 54 (49.5), respectively, in study 3. The mean (SD) ages of patients in studies 1, 2, and 3 were 61.4 (13.8), 61.5 (14.1), and 58.5 (13.9) years, respectively. The MPA was used for detection of NAbs to BoNTA in the serum samples of 191 patients, including 64 from study 1, 111 from study 2 (55 of these patients were placebo recipients and 56 received their first BoNTA injection in study 1), and 72 (a sample was not obtained for 1 patient who had not received an injection) from study 3. The median number of BoNTA treatments received by these patients was 2 (range, 1-4 treatments) over a period lasting from 12 to 42 weeks. The mean dose of BoNTA was 241 U (range, 100-400 U), with a maximum dose of 960 U in any 1 patient. NAbs to BoNTA were detected in the serum sample of 1/191 (0.5%) patient who had participated in studies 1 and 2. Based on muscle-tone scores (3 and 4 for wrist and fingers, respectively) on a 5-point Ashworth Scale (0 = none to 4 = severe), the patient did not appear to exhibit a clinical response to BoNTA at any time during the studies.

CONCLUSION

Formation of NAbs was rare (1/191) in this group of adults with poststroke spasticity from three 12- to 42-week clinical trials who received >/=1 treatment with a specific BoNTA formulation at doses ranging from 100 to 400 U.

The nature of hand motor impairment after stroke and its treatment

Hand motor impairments may be viewed as 1) a deficit in motor execution, resulting from weakness, spasticity, and abnormal muscle synergies, and/or 2) a deficit in higher-order processes, such as motor planning and motor learning, which lead to poorly formed sensorimotor associations that lead to impaired motor control. Although weakness and spasticity impede motor execution, strengthening and tone reduction represent simplistic solutions to the deficit in motor control after stroke. Deficits in hand motor control are better appreciated by examining the coordination of fingertip forces and movements during natural movements, and suggest that impairments in motor learning and planning are fundamental impediments to motor recovery following stroke. However, despite an explosion in the number of therapeutic protocols based on the principles of motor learning, little is known about the types of motor learning impairment that occur after stroke and how lesion location may influence motor relearning.

Motor neuron inhibition-based gene therapy for spasticity

Spasticity is a condition resulting from excess motor neuron excitation, leading to involuntary muscle contraction in response to increased velocity of movement, for which there is currently no cure. Existing symptomatic therapies face a variety of limitations. The extent of relief that can be delivered by ablative techniques such as rhizotomy is limited by the potential for sensory denervation. Pharmacological approaches, including intrathecal baclofen, can be undermined by tolerance. One potential new approach to the treatment of spasticity is the control of neuromuscular overactivity through the delivery of genes capable of inducing synaptic inhibition. A variety of experiments in cell culture and animal models have demonstrated the ability of neural gene transfer to inhibit neuronal activity and suppress transmission. Similarly, enthusiasm for the application of gene therapy to neurodegenerative diseases of motor neurons has led to the development of a variety of strategies for motor neuron gene delivery. In this review, we discuss the limitations of existing spasticity therapies, the feasibility of motor neuron inhibition as a gene-based treatment for spasticity, potential inhibitory transgene candidates, strategies for control of transgene expression, and applicable motor neuron gene targeting strategies. Finally, we discuss future directions and the potential for gene-based motor neuron inhibition in therapeutic clinical trials to serve as an effective treatment modality for spasticity, either in conjunction with or as a replacement for presently available therapies.

The spinal pathophysiology of spasticity--from a basic science point of view

Spasticity is a term, which was introduced to describe the velocity-sensitive increased resistance of a limb to manipulation in subjects with lesions of descending motor pathways. This distinguishes spasticity from the changes in passive muscle properties, which are often seen in these patients, but are not velocity-sensitive. Increased excitability of the stretch reflex is thus a central component of the definition of spasticity. This review describes changes in cellular properties and transmission in a number of spinal reflex pathways, which may explain the increased stretch reflex excitability. The review focuses mainly on results derived from the use of non-invasive electrophysiological techniques, which have been developed during the past 20-30 years to investigate spinal neuronal networks in human subjects, but work from animal models is also considered. The reflex hyperexcitability develops over several months following the primary lesion and involves adaptation in the spinal neuronal circuitries caudal to the lesion. In animal models, changes in cellular properties (such as 'plateau potentials') have been reported, but the relevance of these changes to human spasticity has not been clarified. In humans, numerous studies have suggested that reduction of spinal inhibitory mechanisms (in particular that of disynaptic reciprocal inhibition) is involved. The inter-subject variability of these mechanisms and the lack of objective quantitative measures of spasticity have impeded disclosure of a clear causal relationship between the alterations in the inhibitory mechanisms and the stretch reflex hyperexcitability. Techniques which make such a quantitative measure possible as well as longitudinal studies where development of reflex excitability and changes in the inhibitory mechanisms are followed over time are in great demand.

Decreased capillarization and a shift to fast myosin heavy chain IIx in the biceps brachii muscle from young adults with spastic paresis

Muscle spasticity and paresis are conditions that occur secondary to upper motor neuron lesions. The co-existence of decreased motor unit recruitment and intermittent over-activity generates confusion concerning the effect on muscle fiber characteristics. In order to increase the knowledge about the effect of upper motor lesion on capillarization and muscle fiber composition, the biceps brachii muscle from seven young adults with long duration of spastic paresis and seven age-matched controls were analyzed using morphological and enzyme- and immuno-histochemical techniques. The spastic muscles had a 38% lower capillary density (p=0.002), 30% fewer capillaries around each muscle fiber (p=0.02), and 16% fewer capillaries when related to the fiber size (p=0.04). The frequency of fibers expressing myosin heavy chain (MyHC) IIx increased (30% vs. 4%, p=0.006), while the percentage of fibers expressing MyHC I and MyHC IIa, respectively, decreased (22% vs. 46% and 7% vs. 29%, p<0.01). The high proportion of muscle fibers with low oxidative capacity and low capillary supply indicates that biceps brachii muscle from patients with upper motor lesions fatigue more easily than normal controls. We also observed a significantly higher variability in fiber size for fibers expressing MyHC I (p<0.04), and, in three of the subjects, a small amount of small fibers expressing developmental MyHCs was found. These results suggest that, although intermittent stretch reflex contractions might have an impact on the muscle characteristics in spastic paresis, the muscle phenotypic properties are more adapted to decreased voluntary motor unit recruitment.

Botulinum toxin-A injections for spastic toe clawing

Spastic toe clawing describes extension at the metatarsophalangeal joints of the feet, flexion at the proximal interphalangeal joints and flexion at the distal interphalangeal joints that results from upper motor neuron lesions, such as stroke, intracranial hemorrhage, cervical myelopathy and brain tumors. Even though toe clawing is often asymptomatic, it can be painful. Previous studies have described the efficacy of injections of botulinum toxin type-A (BTX-A) to the long flexors of the toes, but this is often unsatisfactory as high dosages (up to 175 units) have been required, and patients often report significant residual toe clawing. We performed an open label, prospective study to assess the efficacy of BTX-A injections, targeting the long and short flexors of the toes, performed with electrical (motor point) stimulation under electromyographic guidance. Outcome measures, which included timed walking over 20m, objective assessment of toe clawing (modified Ashworth scale and a visual analog scale rating) and patient assessment of functional disability, were assessed before injections and at six-weeks' follow-up. Seven patients (five male and two female) of mean age 51 (range 38-70) were recruited. Four had spasticity from underlying intracranial hemorrhage, the remaining three from cerebral infarct, astrocytoma and post-traumatic cervical myelopathy. The total dose of BTX-A injected for toe clawing ranged from 40 to 90 units. Improvements were observed in all outcome measures except timed walking. Injecting BTX-A to the long and short flexors of the toes, with electrical stimulation under electromyographic guidance, is well tolerated and efficacious in the treatment of toe clawing from spasticity, allowing for lower dosages to be used.

Patterns of impairment in digit independence after subcortical stroke

The nature of impairment in hand motor control after stroke and its relationship to hand function are still not well understood. In this study, we investigated digit independence in patients with subcortical stroke (n = 8) and moderate hand impairment, defined by wrist and hand Fugl-Meyer scale scores < or =25/33, and age-matched controls (n = 8). Subjects made cyclical flexion-extension movements of an instructed digit while keeping the other digits as still as possible. Movements of the metacarpo-phalangeal (MCP) joints of the five digits were measured using an instrumented glove. The ability to move an instructed digit individually (individuation index), and the ability to keep a noninstructed digit as still as possible (stationarity index) were determined for each digit. Contrary to the finding of normal thumb individuation in a recent study of patients with variable hand motor impairment after stroke, we found that independent movement for all digits was significantly impaired, although individuation and stationarity were differentially affected for each digit. All the digits, including the thumb, showed a similar impairment in individuation. In contrast, stationarity was affected in a digit-dependent pattern: the thumb was affected least, and the middle finger was most impaired. Stroke subjects did not extend their digits fully to the baseline position, and the angular displacement at maximum digit extension correlated significantly with digit individuation. Contrary to expectation, digit independence correlated weakly with clinical tests of hand function, which emphasize grasp. This suggests that corticospinal projections might be separated with respect to function rather than finger topography.