Yannick Bleyenheuft

Corticospinal dysgenesis and upper-limb deficits in congenital hemiplegia : a diffusion tensor imaging study

OBJECTIVES. Precision grasping critically relies on the integrity of the corticospinal tract as evidenced in congenital hemiplegia by the correlation found between corticospinal dysgenesis and hand-movement deficits. Therefore, corticospinal dysgenesis could be used to anticipate upper-limb deficits in young infants with congenital hemiplegia. However, most studies have quantified corticospinal dysgenesis by measuring the cross-sectional area of cerebral peduncles on T1 MRI, a measure biased by other structures present in the peduncles. The purpose of this study was to evaluate the extent to which this may have hampered the conclusions of previous studies. We also aimed to investigate the relationship between upper-limb deficits and a more accurate measure of corticospinal dysgenesis to provide a tool for anticipating upper-limb deficits in infants with congenital hemiplegia. METHODS. To address this issue, we measured corticospinal tract areas in 12 patients with congenital hemiplegia and 12 matched control subjects by using the diffusion tensor imaging technique. Corticospinal dysgenesis was quantified by computing a symmetry index between the area of the contralateral and ipsilateral corticospinal tracts. This value was then compared with that resulting from the conventional MRI method. RESULTS. The symmetry indexes gathered with these 2 methods were highly correlated, although the diffusion tensor imaging symmetry indexes were significantly smaller. This indicates that, in patients with congenital hemiplegia, the conventional MRI measurement has led to a systematic underestimate of corticospinal dysgenesis. These 2 estimates of corticospinal dysgenesis were also correlated with upper-limb impairments and disabilities. Although the symmetry index computed from peduncle measurements was correlated solely with deficits in stereognosis, the diffusion tensor imaging index correlated with stereognosis, digital and manual dexterities, and ABILHAND-Kids, a measure of manual ability in daily life activities. CONCLUSIONS. The diffusion tensor imaging symmetry index provides a useful prognostic tool for anticipating upper-limb deficits and their consequences in daily life activities.

Hand Functioning in Children with Cerebral Palsy

Brain lesions may disturb hand functioning in children with cerebral palsy (CP), making it difficult or even impossible for them to perform several manual activities. Most conventional treatments for hand dysfunction in CP assume that reducing the hand dysfunctions will improve the capacity to manage activities (i.e., manual ability, MA). The aim of this study was to investigate the directional relationships (direct and indirect pathways) through which hand skills influence MA in children with CP. A total of 136 children with CP (mean age: 10 years; range: 6–16 years; 35 quadriplegics, 24 diplegics, 77 hemiplegics) were assessed. Six hand skills were measured on both hands: touch-pressure detection (Semmes–Weinstein esthesiometer), stereognosis (Manual Form Perception Test), proprioception (passive mobilization of the metacarpophalangeal joints), grip strength (GS) (Jamar dynamometer), gross manual dexterity (GMD) (Box and Block Test), and fine finger dexterity (Purdue Pegboard Test). MA was measured with the ABILHAND-Kids questionnaire. Correlation coefficients were used to determine the linear associations between observed variables. A path analysis of structural equation modeling was applied to test different models of causal relationships among the observed variables. Purely sensory impairments did seem not to play a significant role in the capacity to perform manual activities. According to path analysis, GMD in both hands and stereognosis in the dominant hand were directly related to MA, whereas GS was indirectly related to MA through its relationship with GMD. However, one-third of the variance in MA measures could not be explained by hand skills. It can be concluded that MA is not simply the integration of hand skills in daily activities and should be treated per se, supporting activity-based interventions.

Treatment of genu recurvatum in hemiparetic adult patients: A systematic literature review

INTRODUCTION AND METHODS We carried out a systematic review of the literature on treatment of genu recurvatum in hemiparetic adult patients by searching the PubMed, Pedro, Trip Database and Science Direct databases. The following keywords were used: (recurvatum or hyperextension or knee) and (hemiplegia or hemiparesis). RESULTS Nine articles met our selection criteria. Four assessed retraining methods (functional electric stimulation or electrogoniometric feedback), two assessed orthopaedic or neurosurgical treatments and three articles focused on orthoses. DISCUSSION AND CONCLUSION Even though all the various treatments produced encouraging results, most of the reviewed studies presented methodological limitations. Moreover, none of the selected articles suggested a treatment strategy which takes account of the various aetiologies in genu recurvatum. On the basis of some of the reviewed articles and our own clinical experience, we propose an aetiology-specific treatment strategy for genu recurvatum patients. In a broad patient population, this categorization could form the basis for testing the specificity of each treatment method as a function of the cause of genu recurvatum. This approach could help confirm the clinical indications and identify the most appropriate treatment for each patient.

Pathophysiology of impaired hand function in children with unilateral cerebral palsy.

Unilateral spastic cerebral palsy, caused by damage to the developing central nervous system, is characterized by motor impairments mainly lateralized to one side of the body, with hand impairments greatly contributing to functional limitations. The integrity of the motor areas and the corticospinal tract (CST) is often compromised. The specific etiology may drastically influence subsequent development of CST pathways. Here we describe the pathophysiology underlying impaired upper extremity function, with particular emphasis on the relation between CST damage and hand function. We also describe the resulting sensory and motor deficits, with an emphasis on studies of precision grip, which highlight impairments in motor execution, sensorimotor integration, motor planning, and bimanual coordination beyond dexterity impairments. We show that the type and extent of early brain damage and/or CST reorganization is highly predictive of the severity of these impairments. We discuss the clinical implications of these findings, including the intriguing possibility that the specific pathophysiology is predictive of treatment outcomes. We suggest that a ‘one‐treatment fits all approach’ may be insufficient, and that future rehabilitation efforts will be best guided by closely relating treatment efficacy with the specific pathophysiology.

Tactile spatial resolution measured manually: a validation study.

The purpose of this study was to investigate the validity of manual application of the grating orientation task (GOT), as currently used in fundamental and clinical research. Six examiners tested 12 subjects following recommendations of the literature. The results show that the normal force applied with the domes on the skin varied from one examiner to the next. Nevertheless, it did not affect the performance of the subjects, whose thresholds were consistent with those reported in the literature. This study highlights the inter-examiner reliability in the manual application of this test and validates this procedure.

Hand and Arm Bimanual Intensive Therapy Including Lower Extremity (HABIT-ILE) in Children With Unilateral Spastic Cerebral Palsy: A Randomized Trial.

Background. Intensive bimanual training results in more improvement in hand function in children with unilateral spastic cerebral palsy (USCP) than lower intensity conventional interventions. However, it is not known whether combined upper and lower extremity training in an intensive protocol is more efficacious for upper and lower functional abilities than conventional therapies provided in usual customary care. Objective. To determine the efficacy of Hand and Arm Bimanual Intensive Therapy Including Lower Extremity (HABIT-ILE) for children with USCP. Methods. Twenty-four children with USCP were randomized into 2 groups: an immediate HABIT-ILE group (IHG, initially receiving HABIT-ILE, 10 days = 90 hours), and a delayed HABIT-ILE group (DHG), which continued their conventional/ongoing treatment for an intended total duration of 90 hours. In phase 2, children in the DHG were crossed over to receive HABIT-ILE and children of the IHG were followed in their ongoing conventional therapy. Children were assessed using the Assisting Hand Assessment (AHA, primary outcome), the ABILHAND-Kids, and the Pediatric Evaluation of Disability Inventory. Dexterity (Box and Blocks Test [BBT]) and pinch strength were also measured. Locomotor abilities were assessed with Six-Minute Walk Test (6MWT, primary outcome) and ABILOCO-kids. Social participation was measured with the Assessment of Life-HABITs. Results. A 2 (groups) × 3 (test sessions) analysis of variance indicated significant improvements for primary outcomes (AHA, P < .001; 6MWT, P = .002) and all secondary assessments except BBT, step length and bodyweight distribution following HABIT-ILE, but not conventional therapy. Conclusion. The findings suggest that combined upper and lower extremity in an intensive training protocol may be efficacious for improving both upper and lower extremity function in children with USCP.

Altered gravity highlights Central Pattern Generator mechanisms

In many nonprimate species, rhythmic patterns of activity such as locomotion or respiration are generated by neural networks at the spinal level. These neural networks are called central pattern generators (CPGs). Under normal gravitational conditions, the energy efficiency and the robustness of human rhythmic movements are due to the ability of CPGs to drive the system at a pace close to its resonant frequency. This property can be compared with oscillators running at resonant frequency, for which the energy is optimally exchanged with the environment. However, the ability of the CPG to adapt the frequency of rhythmic movements to new gravitational conditions has never been studied. We show here that the frequency of a rhythmic movement of the upper limb is systematically influenced by the different gravitational conditions created in parabolic flight. The period of the arm movement is shortened with increasing gravity levels. In weightlessness, however, the period is more dependent on instructions given to the participants, suggesting a decreased influence of resonant frequency. Our results are in agreement with a computational model of a CPG coupled to a simple pendulum under the control of gravity. We demonstrate that the innate modulation of rhythmic movements by CPGs is highly flexible across gravitational contexts. This further supports the involvement of CPG mechanisms in the achievement of efficient rhythmic arm movements. Our contribution is of major interest for the study of human rhythmic activities, both in a normal Earth environment and during microgravity conditions in space.

Precision grip control, sensory impairments and their interactions in children with hemiplegic cerebral palsy: A systematic review §

Children with hemiplegic cerebral palsy (HCP) exhibit long-term functional deficits. One of the most debilitating is the loss of prehension since this may impair functional independence. This loss of prehension could be partly due to sensory deficits. Identifying the underlying causes of prehension deficits and their potential link with sensory disorders is important to better adapt neurorehabilitation. Here we provide an overview of precision grip and sensory impairments in individuals with HCP, and the relation between them, in order to determine whether the sensory impairments influence the type and magnitude of deficits as measured by studies of prehensile force control. Pubmed and Scopus databases were used to search studies from 1990 to 2012, using combinations of the following keywords: fingertip force; grip force; precision grip; sensory deficit; sensory impairment; tactile discrimination; with cerebral palsy. Of the 190 studies detected through the systematic search; 38 were finally included in the systematic part of this review. This review shows that sensory deficits are common and are likely underestimated using standard clinical assessments in HCP. Some studies suggest these deficits are the basis of predictive motor control impairments in these individuals. However, children with HCP retain some ability to use predictive control, even if it is impaired in the more affected hand. Intensive practice and initial use of the less affected hand, which has only subtle sensory deficits, has been shown to remediate impairments in anticipatory motor control during subsequent use of the more affected hand. Implications for motor and sensory rehabilitation of individuals with HCP are discussed.

Skilled Bimanual Training Drives Motor Cortex Plasticity in Children With Unilateral Cerebral Palsy.

Background. Intensive bimanual therapy can improve hand function in children with unilateral spastic cerebral palsy (USCP). We compared the effects of structured bimanual skill training versus unstructured bimanual practice on motor outcomes and motor map plasticity in children with USCP. Objective. We hypothesized that structured skill training would produce greater motor map plasticity than unstructured practice. Methods. Twenty children with USCP (average age 9.5; 12 males) received therapy in a day camp setting, 6 h/day, 5 days/week, for 3 weeks. In structured skill training (n = 10), children performed progressively more difficult movements and practiced functional goals. In unstructured practice (n = 10), children engaged in bimanual activities but did not practice skillful movements or functional goals. We used the Assisting Hand Assessment (AHA), Jebsen-Taylor Test of Hand Function (JTTHF), and Canadian Occupational Performance Measure (COPM) to measure hand function. We used single-pulse transcranial magnetic stimulation to map the representation of first dorsal interosseous and flexor carpi radialis muscles bilaterally. Results. Both groups showed significant improvements in bimanual hand use (AHA; P < .05) and hand dexterity (JTTHF; P < .001). However, only the structured skill group showed increases in the size of the affected hand motor map and amplitudes of motor evoked potentials (P < .01). Most children who showed the most functional improvements (COPM) had the largest changes in map size. Conclusions. These findings uncover a dichotomy of plasticity: the unstructured practice group improved hand function but did not show changes in motor maps. Skill training is important for driving motor cortex plasticity in children with USCP.

Age-related changes in tactile spatial resolution from 6 to 16 years old.

The aim of this study was to determine age-related changes in tactile spatial resolution from 6 to 16 years old. Two hundred and twenty-two healthy children (105 boys and 117 girls) were assessed. The tactile spatial resolution threshold was determined using a classic set of JVP domes with a procedure adapted for children. Preadolescence appears to be an important step in tactile spatial resolution since children aged between 6 and 9 years old had a worse tactile spatial resolution than older children. Both peripheral and central explanations for this improvement of tactile spatial resolution with age are considered. The authors suggest that cortical maturational processes are likely to explain the better results of older children.