Biomechanic characteristics of patients with spastic and dystonic hypertonia in cerebral palsy11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated

Learning ballet technique modulates the stretch reflex in students with cerebral palsy: case series

BACKGROUND

Cerebral palsy (CP) is considered the most prevalent developmental motor disorder in children. There is a need for training programs that enhance motor abilities and normalize function from an early age. Previous studies report improved motor outcomes in dance interventions for CP. Investigating the neurophysiological mechanisms underlying such improvements is necessary for efficient and safe intervention design. This study reports changes in stretch reflex responses as the primary neurophysiological motor outcome of a targeted ballet class intervention.

RESULTS

A case series of participants with mixed spastic and dyskinetic CP (n = 4, mean age = 12.5 years, SD = 6.9S years, three female, one male) who learned ballet technique in a course of one-hour classes twice per week for six weeks is presented. Changes in stretch reflex responses and in clinical motor tests as secondary outcomes were observed after the course and at one-month follow-up. Quantitative measures of elbow or ankle stretch reflex were obtained using electromyography and electrogoniometry. The joint angle of the stretch reflex onset varied across velocities of stretch, and its variability decreased after the intervention. Within-subject tests of the central tendency of stretch reflex angle coefficients of variation and frequency distribution demonstrated significant changes (p-values < 0.05). Secondary outcomes included the Quality of Upper Extremity Skills Test (QUEST), Pediatric Balance Scale (PBS), Modified Tardieu Scale (MTS), Dyskinesia Impairment Scale (DIS), and Selective Control Assessment of the Lower Extremity (SCALE). All the participants demonstrated improvements larger than the minimal clinical important difference (MCID) or the smallest detectable difference (SDD), as applicable.

CONCLUSIONS

Evidence of changes in the stretch reflex responses in these four cases of mixed CP was observed. The observed variability in the stretch reflex responses may be due to the dyskinetic component of the mixed CP presentations. More studies with a larger sample size and longer duration of learning and practice of ballet technique are necessary to establish the extent of possible modulation and adaptation of the stretch reflex response as a neurophysiological basis for observed improvements in clinical measures.

TRIAL REGISTRATION

This study was registered in the Clinical Trials Protocol Registration and Results System (NCT04237506, January 17, 2020).

Dystonia assessment in children with cerebral palsy and periventricular leukomalacia

OBJECTIVE

To describe the frequency, motor phenotype, clinical patterns and functional consequences of dystonia in patients with cerebral palsy (CP) in the setting of periventricular leukomalacia.

METHODS

Retrospective analysis of a cohort of 31 patients with CP and periventricular leukomalacia. Gross Motor Function Classification System (GMFCS) and Manual Ability Classification System (MACS) were used to classify functional ability. Spasticity was rated using the Modified Ashworth Scale. Presence of dystonia was assessed by reviewing video recordings, and its severity by using the Burke-Fahn-Marsden Dystonia Rating Scale.

RESULTS

All patients showed evidence of dystonia involving upper and/or lower limbs, neck, trunk, mouth and eyes in order of frequency. In 29% of patients dystonia involved only the limbs and in 71% it was multifocal. Dystonia severity ranged from slight to severe. Severity and distribution of dystonia did not correlate with gender, age, weeks of gestation or duration of neonatal unit stay. GMFCS and MACS correlated with dystonia but not with spasticity.

CONCLUSIONS

Severity of dystonia, but not spasticity is associated with the severity of motor functional disability in CP patients with periventricular leukomalacia and demonstrates the key role of dystonia in the motor function of these patients.

Clinical Presentation of Spasticity and Passive Range of Motion Deviations in Dyskinetic Cerebral Palsy in Relation to Dystonia, Choreoathetosis, and Functional Classification Systems

Objectives: To map the presence, severity, and distribution of spasticity and passive range of motion (pROM) deviations in dyskinetic cerebral palsy (DCP), and to explore their relation with dystonia, choreoathetosis, and functional abilities.Methods: This cross-sectional study included 53 participants with DCP. Spasticity was assessed with the Modified Ashworth Scale, limited- and increased pROM (hypermobility) with a goniometer, dystonia and choreoathetosis with the Dyskinesia Impairment Scale, gross motor and manual abilities with corresponding functional classification systems.Results: Spasticity and limited pROM were correlated with dystonia of the upper limbs (0.41< r_s<0.47, <0.001 < p < .002) and lower limbs (0.31< r_s<0.41, 0.002 < p < .025), and both functional systems of gross motor (0.32< r_s<0.51, <0.001 < p < .018) and fine manual abilities (0.34< r_s<0.44, 0.001 < p < .014). Hypermobility is correlated only with choreoathetosis of the lower limbs (0.44, p = .001).Conclusions: Coexisting spasticity and pROM deviations in DCP are functionally limiting and should be addressed accordingly. Hypermobility may lead to an increased luxation risk.

Effect of Transcranial Direct Current Stimulation Combined With Xbox-Kinect Game Experience on Upper Limb Movement in Down Syndrome: A Case Report

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique used to enhance local synaptic efficacy and modulate the electrical activity of the cortex in neurological disorders. Researchers have sought to combine this type of stimulation with well-established therapeutic modalities, such as motor training involving Xbox Kinect games, which has demonstrated promising results. Thus, this study aimed to determine whether tDCS can enhance upper limb motor training in an eight-year-old child with Down Syndrome (DS) (cognitive age: five years, based on the Wechsler Intelligence Scale for Children). The evaluations consisted of three-dimensional analysis of upper limb kinematics during a reaching task performed before, after10 session, and one month after the intervention. The intervention protocol involved 1 20-min sessions of tDCS over the primary motor cortex at an intensity of 1 mA during Xbox Kinect game training involving an upper limb motor task. The analysis of the kinematic data revealed that in the pre-intervention evaluation, the dominant limb executed the task slowly and over a long path. These aspects improved at the post-intervention and follow-up evaluations, as demonstrated by the shorter total movement duration (3.05 vs. 1.58 vs. 1.52 s, respectively). Similar changes occurred with the non-dominant upper limb; a significant increase in movement velocity at the post-intervention and follow-up evaluations was observed (0.53 vs. 0.54 vs. 0.85 m/s, respectively). The present case report offers preliminary data from a protocol study, and the results confirm the notion that anodal tDCS combined with upper limb motor training leads to improvements in different kinematic variables.

Instrumented assessment of motor function in dyskinetic cerebral palsy: a systematic review

BACKGROUND

In this systematic review we investigate which instrumented measurements are available to assess motor impairments, related activity limitations and participation restrictions in children and young adults with dyskinetic cerebral palsy. We aim to classify these instrumented measurements using the categories of the international classification of functioning, disability and health for children and youth (ICF-CY) and provide an overview of the outcome parameters.

METHODS

A systematic literature search was performed in November 2019. We electronically searched Pubmed, Embase and Scopus databases. Search blocks included (a) cerebral palsy, (b) athetosis, dystonia and/or dyskinesia, (c) age 2-24 years and (d) instrumented measurements (using keywords such as biomechanics, sensors, smartphone, and robot).

RESULTS

Our search yielded 4537 articles. After inspection of titles and abstracts, a full text of 245 of those articles were included and assessed for further eligibility. A total of 49 articles met our inclusion criteria. A broad spectrum of instruments and technologies are used to assess motor function in dyskinetic cerebral palsy, with the majority using 3D motion capture and surface electromyography. Only for a small number of instruments methodological quality was assessed, with only one study showing an adequate assessment of test-retest reliability. The majority of studies was at ICF-CY function and structure level and assessed control of voluntary movement (29 of 49) mainly in the upper extremity, followed by assessment of involuntary movements (15 of 49), muscle tone/motor reflex (6 of 49), gait pattern (5 of 49) and muscle power (2 of 49). At ICF-CY level of activities and participation hand and arm use (9 of 49), fine hand use (5 of 49), lifting and carrying objects (3 of 49), maintaining a body position (2 of 49), walking (1 of 49) and moving around using equipment (1 of 49) was assessed. Only a few methods are potentially suitable outside the clinical environment (e.g. inertial sensors, accelerometers).

CONCLUSION

Although the current review shows the potential of several instrumented methods to be used as objective outcome measures in dyskinetic cerebral palsy, their methodological quality is still unknown. Future development should focus on evaluating clinimetrics, including validating against clinical meaningfulness. New technological developments should aim for measurements that can be applied outside the laboratory.

Architectural Changes in the Medial Gastrocnemius on Sonography after Nerve Ablation in Healthy Adults

Architectural changes in healthy muscle after denervation have not yet been reported. This study aimed to investigate architectural changes in the medial head of the gastrocnemius muscle (GCM) after aesthetic tibial nerve ablation in healthy adults using ultrasonography (US). The effects of tibial nerve ablation were verified by visual observation and surface electromyography analysis. US images of medial GCMs were taken by one trained physician using B-mode and real-time US with a linear-array probe before nerve ablation, at 1 week after nerve ablation and at 3 months after nerve ablation in an anatomic standing position with the feet about shoulder-width apart in 19 healthy adults (17 females and 2 males). Muscle thickness was significantly reduced on the left side at 1 week and 3 months after the procedure and on the right side at 3 months after the procedure (p<0.050). Although fascicle length was not significantly changed, pennation angle was significantly reduced on both sides at 3 months after the procedure (p<0.050). Muscle thickness and pennation angle of the muscle fascicle were significantly reduced, although fascicle length was not significantly changed, after tibial nerve ablation in the medial GCM of healthy adults.

A framework for closing the loop between human experts and computational algorithms for the assessment of movement disorders

Clinical assessment of abnormal neuromechanics is typically performed by manipulation of the affected limbs; a process with low inter- and intra-rater reliability. This paper aims at formalizing a framework that closes the loop between a clinician's expertise and computational algorithms, to enhance the clinician's diagnostic capabilities during physical manipulation. The framework's premise is that the dynamics that can be measured by manipulation of a limb are distinct between movement disorders. An a priori database contains measurements encoded in a space called the information map. Based on this map, a computational algorithm identifies which probing motions are more likely to yield distinguishing information about a patient's movement disorder. The clinician executes this movement and the resulting dynamics, combined with clinician input, is used by the algorithm to estimate which of the movement disorders in the database are most probable. This is recursively repeated until a diagnosis can be confidently made. The main contributions of this paper are the formalization of the framework and the addition of the information map to select informative movements. The establishment of the framework provides a foundation for a standardized assessment of movement disorders and future work will aim at testing the framework's efficacy.

Transition Between the Timed up and Go Turn to Sit Subtasks: Is Timing Everything?

OBJECTIVE

The Timed Up and Go (TUG), one of the most widely used tests of mobility, has been validated and associated with adverse outcomes in the community, acute care, and nursing home setting. It is composed of several distinct subtasks; however, the temporal relationship when transitioning between subtasks has not been well-studied. We tested the hypothesis that longer transition durations between the final turn to the sitting subtasks are associated with worse motor and cognitive performance in older adults.

METHODS

A total of 1055 participants (80.33 ± 7.57 years, 76.96% female) performed the TUG while wearing a 3-dimensional inertial sensor on their lower back. We employed a series of linear regressions to examine the association of the duration between the turn and sitting subtasks with clinical characteristics including motor and cognitive functions.

RESULTS

Participants employed 2 different strategies when they transitioned from turning to sitting. (1) Distinct transition strategy: 816 participants (77.34%) first completed the turn before starting to sit. The average duration between these distinct subtasks (D-interval) was 715 ± 980 ms. (2) Overlapping transition strategy: 239 participants (22.65%) started to sit before completing the turn. The average overlap duration between these tasks (O-interval) was 237 ± 269 ms. Participants who employed the distinct transition strategy were slightly younger than those who employed the overlapping transition strategy (P ≤ .013). Higher D-intervals and O-intervals were associated with worse TUG performance (P ≤ .02), with poorer motor and cognitive function, [ie, worse parkinsonian gait (P ≤ .001), lower level of perceptual speed (P ≤ .03), and with worse mobility disability (P ≤ .001)]. A longer D-interval was associated with worse gait speed and bradykinesia (P ≤ .001), whereas a longer O-interval was associated with increased rigidity (P = .004).

CONCLUSIONS

Older adults apparently employ 2 different strategies when transitioning from turning to sitting. The instrumented TUG can characterize additional gait and balance aspects that cannot be derived from traditional TUG assessments. These new measures offer novel targets for intervention to decrease the burden of late-life gait impairment.

Identification and measurement of dystonia in cerebral palsy

AIM

To establish the prevalence and severity of dystonia in a population of children with cerebral palsy (CP) with hypertonia assessment and measurement tools.

METHOD

A cross-sectional study of 151 children (84 males, 67 females) with CP who were assessed with the Hypertonia Assessment Tool (HAT) and Barry-Albright Dystonia scale (BAD) for identification and measurement of severity of dystonia. HAT dystonia items were assessed for construct and convergent validity.

RESULTS

Distribution by predominant motor type (PMT) was: 85% spastic, 14% dyskinetic, and 1% ataxic. Spastic and dyskinetic groups showed widespread evidence of dystonia according to HAT profiles and BAD scores. The dyskinetic PMT group had a higher mean BAD score than the spastic group (difference of 13 units, 95% CI 9.1-16.4). Dystonia severity (BAD score) increased linearly across gross motor (p<0.001), manual ability (p<0.001) and communication functional levels (p<0.001). Divergence was noted in how HAT item six identified dystonia compared to items one and two.

INTERPRETATION

The HAT provided an estimate of the prevalence of both spasticity and dystonia in a large CP population, beyond predominant motor type. Dystonia is a common finding in the spastic PMT group, and its severity increases as motor function worsens.

WHAT THIS PAPER ADDS

Dystonia is readily identified in cerebral palsy (CP) using the Hypertonia Assessment Tool, regardless of the predominant motor type. Spasticity and dystonia frequently coexist in the CP population. Severity of dystonia is inversely related to motor function.

Clinical Management of Dystonia in Childhood

Dystonia is one of the most frequent movement disorders in childhood. It can impede normal motor development and cause significant motor disability. The diagnostic evaluation of childhood dystonia is challenging due to the phenotypic variability and heterogeneous etiologies. Evidence to guide the diagnostic evaluation and treatment is limited. Assessment is primarily directed by clinical history and distinctive examination findings. Neuroimaging is typically necessary to evaluate for acquired or complex inherited dystonias. A trial of levodopa can be both diagnostic and therapeutic in children with dopa-responsive dystonia. However, for the majority of children with early-onset dystonia, treatment is symptomatic with varying efficacy. There is a paucity of therapeutic trials for childhood dystonia and most treatment recommendations are consensus or expert opinion driven. This review summarizes the available evidence and guidelines on the diagnostic evaluation and pharmacological treatment of childhood-onset dystonia and provides practical frameworks to approach both issues based on best evidence.

Upper Limb Function, Kinematic Analysis, and Dystonia Assessment in Children With Spastic Diplegic Cerebral Palsy and Periventricular Leukomalacia

Assessment of upper limb function, kinematic analysis, and dystonia in patients with spastic diplegia cerebral palsy and periventricular leukomalacia. Seven children with spastic diplegia cerebral palsy and 8 controls underwent upper limb kinematics. Movement duration, average and maximum linear velocity, index of curvature, index of dystonia, and target accuracy and stability were analyzed. In the patients with spastic diplegia, Gross Motor Function and Manual Ability Classification Systems were determined, and spasticity and dystonia were rated using the Modified Ashworth and the Burke-Fahn-Marsden Dystonia scales respectively. Children with spastic diplegia demonstrated a tendency toward higher index of dystonia reflecting overflow, higher index of curvature, lower velocities, and poor target accuracy and stability. All patients showed clinical evidence of dystonia in the upper limbs. Dystonia scores correlated with the Manual Ability Classification System (r = 0.86, P = .01) and with the index of dystonia (r = 0.82, P = .02). Children with spastic diplegia cerebral palsy present dystonia in the upper limbs. This is functionally relevant and can be measured with kinematic analysis.

An electromyographic protocol that distinguishes spasticity from dystonia

PURPOSE

The purpose of this proof of concept study is to demonstrate that electromyographic (EMG) activation patterns of leg muscles differ predictably among patients with predominantly spasticity, patients with predominantly dystonia, and typically developing control subjects during rest, volitional movement, and passively induced movement.

METHODS

Eight control subjects, 6 subjects with dystonia, and 7 subjects with spasticity were recruited, ages 6-25 years. Surface EMG sensors were applied over 4 muscle groups of each leg. EMG recordings and video were obtained during rest, quick stretch, and volitional movement. The number of muscles active during 3 resting, 4 quick stretch, and 8 volitional movement items were averaged and compared across subject groups.

RESULTS

Control subjects showed minimal numbers of muscles active during resting, quick stretch, or volitional movement activities. Spastic subjects showed multiple muscles responding with high amplitude to quick stretch but not to volitional movement activities. Dystonic subjects showed multiple muscles responding to volitional movement activities but not to quick stretch. Analysis with a Kruskal-Wallis test indicated significant differences between the three groups in numbers of muscles activated during quick stretch activities (p= 0.017) and volitional movement activities (p= 0.005).

CONCLUSION

EMG data collected with this protocol may be useful for distinguishing spastic from dystonic hypertonia.

Motor control investigation of dystonic cerebral palsy: A pilot study of passive knee trajectory

The purpose of this study is to better understand dystonia in CP and be able to objectively distinguish between individuals who experience spasticity, dystonia, or a combination of these conditions while evaluating the effect of 2Hz vestibular stimulation. Selected outcome measures included knee ROM, angular velocity and acceleration and all measures increased post vestibular stimulation; these results are indications of a possible reduction in the level of disability. The current investigation also identified an unexpected and unique behavior of the knee in children with dystonic cerebral palsy (CP) that was noticed while administering the Pendulum Knee Drop test (PKD) at approximately 0.4 rad (a mid-angle between full extension and zero vertical). There was a catch-like phenomenon at the described mid-angle in dystonic individuals. These results may suggest that dystonia is not a velocity dependent hypersensitivity of reflexes, but may include position dependent muscle reflexes and co-contractions. This reinforces the need for a more precise objective measure or perhaps a modified measure such as a mid-angle PKD test. Furthermore, based on the results obtained through the modified technique, beneficial alterations can be made to the form of treatment such as: robotic therapy or physical therapy that specifically accommodates the unique motor control disorder in individuals with dystonic CP.

Corporal diagnostic work and diagnostic spaces: clinicians' use of space and bodies during diagnosis

An emerging body of literature in sociology has demonstrated that diagnosis is a useful focal point for understanding the social dimensions of health and illness. This article contributes to this work by drawing attention to the relationship between diagnostic spaces and the way in which clinicians use their own bodies during the diagnostic process. As a case study, we draw upon fieldwork conducted with a multidisciplinary clinical team providing deep brain stimulation (DBS) to treat children with a movement disorder called dystonia. Interviews were conducted with team members and diagnostic examinations were observed. We illustrate that clinicians use communicative body work and verbal communication to transform a material terrain into diagnostic space, and we illustrate how this diagnostic space configures forms of embodied 'sensing-and-acting' within. We argue that a 'diagnosis' can be conceptualised as emerging from an interaction in which space, the clinician-body, and the patient-body (or body-part) mutually configure one another. By conceptualising diagnosis in this way, this article draws attention to the corporal bases of diagnostic power and counters Cartesian-like accounts of clinical work in which the patient-body is objectified by a disembodied medical discourse.

Increased long-latency reflex activity as a sufficient explanation for childhood hypertonic dystonia: a neuromorphic emulation study

OBJECTIVE

Childhood dystonia is a movement disorder that interferes with daily movements and can have a devastating effect on quality of life for children and their families. Although injury to basal ganglia is associated with dystonia, the neurophysiological mechanisms leading to the clinical manifestations of dystonia are not understood. Previous work suggested that long-latency stretch reflex (LLSR) is hyperactive in children with hypertonia due to secondary dystonia. We hypothesize that abnormal activity in motor cortices may cause an increase in the LLSR leading to hypertonia.

APPROACH

We modeled two possibilities of hyperactive LLSR by either creating a tonic involuntary drive to cortex, or increasing the synaptic gain in cortical neurons. Both models are emulated using programmable very-large-scale-integrated-circuit hardware to test their sufficiency for producing dystonic symptoms. The emulation includes a joint with two Hill-type muscles, realistic muscle spindles, and 2,304 Izhikevich-type spiking neurons. The muscles are regulated by a monosynaptic spinal pathway with 32 ms delay and a long-latency pathway with 64 ms loop-delay representing transcortical/supra-spinal connections.

MAIN RESULTS

When the limb is passively stretched, both models produce involuntary resistance with increased antagonist EMG responses similar to human data; also the muscle relaxation is delayed similar to human data. Both models predict reduced range of motion in voluntary movements.

SIGNIFICANCE

Although our model is a highly simplified and limited representation of reflex pathways, it shows that increased activity of the LLSR is by itself sufficient to cause many of the features of hypertonic dystonia.

Further evaluation of the scoring, reliability, and validity of the Hypertonia Assessment Tool (HAT)

We assessed the impact of videotape analysis on scoring of the Hypertonia Assessment Tool (HAT) that discriminates between hypertonia subtypes. The HAT was administered to 28 children with cerebral palsy (mean age 9 years, range 4-17 years, 61% male). HAT examinations were videotaped; scores were assigned before and after videotape review. Neurological examination provided the gold standard diagnosis. Interrater reliability, criterion validity and individual item validation were assessed using prevalence and bias-adjusted kappa (PABAK). Videotape review did not significantly change the HAT item scores or diagnoses. Item validation eliminated 1 dystonia item. Interrater reliability was moderate for dystonia (PABAK = 0.43) and excellent for spasticity and rigidity (PABAK = 0.86-1.0). Criterion validity was substantial for spasticity (PABAK = 0.71), moderate for dystonia (PABAK = 0.43-0.57) and excellent for the absence of rigidity (PABAK = 1.0). The HAT can be administered without videotape review. Dystonia item 1 did not change the HAT hypertonia diagnosis and will be removed from the HAT.

Dystonia in childhood: clinical and objective measures and functional implications

Dystonia is a complex movement disorder that is challenging to identify and quantify. The aim of this article is to review the clinical scales, kinematic measures, and functional implications of dystonia. Clinical measures include the Barry-Albright Dystonia Scale, the Burke-Fahn-Marsden Movement Scale, the Unified Dystonia Rating Scale, the Global Dystonia Rating Scale, and the Movement Disorder-Childhood Rating Scale. The evidence, reliability, and validity of each scale will be outlined. The Hypertonia Assessment Tool will be discussed emphasizing the importance of discriminating hypertonia. The role of kinematic measures in analyzing dystonia will be explored, as well as the potential for its future clinical applications.

In vivo evaluations of morphologic changes of gastrocnemius muscle fascicles and achilles tendon in children with cerebral palsy

OBJECTIVE

The Achilles tendon plays an important role in soleus and gastrocnemius muscle functions, including proper muscle force transmission and movement generation. However, few studies have examined concurrent changes of tendon and muscle properties in neurologic disorders. The objective of this study was to investigate the morphologic characteristics of both the calf muscle fascicles and the Achilles tendon in children with cerebral palsy (CP).

DESIGN

A cross-sectional study was planned, and 12 children with CP and 11 typically developing children participated in this study. For both groups, B-mode ultrasonography was used to evaluate the architecture of the medial gastrocnemius muscle, including fascicle length and pennation angle at various ankle (20, 10, and 0 degrees plantar flexion and 10 degrees dorsiflexion) and knee (full extension and 90 degrees flexion) positions. The length and cross-sectional area of the Achilles tendon were also evaluated using ultrasonography.

RESULTS

For both CP and control groups, muscle fascicle length, pennation angle, and Achilles tendon length and cross-sectional area varied with ankle and knee positions systematically. Compared with controls, children with CP had shorter muscle fascicles across the tested ankle range of motion (P ≤ 0.003), longer Achilles tendon (P = 0.001), and smaller cross-sectional area of the Achilles tendon (P = 0.003).

CONCLUSIONS

The changes in Achilles tendon properties could be a result of adaptation to calf muscle fascicle shortening and stiffening, which may affect performance of the muscles. A better understanding of the interactions between calf muscle fascicles and Achilles tendon in children with CP may help treat the pathologic changes more effectively.

Reaching and writing movements: sensitive and reliable tools to measure genetic dystonia in children

The aim of this study was to provide a quantitative assessment of pure dystonia in a group of children. Kinematic and muscular characteristics of unconstrained movements of the upper limb, reaching and writing, were investigated. During reaching, the distinguishing factors of dystonic movement were reduced velocity, loss of muscular activation focalization, and impairment of rest-movement modulation. Muscular parameters were able to linearly discriminate the different levels of severity. These results support the hypothesis that basal ganglia dysfunction is responsible for compromising the motor activity focusing. The handwriting movement revealed that the kinematic coordination was altered depending on dystonia severity scores. The 2 protocols revealed themselves feasible and sensitive for detecting even local and subclinical signs. Hence, this work provides a contribution toward a reliable assessment of pure dystonia, crucial for clinical characterization of patients and evaluation of the different treatment options.

Finger muscle control in children with dystonia

BACKGROUND

Childhood dystonia is a disorder that involves inappropriate muscle activation during attempts at voluntary movement. Few studies have investigated the muscle activity associated with dystonia in children, and none have done so in the hands.

METHODS

In this study, we measured surface electromyographic activity in four intrinsic hand muscles while participants attempted to perform an isometric tracking task using one of the muscles.

RESULTS

Children with dystonia had greater tracking error with the task-related muscle and greater overflow to non-task muscles. Both tracking error and overflow correlated with the Barry-Albright Dystonia scale of the respective upper limb. Overflow also decreased when participants received visual feedback of non-task muscle activity.

DISCUSSION

We conclude that two of the motor deficits in childhood dystonia--motor overflow and difficulties in actively controlling muscles--can be seen in the surface electromyographic activity of individual muscles during an isometric task. As expected from results in adults, overflow is an important feature of childhood dystonia. However, overflow may be at least partially dependent on an individual's level of awareness of their muscle activity. Most importantly, poor single-muscle tracking shows that children with dystonia have deficits of individual muscle control in addition to overflow or co-contraction. These results provide the first quantitative measures of the muscle activity associated with hand dystonia in children, and they suggest possible directions for control of dystonic symptoms.

Contributors to excess antagonist activity during movement in children with secondary dystonia due to cerebral palsy

Children with secondary dystonia due to cerebral palsy exhibit abnormal upper extremity postures and slow voluntary movement. However, the interaction between abnormal postures and abnormal movement in dystonia is still unclear. Some mechanisms by which postures are maintained in dystonia include stretch reflexes, overflow of muscle activation to other muscles, and direct coactivation of antagonist muscles. This study explored the independent contributions of each of these postural mechanisms to abnormal biceps brachii (antagonist) activity during elbow extension, which slows movement. A linear model of biceps activation as a function of velocity-dependent reflexes, triceps-dependent overflow, and direct drive to the biceps was fitted to experimental data from 11 children and young adults with secondary dystonia due to cerebral palsy and 11 age-matched control subjects. Subjects performed elbow extension movements against each of four levels of resistance without perturbations or in each of two perturbation conditions. Results show that biceps activity in children with dystonia consists of significant contributions of reflex activation, overflow from triceps, and direct muscular drive. Additionally, stretch reflexes during movement are shown to be elevated at three latencies after stretch. These findings suggest that there are postural mechanisms involved in stabilizing the elbow along its slow trajectory during movement and provide a quantitative basis for the selection of treatments targeting specific impairments in children with secondary dystonia due to cerebral palsy.

Visual feedback reduces co-contraction in children with dystonia

Inappropriate muscle activation and co-contraction are important features in childhood dystonia, and clinical interventions are often targeted to reduce the excess muscle activation. Previous research has shown that visual biofeedback of muscle activity can help people to reduce excess muscle activation in a variety of motor disorders. To investigate the effectiveness of similar techniques for dystonia, we had participants perform a tracking task with and without visual feedback of co-contraction. Children with dystonia had greater levels of co-contraction than children without dystonia. Most importantly, individuals were able to reduce their co-contraction significantly when visual biofeedback was provided. These results indicate that children with dystonia are able to control co-contraction, at least to a certain extent, provided attention can be directed to the excess muscle activation. These results also suggest that methods of biofeedback focusing on inappropriate muscle activations might provide a clinical benefit for treatment of children with dystonia.

Electromyographic (EMG) analysis of quadriceps muscle fatigue in children with cerebral palsy during a sustained isometric contraction

The purpose of this investigation was to determine whether changes in surface electromyography (EMG) data during an isometric muscle protocol, in combination with maximal voluntary isometric force, provide information on fatigue occurrence and exercise limitation in children with cerebral palsy. Twelve children with cerebral palsy and 10 age-matched controls completed an assessment of quadriceps muscle fatigue on an isokinetic device with surface EMG measurements, during a sustained isometric contraction at 50% of the maximal voluntary isometric force. The EMG data collected in participants with cerebral palsy suggest that muscle fatigue occurred sooner in children with cerebral palsy relative to the age-matched controls. However, the results demonstrate that no difference was found in time to exhaustion between the able-bodied and participants with cerebral palsy. These contrasting results may be the result of spasticity and co-contraction during maximal testing, which may play an important role in exercise limitation in children with cerebral palsy.

Hypertonia in childhood secondary dystonia due to cerebral palsy is associated with reflex muscle activation

It is often assumed that co-contraction of antagonist muscles is responsible for increased resistance to passive movement in hypertonic dystonia. Although co-contraction may certainly contribute to hypertonia in some patients, the role of reflex activation has never been investigated. We measured joint torque and surface electromyographic activity during passive flexion and extension movements of the elbow in 8 children with hypertonic arm dystonia due to dyskinetic cerebral palsy. In all cases, we found significant phasic electromyographic activity in the lengthening muscle, consistent with reflex activity. By correlating activation with position or velocity of the limb, we determined that some children exhibit position-dependent activation, some exhibit velocity-dependent activation, and some exhibit a mixed pattern of activation. We conclude that involuntary or reflex muscle activation in response to stretch may be a significant contributor to increased tone in hypertonic dystonia, and we conjecture that this activation may be more important than co-contraction for determining the resistance to passive movement.

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.

Pre- and postsurgical evaluation of hand function in hemiplegic cerebral palsy: exemplar cases

Evaluation of hand function for treatment planning and outcome documentation in individuals with cerebral palsy (CP) proves challenging. Because of the complexity of multisystem involvement and time constraints during physician clinic visits, we developed a comprehensive evaluation protocol to assist with team surgical decision making in CP. We report findings from three adolescents with hemiplegic CP who were evaluated pre-/post-intervention using measures of impairment (clinical examination procedures), activity (Pediatric Evaluation of Disability Inventory and Jebsen-Taylor Test of Hand Function), and participation (goal attainment scaling). An intervention to improve hand function consisted of single-event multilevel orthopedic surgery and postsurgical therapy. Wrist/finger biomechanics and active range of motion improved after the intervention. The targeted surgical intervention and undefined therapy intervention, however, seemed to have little influence on activity and participation. The descriptive results of these exemplar cases suggest that, instead of assisting only with surgical decision making, the evaluation protocol should focus on specific postsurgical therapy plans in addition to surgical/therapy decision making.

Clinical factors that affect walking level and performance in chronic spinal cord lesion patients

STUDY DESIGN

Observational Study.

OBJECTIVE

To evaluate the effects of neurologic and non-neurologic factors on walking level and performance in chronic spinal cord lesion (SCL) patients.

SUMMARY OF BACKGROUND DATA

Walking is one of the primary goals of patients after a SCL. Several studies have demonstrated that different neurologic and non-neurologic factors can affect walking level and performance. However, in SCL age and muscle strength have always been considered the major determinants of walking.

METHODS

Sixty-five patients with chronic SCL were included. Their demographic, neurologic status (ASIA standards), balance, and spasticity were recorded. Pearson and Spearman correlations were adopted to quantify the association between patients' characteristics and walking ability. The relationship between functional walking measures, Timed Up and Go, Six Minutes Walking Test (SMWT), Ten Meters Walking Test, and Walking Index for Spinal Cord Injury, and demographic and neurologic factors were measured by regression analyses.

RESULTS

Strength, balance, spasticity, and age were strictly correlated with walking level and walking performance. They also were the best predictors of walking features.

CONCLUSION

Results confirm the recognized importance of age and upper and lower extremity strengths for walking after a SCL. They also highlight the role of 2 other factors, i.e., balance and spasticity, seldom considered as thoroughly in SCL.

Can spasticity and dystonia be independently measured in cerebral palsy?

Selecting and evaluating appropriate treatments for children with cerebral palsy has been challenging. One difficulty is in the ability to quantify the presence and importance of coexisting motor signs. This study presents quantitative measures developed to assess spasticity and dystonia. Children diagnosed with extrapyramidal or spastic cerebral palsy and matched control children were studied. Spasticity was measured as the slope of the force-velocity relationship from a test where we measured the forces required to passively extend the elbow at different velocities. Dystonia was assessed by measuring "overflow" movements of arm during active movement of the other arm. Measures of dystonia and spasticity did not correlate with one another, but did correlate with their respective clinical measurement tools, the Modified Ashworth scale and the Barry-Albright Dystonia scale. Most children had a combination of both spasticity and dystonia, despite diagnosis. Our measures also related to different aspects of reaching: children with increased dystonia made more curved paths, and children with increased spasticity hit higher peak velocities. These measurements allow us to distinguish between different motor disorders and the degree to which each contributes to reaching performance. Use of quantitative measures should improve selection and evaluation of treatments for childhood motor disorders.

Definition and classification of negative motor signs in childhood

In this report we describe the outcome of a consensus meeting that occurred at the National Institutes of Health in Bethesda, Maryland, March 12 through 14, 2005. The meeting brought together 39 specialists from multiple clinical and research disciplines including developmental pediatrics, neurology, neurosurgery, orthopedic surgery, physical therapy, occupational therapy, physical medicine and rehabilitation, neurophysiology, muscle physiology, motor control, and biomechanics. The purpose of the meeting was to establish terminology and definitions for 4 aspects of motor disorders that occur in children: weakness, reduced selective motor control, ataxia, and deficits of praxis. The purpose of the definitions is to assist communication between clinicians, select homogeneous groups of children for clinical research trials, facilitate the development of rating scales to assess improvement or deterioration with time, and eventually to better match individual children with specific therapies. "Weakness" is defined as the inability to generate normal voluntary force in a muscle or normal voluntary torque about a joint. "Reduced selective motor control" is defined as the impaired ability to isolate the activation of muscles in a selected pattern in response to demands of a voluntary posture or movement. "Ataxia" is defined as an inability to generate a normal or expected voluntary movement trajectory that cannot be attributed to weakness or involuntary muscle activity about the affected joints. "Apraxia" is defined as an impairment in the ability to accomplish previously learned and performed complex motor actions that is not explained by ataxia, reduced selective motor control, weakness, or involuntary motor activity. "Developmental dyspraxia" is defined as a failure to have ever acquired the ability to perform age-appropriate complex motor actions that is not explained by the presence of inadequate demonstration or practice, ataxia, reduced selective motor control, weakness, or involuntary motor activity.

Pharmacotherapy of spasticity in children with cerebral palsy

Spasticity is one of the most common symptoms presented by neurologic patients. Apart from surgical management, drug therapy is an important treatment of children suffering from spasticity. In this review, recent advances in the pharmacologic armamentarium are reported in detail. In particular, there are oral medications (benzodiazepines, baclofen, dantrolene sodium, alpha 2 adrenergic agonists) and parenteral medications (botulinum toxin type A and B, alcohol). Moreover, there is also baclofen that can be administered intrathecally. There are some reports supporting the use of intramuscular alcohol (45% and/or 5-7% phenol) to reduce spasticity without the loss of voluntary movement or loss of sensation. Among these drugs, intrathecal baclofen is one of the most effective substances that can reduce spasticity significantly in the upper and lower extremities. Finally, the effectiveness of therapy with botulinum toxin type A in the management of spasticity is analyzed. Botulinum toxin type A reduces hypertonia in the injected muscles for a period of 2 to 4 months without important side effects. The purpose of this article is to provide an overview of available oral and parenteral drugs for treatment of spasticity in cerebral palsy and to outline indications and contraindications.

Toward a definition of childhood dystonia

PURPOSE OF REVIEW

The purpose of this review is to summarize recent progress toward providing a consistent, sensitive, specific, and useful definition of dystonia as it presents in childhood.

RECENT FINDINGS

An NIH-funded consensus group published a definition of childhood dystonia in January of 2003. Recent work has attempted to identify quantitative methods for diagnosis and measurement of childhood dystonia. Techniques include biomechanical, kinematic, and surface EMG measurements that show promise for providing specific and sensitive measures of childhood dystonia.

SUMMARY

The results of current research efforts will be useful for verifying and modifying definitions of dystonia to provide consistent and measurable terms for including children in research trials and selecting appropriate interventions for clinical treatment.