F. Frascarelli

Working memory and mental imagery in cerebral palsy: a single case investigation.

In this study we describe visuospatial working memory and visual mental imagery of a child with Cerebral Palsy. Beyond a moderate impairment of visuomotor integration skills, cognitive level and memory span, poor performance emerged in figures reconstruction, in memorizing matrix patterns and movements along a path. No such deficits were observed in recalling figures and their positions on a grid and learning groups of words using a visual imagery strategy. This case highlights that impaired action execution impairs performance in imagery tasks as well, but not when alternative strategies (e.g., verbal encoding) can be adopted. Results are discussed considering recent evidence on working memory and visual imagery links, and their role in motor rehabilitation training.

Reach-to-grasp interjoint coordination for moving objects in children with hemiplegia

OBJECTIVE To evaluate interjoint coordination in children with hemiplegia as they reach to grasp objects, in both static and dynamic conditions. An ad hoc robotic device was used to study the dynamic condition. DESIGN Observational study. PATIENTS Six children with hemiplegia and 6 young adults. METHODS Kinematics of the trunk and arm were studied using an optoelectronic system. In the dynamic condition the target object, a cup, was moved by the robotic device along clockwise and counterclockwise circular trajectories. RESULTS Two main strategies were used to study the onset and offset of shoulder and elbow movements and their maximum velocities. The hand velocity profile was bell-shaped in the static condition and compatible with ramp movements for the more affected side in the dynamic condition. The time to object contact was higher for the more affected side in the dynamic condition. The temporal coordination index illustrated an immature and less flexible behaviour in childrens reaching in all the examined conditions. CONCLUSION Study of the hand velocity profiles, the time to object contact and the temporal coordination index highlighted, first, the dependence of upper limb interjoint coordination on task, context, residual resources and individual solution, and secondly, the sensory-motor deficit characteristics of the childrens more affected side during dynamic reaching, raising the prospect of a promising training context in children with hemiplegia.

Spasticity Measurement Based on Tonic Stretch Reflex Threshold in Children with Cerebral Palsy Using the PediAnklebot

Nowadays, objective measures are becoming prominent in spasticity assessment, to overcome limitations of clinical scales. Among others, Tonic Stretch Reflex Threshold (TSRT) showed promising results. Previous studies demonstrated the validity and reliability of TSRT in spasticity assessment at elbow and ankle joints in adults. Purposes of the present study were to assess: (i) the feasibility of measuring TSRT to evaluate spasticity at the ankle joint in children with Cerebral Palsy (CP), and (ii) the correlation between objective measures and clinical scores. A mechatronic device, the pediAnklebot, was used to impose 50 passive stretches to the ankle of 10 children with CP and 3 healthy children, to elicit muscles response at 5 different velocities. Surface electromyography, angles, and angular velocities were recorded to compute dynamic stretch reflex threshold; TSRT was computed with a linear regression through angles and angular velocities. TSRTs for the most affected side of children with CP resulted into the biomechanical range (95.7 ± 12.9° and 86.7 ± 17.4° for Medial and Lateral Gastrocnemius, and 75.9 ± 12.5° for Tibialis Anterior). In three patients, the stretch reflex was not elicited in the less affected side. TSRTs were outside the biomechanical range in healthy children. However, no correlation was found between clinical scores and TSRT values. Here, we demonstrated the capability of TSRT to discriminate between spastic and non-spastic muscles, while no significant outcomes were found for the dorsiflexor muscle.

Estimation of multivariable dynamic ankle impedance after botulinum toxin injection in children with cerebral palsy

The main object of this study is to quantify the effect of botulinum toxin on the dynamic ankle impedance (ZAnkle) in children with cerebral palsy (CP). The effect was evaluated by comparing the ZAnkle before and one month later the botulinum injection in gastrocnemius muscle. A cohort of six children with CP was involved in the study. All data were gathered by the pediatric version of the Anklebot (PediAnklebot), a backdrivable robot for ankle rehabilitation. The robot applied random torque perturbations to the ankle in both inversion-eversion (IE) and dorsi-plantar flexion (DP) direction. The ankle angular displacements and torques were gathered by encoders and load cells mounted on the PediAnklebot. The ZAnkle was estimated by a Multiple-Input Multiple-Output system identification (MIMO). The ZAnkle was evaluated in three frequency ranges: 0 Hz ≤ f ≤ 2 Hz, 2 Hz ≤ f ≤ 5 Hz, and 5 Hz ≤ f ≤ 8 Hz, addressed as low, mid and high frequency ranges. In each selected range the impedance anisotropy was quantified by the Direction Dependent Map (DDM) and the DDM shape was evaluated via the ZRatio, defined as the ratio between the maximum and the minimum value assumed by ZAnkle. Statistically significant decreases induced by the toxin treatment were found for ZAnkie in IE direction only in high frequency range and in DP direction for the three frequency ranges here examined. Moreover, a significant decrease of ZRatio emerged at mid frequency range. In conclusion, the botulinum toxin injection mainly affected the movement involving gastrocnemius, i.e. the dorsi-plantar flexion, and it did not affect the ankle impedance in inversion-eversion. These findings implied a clear variation of muscle elasticity and can provide an objective and quantitative support in the neurorehabilitation treatments of pediatric population with neurological diseases.