Changes in otolith VOR to off vertical axis rotation in infants learning to walk. Preliminary results of a longitudinal study

Head and eyes: Looking behavior in 12- to 24-month-old infants

This study demonstrates evidence for a foundational process underlying active vision in older infants during object play. Using head-mounted eye-tracking and motion capture, looks to an object are shown to be tightly linked to and synchronous with a stilled head, regardless of the duration of gaze, for infants 12 to 24 months of age. Despite being a developmental period of rapid and marked changes in motor abilities, the dynamic coordination of head stabilization and sustained gaze to a visual target is developmentally invariant during the examined age range. The findings indicate that looking with an aligned head and eyes is a fundamental property of human vision and highlights the importance of studying looking behavior in freely moving perceivers in everyday contexts, opening new questions about the role of body movement in both typical and atypical development of visual attention.

Locomotor patterns during obstacle avoidance in children with cerebral palsy

Previous studies mainly evaluated the neuromuscular pattern generation in cerebral palsy (CP) during unobstructed gait. Here we characterized impairments in the obstacle task performance associated with a limited adaptation of the task-relevant muscle module timed to the foot lift during obstacle crossing. Impaired task performance in children with CP may reflect basic developmental deficits in the adaptable control of gait when the locomotor task is superimposed with the voluntary movement.

How sacculo-collic function assessed by cervical vestibular evoked myogenic Potentials correlates with the quality of postural control in hearing impaired children?

OBJECTIVE

Functional integrity of vestibular end organs is essential for gaze stabilization, dynamic visual acuity, postural control and spatial orientation. Some authors hypothesized on the importance of saccules for postural control and motor development in children, including achievements such as standing up and walking. The purpose of this article was to observe how saccular dysfunction assessed by cervical Vestibular Evoked Myogenic Potentials (cVEMPs) correlates with the quality of postural control in non-syndromic deaf children.

METHOD

Seventy-six non-syndromic hearing-impaired children were retrospectively included. Sacculo-collic pathway was assessed with cVEMPs elicited in bone conduction. The response was quoted "normal" if a reproducible wave P13-N23 of at least 50μV in amplitude was present, if not, it was quoted "absent". The sample was divided in 3 groups depending on the presence of the sacculo-collic responses: normal bilateral group (Group 1), normal unilateral (Group 2) and absent bilaterally group (Group 3). Motor assessment was achieved with Movement Assessment Battery for Children, second edition (MABC-2). Postural control (PC) was assessed using the dynamic Balance Quest platform. The scores obtained with MABC-2, and the postural parameters recorded on the Balance Quest platform (sway of Centre of Pressure and spectral power index) were analyzed and compared throughout the groups.

RESULTS

Group 1 (normal bilateral) showed the best scores regarding motor abilities and postural stability within available normative data. Group 3 (absent bilateral) had the lowest motor and postural control skills. A good correlation between the scores obtained by MABC-2 motor test and dynamic posturography (Balance Quest) was observed.

CONCLUSIONS

The presence of at least one sacculo-collic response would predict satisfactory static and dynamic motor and postural control skills in non-syndromic hearing-impaired children. MABC-2 and Dynamic Posturography Balance Quest appears reliable and comparable tools for PC assessment in hearing impaired children. In the light of these results, it appears that in young children candidates for uni- or bilateral CI whose walking is not yet acquired, should receive a vestibular assessment before surgery to avoid the risk of bilateral sacculo-collic function impairment.

Zebrafish models of human eye and inner ear diseases

Eye and inner ear diseases are the most common sensory impairments that greatly impact quality of life. Zebrafish have been intensively employed to understand the fundamental mechanisms underlying eye and inner ear development. The zebrafish visual and vestibulo-acoustic systems are very similar to these in humans, and although not yet mature, they are functional by 5days post-fertilization (dpf). In this chapter, we show how the zebrafish has significantly contributed to the field of biomedical research and how researchers, by establishing disease models and meticulously characterizing their phenotypes, have taken the first steps toward therapies. We review here models for (1) eye diseases, (2) ear diseases, and (3) syndromes affecting eye and/or ear. The use of new genome editing technologies and high-throughput screening systems should increase considerably the speed at which knowledge from zebrafish disease models is acquired, opening avenues for better diagnostics, treatments, and therapies.

Immature Spinal Locomotor Output in Children with Cerebral Palsy

Detailed descriptions of gait impairments have been reported in cerebral palsy (CP), but it is still unclear how maturation of the spinal motoneuron output is affected. Spatiotemporal alpha-motoneuron activation during walking can be assessed by mapping the electromyographic activity profiles from several, simultaneously recorded muscles onto the anatomical rostrocaudal location of the motoneuron pools in the spinal cord, and by means of factor analysis of the muscle activity profiles. Here, we analyzed gait kinematics and EMG activity of 11 pairs of bilateral muscles with lumbosacral innervation in 35 children with CP (19 diplegic, 16 hemiplegic, 2-12 years) and 33 typically developing (TD) children (1-12 years). TD children showed a progressive reduction of EMG burst durations and a gradual reorganization of the spatiotemporal motoneuron output with increasing age. By contrast, children with CP showed very limited age-related changes of EMG durations and motoneuron output, as well as of limb intersegmental coordination and foot trajectory control (on both sides for diplegic children and the affected side for hemiplegic children). Factorization of the EMG signals revealed a comparable structure of the motor output in children with CP and TD children, but significantly wider temporal activation patterns in children with CP, resembling the patterns of much younger TD infants. A similar picture emerged when considering the spatiotemporal maps of alpha-motoneuron activation. Overall, the results are consistent with the idea that early injuries to developing motor regions of the brain substantially affect the maturation of the spinal locomotor output and consequently the future locomotor behavior.

Vestibular Disorders in Children With Congenital Cytomegalovirus Infection

BACKGROUND

Congenital cytomegalovirus (CMV) infection is the leading infectious cause of neurologic disabilities and sensorineural hearing loss in children. Sensorineural hearing loss prevalence in CMV suggests a viral tropism for the inner ear. Vestibular disorders induced by CMV infection are underestimated. This is the largest and most thorough study to assess the incidence of vestibular disorders and their correlation with hearing thresholds in children with CMV.

METHODS

This retrospective study assessed a cohort of 52 children with congenital CMV infection and sensorineural impairment who received a complete hearing and vestibular assessment. Vestibular evaluation included clinical examination, caloric bithermal test, earth vertical axis rotation, off-vertical axis rotation, and vestibular evoked myogenic potential. The prevalence, progression, and clinical impact of vestibular disorders were studied and correlated with hearing thresholds and the severity of congenital CMV infection.

RESULTS

Forty-eight children (92.3%) had hearing loss and vestibular disorders. Of those, vestibular disorders were complete and bilateral in 33.3%, partial and bilateral in 43.7%, and partial and unilateral in 22.9%. Serial testing in 14 children showed stable vestibular function in 50% and deterioration in 50%. Congenital CMV infection has a negative impact on postural development that is correlated with neurologic and vestibular impairment. Vestibular disorders were significantly associated with hearing disorders, but their respective severities showed no concordance.

CONCLUSIONS

Vestibular disorders are frequent and severe in CMV-infected children. Routine screening and appropriate management of vestibular lesions is essential to initiate adapted care.

Kinematics in Newly Walking Toddlers Does Not Depend Upon Postural Stability

When a toddler starts to walk without support, gait kinematics and electromyographic (EMG) activity differ from those of older children and the body displays considerable oscillations due to poor equilibrium. Postural instability clearly affects motor patterns in adults, but does instability explain why toddlers walk with a different gait? Here we addressed this question by comparing kinematics and EMGs in toddlers performing their first independent steps with or without hand or trunk support. Hand support significantly improved postural stability and some general gait parameters, reducing percent of falls, step width, lateral hip deviations and trunk oscillations. However, the kinematic and EMG patterns were unaffected by increased postural stability. In particular, the co-variance of the angular motion of the lower limb segments, the pattern of bilateral coordination of the vertical movement of the two hip joints, high variability of the foot path, the elliptic or single peak trajectory of the foot in the swing phase, and characteristic EMG bursts at foot contact remained idiosyncratic of toddler locomotion. Instead the toddler pattern shared fundamental features with adult stepping in place, suggesting that toddlers implement a mixed locomotor strategy, combining forward progression with elements of stepping in place. Furthermore, gait kinematics remained basically unchanged until the occurrence of the first unsupported steps and rapidly matured thereafter. We conclude that idiosyncratic features in newly walking toddlers do not simply result from undeveloped balance control but may represent an innate kinematic template of stepping.

Kinematics in Newly Walking Toddlers Does Not Depend Upon Postural Stability

When a toddler starts to walk without support, gait kinematics and electromyographic (EMG) activity differ from those of older children and the body displays considerable oscillations due to poor equilibrium. Postural instability clearly affects motor patterns in adults, but does instability explain why toddlers walk with a different gait? Here we addressed this question by comparing kinematics and EMGs in toddlers performing their first independent steps with or without hand or trunk support. Hand support significantly improved postural stability and some general gait parameters, reducing percent of falls, step width, lateral hip deviations and trunk oscillations. However, the kinematic and EMG patterns were unaffected by increased postural stability. In particular, the co-variance of the angular motion of the lower limb segments, the pattern of bilateral coordination of the vertical movement of the two hip joints, high variability of the foot path, the elliptic or single peak trajectory of the foot in the swing phase, and characteristic EMG bursts at foot contact remained idiosyncratic of toddler locomotion. Instead the toddler pattern shared fundamental features with adult stepping in place, suggesting that toddlers implement a mixed locomotor strategy, combining forward progression with elements of stepping in place. Furthermore, gait kinematics remained basically unchanged until the occurrence of the first unsupported steps and rapidly matured thereafter. We conclude that idiosyncratic features in newly walking toddlers do not simply result from undeveloped balance control but may represent an innate kinematic template of stepping.

Head coordination as a means to assist sensory integration in learning to walk

After a brief presentation of the development of free walking interpreted as learning dynamical equilibrium, the problem of sensory integration in the process of walking development is discussed. A critical review of the role of vision in the development of posturo-locomotor task is presented, along with recent test results on the development of the vestibular system. A final section presents the development of head stabilization and coordination as a necessary means to assist sensory integration. It is suggested that if sensory information is necessary to enhance posturo-locomotor skills, a good mastery of walking is in turn necessary to increase the efficiency of sensory integration.