Stroke in the Developing Brain: Neurophysiologic Implications of Stroke Timing, Location, and Comorbid Factors.

BACKGROUND: Pediatric stroke, which is unique in that it represents a static insult to a developing brain, often leads to long-term neurological disability. Neuroplasticity in infants and children influences neurophysiologic recovery patterns after stroke; therefore outcomes depend on several factors including the timing and location of stroke and the presence of comorbid conditions. METHODS: In this review, we discuss the unique implications of stroke occurring in the fetal, perinatal, and childhood/adolescent time periods. First, we highlight the impact of the developmental stage of the brain at the time of insult on the motor, sensory, cognitive, speech, and behavioral domains. Next, we consider the influence of location of stroke on the presence and severity of motor and nonmotor outcomes. Finally, we discuss the impact of associated conditions on long-term outcomes and risk for stroke recurrence. RESULTS: Hemiparesis is common after stroke at any age, although the severity of impairment differs by age group. Risk of epilepsy is elevated in all age groups compared with those without stroke. Outcomes in other domains vary by age, although several studies suggest worse cognitive outcomes when stroke occurs in early childhood compared with fetal and later childhood epochs. Conditions such as congenital heart disease, sickle cell disease, and moyamoya increase the risk of stroke and leave patients differentially vulnerable to neurodevelopmental delay, stroke recurrence, silent infarcts, and cognitive impairment. CONCLUSIONS: A comprehensive understanding of the interplay of various factors is essential in guiding the clinical care of patients with pediatric stroke.

A novel video game for remote studies of motor adaptation in children.

Here we designed a motor adaptation video game that could be played remotely (at home) through a web browser. This required the child to adapt to a visuomotor rotation between their hand movement and a ball displayed in the game. The task had several novel features, specifically designed to allow the study of the developmental trajectory of adaptation across a wide range of ages. We test the concurrent validity by comparing children's performance on our remote task to the same task performed in the laboratory. All participants remained engaged and completed the task. We quantified feedforward and feedback control during this task. Feedforward control, a key measure of adaptation, was similar at home and in the laboratory. All children could successfully use feedback control to guide the ball to a target. Traditionally, motor learning studies are performed in a laboratory to obtain high quality kinematic data. However, here we demonstrate concurrent validity of kinematic behavior when conducted at home. Our online platform provides the flexibility and ease of collecting data that will enable future studies with large sample sizes, longitudinal experiments, and the study of children with rare diseases.

Between Limb Muscle Co-activation Patterns in the Paretic Arm During Non-paretic Arm Tasks in Hemiparetic Cerebral Palsy.

Tasks of daily life require the independent use of the arms and hands. Individuals with hemiparetic cerebral palsy (HCP) often experience difficulty with fine motor tasks demonstrating mirrored movements between the arms. In this study, bilateral muscle activations were quantified during single arm isometric maximum efforts and submaximal reaching tasks. The magnitude and direction of mirrored activation was examined in 14 individuals with HCP and 9 age-matched controls. Participants generated maximum voluntary torques (MVTs) in five different directions and completed ballistic reaches while producing up to 80% of shoulder abduction MVT. Electromyography (EMG) signals were recorded from six upper extremity muscles bilaterally. Participants with HCP demonstrated more mirrored activation when volitionally contracting the non-paretic (NP) arm than the paretic arm (F = 83.543, p < 0.001) in isometric efforts. Increased EMG activation during reach acceleration resulted in a larger increase in rest arm co-activation when reaching with the NP arm compared to the paretic arm in the HCP group (t = 8.425, p < 0.001). Mirrored activation is more pronounced when driving the NP arm and scales with effort level. This directionality of mirroring is indicative of the use of ipsilaterally terminating projections of the corticospinal tract (CST) originating in the non-lesioned hemisphere. Peripheral measures of muscle activation provide insight into the descending pathways available for control of the upper extremity after early unilateral brain injury.

The Upper Extremity Flexion Synergy Is Minimally Expressed in Young Individuals With Unilateral Cerebral Palsy Following an Early Brain Injury.

Hemiparetic stroke in adulthood often results in the grouped movement pattern of the upper extremity flexion synergy thought to arise from an increased reliance on cortico-reticulospinal pathways due to a loss of lateral corticospinal projections. It is well established that the flexion synergy induces reaching constraints in individuals with adult-onset hemiplegia. The expression of the flexion synergy in individuals with brain injuries onset earlier in the lifespan is currently unknown. An early unilateral brain injury occurring prior to six months post full-term may preserve corticospinal projections which can be used for independent joint control and thus minimizing the expression of the flexion synergy. This study uses kinematics of a ballistic reaching task to evaluate the expression of the flexion synergy in individuals with pediatric hemiplegia (PH) ages six to seventeen years. Fifteen individuals with brain injuries before birth (n = 8) and around full-term (n = 7) and nine age-matched controls with no known neurological impairment completed a set of reaches in an admittance controlled robotic device. Descending drive, and the possible expression of the upper extremity flexion synergy, was modulated by increasing shoulder abduction loading. Individuals with early-onset PH achieved lower peak velocities when reaching with the paretic arm compared to controls; however, no differences in reaching distance were found between groups. Relative maintenance in reaching seen in individuals with early brain injuries highlights minimal expression of the flexion synergy. We interpret this conservation of independent control of the paretic shoulder and elbow as the use of more direct corticospinal projections instead of indirect cortico-reticulospinal pathways used in individuals with adult-onset hemiplegia.

Estimating Voluntary Activation Of The Elbow And Wrist Muscles In Chronic Hemiparetic Stroke Using Twitch Interpolation Methodology.

One of the cardinal motor deficits that occurs after stroke is paresis, a decrease in the voluntary activation of muscles. Paresis leads to a decrease in voluntary joint strength, impacting stroke survivors' ability to perform activities of daily living (ADLs). Quantifying this decrease in voluntary activation is important when designing rehabilitation interventions to address movement impairments and restore the ability to perform ADLs. Twitch interpolation is an experimental technique developed to quantify muscle voluntary activation [1]. This method has been used widely across pathologies but often limited to assessment of the voluntary activation of the plantar flexors, given the ease of activating these muscles through stimulation of the tibial nerve [2]. The complex innervation of elbow and wrist musculature imposes practical difficulties when applying the twitch interpolation technique to these joints [1]. Therefore, only a few studies have used this technique to examine the pathological [3]-[5] upper extremity, with little quantitative data documenting the degree of paresis present in the upper limb after stroke. The goal of this study is to evaluate the feasibility of applying twitch interpolation to quantify voluntary activation of the elbow and wrist flexors and extensors in chronic stroke survivors.

Development of a Method to Quantify Abnormal Kinetic and Kinematic Coupling Patterns during Functional Movements in the Paretic Arm and Hand of Individuals with Pediatric Hemiplegia.

A main focus of clinical interventions for adults after a stroke and children with hemiplegia is upper limb motor impairments. Robotic and motion capture technologies have been used to quantify the presence of abnormal joint coupling patterns in the arm and hand in adults who have had a stroke. Similar impairments have been observed clinically in children with hemiplegia, however, quantitative measurement tools tailored for this population are lacking. Here, we describe the integration of haptic robotics, pressure recording, and motion capture designed specifically for use with pediatric participants. Preliminary results demonstrate that these measurement techniques are effective in quantifying deficits in reaching abilities in this population.