Symposium
Chair: Linda Fetters
Discussant: Carolyn B. Heriza
The work assembled for this symposium includes studies of the patterns ofcoordination in the development of movement of infants born prematurely.The four presentations in this symposium represent research fromlaboratories on four continents. These studies are unique, yet overlap inapproach, dependent measures and sample type. This will allow the audienceto compare the studies, yet gain insight into individual work on motordevelopment in prematurely born infants born and cared for within differentmedical and developmental environments.Very low birthweight (VLBW) infants born prematurely are at increased riskfor delayed or aberrant coordination of movement. VLBW infants withneonatal white matter disorder (NWMD) are at highest risk for neuromotorproblems including cerebral palsy. NWMD is a term now used to includegeneral damage to white matter including periventricular leuckomalacia andhemorrhage. Many studies have approached the understanding of the problemsof premature infants, VLBW infants and VLBW infants with NWMD by recordingmotor milestones, or with gross, dichotomous categorizations of neuromotorproblems such as cerebral palsy or no cerebral palsy. The research in thissymposium investigates the patterns of coordination fundamental to theachievement of functional movements that are captured as motor milestonesin most other studies of motor development and prematurity. Anunderstanding of these fundamental patterns of coordination could lead toimproved intervention and earlier intervention rather than waiting forfailed motor milestones.The presentations in this symposium include the range of prematurely borninfants from healthy, low risk premies to very sick, extremely high riskpremies with brain damage documented with magnetic resonance imaging. Eachof the four presentations uses kinematic analyses to investigate movement.The two studies of healthy premature and healthy VLBW infants demonstratewithin leg coordination patterns that are similar to healthy fullterm (FT)infants. The third study which includes VLBW infants with NMWD documentedwith MRI as well as healthy VLBW and FT infants demonstrates that thewithin leg coordination patterns are atypical as early as one month of agefor the VLBW infants with NMWD, but not for the other two groups. This iscritical information, as this is the group that is at highest risk for thelater development of spastic diplegic CP. The dependent measures used todescribe these coordination patterns in all of the studies include analysisof intralimb joint coupling through correlation and phase lag analysis. Thefourth study extends this type of analysis to 18 month old toddlers withNWMD on MRI. NMWD is associated with poor or no walking ability as well asatypical kinematic features for those subjects who could walk.This large body of data from four laboratories, from four continents,detailing fundamental patterns of coordination in premature infants is aunique opportunity for audience and presenters to analyze and discuss bothdata and the significance of the data for our understanding of prematuremotor development and for planning empirically driven interventionstrategies.
Details of individual items:
paper
Background and Purpose Very low-birthweight (VLBW) infants (birth bodyweight <1501 g and gestational age <37 weeks) are at increased risk formotor delays. Recent approaches to the remediation of motor disorders inpreterm infants have emphasized early identification and intervention. Thepurpose of this study was to use kinematic analysis to compare the kickingmovements between VLBW infants and normal term infants at 2 and 4 monthscorrected age. Subjects The study included 22 VLBW infants and 22demographically matched normal term infants who were born at NationalTaiwan University Hospital, Taipei, Taiwan. VLBW infants were furtherdivided into two groups: gestational age of 30 weeks and older andgestational age of <30 weeks. Methods Infants were prospectivelyevaluated for kicking movements at 2 and 4 months corrected age. Bilaterallower limb movements were recorded with four synchronized video cameras.The videotapes were digitized and analyzed using Peak Performance MotionAnalysis System with 3-dimensional analytic model. Kinematic variablesincluded kick frequency, spatio-temporal organization of the kick cycle,inter-joint coordination, and inter-limb coordination. Spatio-temporalvariables consisted of kick amplitude, flexion phase, intra-kick pause,extension phase, and inter-kick pause. Inter-joint coordination consistedof normalized phase lag between peak hip and knee flexion and pairwisejoint correlation between hip, knee, and ankle. Inter-limb coordinationwas measured by proportions of unilateral, synchronized, and alternate kickpattern. Results Normal term infants manifested striking stability insome features of kick, i.e. extension phase duration, hip-anklecoordination, knee-ankle coordination, and proportion of alternate kickpattern. Developmental changes were observed in other features. Normalterm infants tended to decrease kick frequency, increase kick amplitude,extend flexion phase, extend intra-kick pause, increase normalized phaselag between peak hip and knee flexion, lower hip-knee correlation, andincrease the proportion of synchronous kick pattern. Comparison of kickingmovements between groups revealed comparable developmental patterns amongVLBW infants and normal term infants. However, differences were found insome of the variables between the VLBW infants with youger gestational agesand normal term infants. The former exhibited an increase in kickfrequency and no change in flexion phase with advancing age. Discussionand Conclusion Our results demonstrated that the developmental changesof kicking movements of VLBW infants mostly resembled those of normal terminfants. The observed differences in the characteristics of kickingbetween groups appeared to be due to extreme prematurity. Future studiesneeds to follow preterm infants to older ages to determine whether theinitial differences in kicking movements could be used to predict laterdevelopmental outcome.
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Background and Purpose: Very low birthweight (VLBW) infants bornprematurely and with neonatal white matter disorder (NWMD) are at increasedrisk of developing spastic diplegia, a form of cerebral palsy. Onehallmark of the gait of children with spastic diplegia is an in-phase gait,i.e., with all joints flexed in a crouched or what has been described as a'Groucho Marks' gait. The purpose of our study was to investigate theearly coordination of leg movements of this high risk sample, in comparisonto a lower risk sample and to fullterm, healthy infants. We wereinterested in identifying possible antecedents of this later in-phasepattern and the natural history of diplegia. Subjects: Subjects were 20VLBW infants at one month corrected age and 10 fullterm (FT) controls atone month chronological age. Ten of the VLBW infants had documented NWMD.Group status for all infants was determined by magnetic resonance imaging.Method: Supine infants kicked spontaneously while watching the examiner.Leg movements were captured using Optotrak and video. Dependent variablesincluded correlation of hip, knee, and ankle joints, durations of movementflexion, extension and intrakick phases, range of extension and flexionmovements, and correlations between amplitude of movements and peakvelocities. In-phase movements were defined as high, positive jointcorrelations; out-of-phase movements as low positive or negativecorrelations. Results: VLBW infants with NWMD had significantly higherinterjoint correlations in ankle to knee and ankle to hip in comparison toFT and VLBW infants without NWMD. These results indicate that thedisassociation of ankle from knee and hip joint that normally begins at 1-2months in healthy FT infants and that was evident in our sample, had notbegun in the VLBW infants with NWMD. Fullterm and healthy VLBW infantsexhibited strong positive relations between amplitude of movements and peakvelocities while the VLBW infants with NWMD exhibited no relation betweenthose variables. This amplitude-velocity relation is typically found inskilled movements. Fullterm and VLBW infants without NWMD were more flexedin hip and knee joints at the initiation of leg movements than the VLBWinfants with NWMD, while at peak flexion the FT infants were more flexed inhip and knee joints than both the VLBW groups. Fullterm infants had asignificantly longer duration of the extension phase, but there were nosignificant differences in durations of the flexion or intrakick phases.These differences may be attributed to differences in flexor and extensortone among the groups. Conclusions: VLBW infants with NWMD have highercorrelations among intralimb joints than VLBW infants without NWMD or FTinfants indicating more restricted movement. The lack of anamplitude-velocity relation indicates abnormal relations of the underlyingcomponents of the leg movements. These infants may not adapt force outputto changes in intrinsic and extrinsic dynamics. Kinematic analysisdifferentiated characteristics of leg movements among the three groups ofinfants and may be an important tool in early prediction of neuromotordysfunction, including cerebral palsy. These infants are currently beingfollowed to 18 months of age to determine neuromotor status.
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For most of the 20th century, research on early infant motor developmentfocused primarily on either reflex activity, which was thought to be themajor precursor to later motor development, or observing and describing theprogression of the motor milestones. However, over the last two decades,there has been a growing interest in understanding the importance of earlyspontaneous activity on later motor development. Motion analysis has beenemployed to examine the changing relationship between joints duringactivities such as spontaneous kicking. This technique, based on thedynamical systems approach, has also been used to compare spontaneouskicking in fullterm and preterm infants. Two recent studies will bedescribed. The first examined the development of both intralimb andinterlimb coordination during spontaneous leg kicking in both fullterm andlow-risk preterm infants (born between 31 and 37 weeks gestational age).This longitudinal study investigated fourteen infants from age 4 weeks to24 weeks (corrected for prematurity). Changes in joint coupling andsynchrony were determined by measuring cross-correlations between the hip,knee and ankle joints of the right and left legs, and also the phase lagsbetween the angular displacement of each pair of joints. Resultsdemonstrated that while strong intralimb couplings were present throughoutthe period examined, the synchrony between the two legs gradually increasedas the infant became older. Different patterns of development were foundbetween fullterm and preterm infants, and also between the right and leftleg. This research has been extended in a study investigating thedevelopment of coordination between all four limbs. In order for an infantto develop appropriate skills such as creeping and climbing, all four limbsneed to be appropriately coordinated. Previous research on spontaneousactivity has suggested that this is not present initially and develops overthe first few months. Using 3-D motion analysis, these relationships wereexamined in both fullterm and preterm infants. Results are discussed interms of their implications for understanding the processes involved inearly motor development and appropriate intervention strategies for infantsat risk of motor disability.
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The aim of the present project is to compare the walking abilities inchildren with and without periventricular leukomalacia (PVL) and to seewhether there are relations between the brain damage (localisation andseverity of the lesions), diagnosed on the basis of a MRI scan at 18months, and the locomotion capability of the children. The walkingability is analysed in infants diagnosed as high-risk preterm at birth (n 46) and in a control group of 6 healthy term-born infants. The infants ofthe high-risk group were followed longitudinally since their birth and cameat 18 months for the walking test. The infants of the healthy group cametwice a month during the first two months of independent walking (IW) andthen once a month. All the high-risk preterm born infants had a MRI scanat 18 months. The grading of PVL from the MRI images took into accountseveral aspects: (1) the type of white matter damage (gliosis/cysts/whitematter loss); (2) the localisation of the PVL; (3) extensiveness of thewhite matter damage (periventricular/subcortical areas). PVL was gradedaccording to a global MRI score from 1 (no PVL) to 6 (multicysticencephalopathy/total white matter damage). The analysis of the independent walking ability includes the recording ofdifferent locomotor parameters that were divided in two categories: theglobal performance parameters and parameters indicating how the performanceis achieved. The global performance parameters were chosen to give ageneral view of the functional level of walking: mean progression velocity,step length and width, lateral acceleration of the centre of mass andrelative double-support time (calculated from force plate data). Aqualitative assessment of walking was made to see how the performance wasachieved. Arm posture and movements as well as the positioning of the feetat floor contact (occurrence of heelstrikes) were analysed from videofilms. The inter-individual variation between the values of the infants ofthe control group was used as the normal range to which the infants of thehigh-risk group were compared.The findings are: The majority of the high-risk preterm born infants withno, minimal or moderate PVL showed walking performance that was within therange of the control group infants. Infants with a severe PVL (MRI globalscore 5 and 6) were not able to walk at 18 months. Some individuals of thehigh-risk group showed either lower performances on some global parameters,or differences according to the qualitative analysis or a combination ofboth. This means, for example, that a child can reach a normal globalwalking performance (velocity, step length, lateral balance) with abnormalsegmental organization, i.e. posture/movement of the arms and occurrence ofheelstrikes. Put together the data showed that for the children with aglobal score of 1 (no PVL) up to 4 (extension of gliosis/cysts slightlybeyond than the periventricular white matter) no clear relation betweenwalking performance and MRI scores was found.* Acknowledgment: This research was supported by the 'Fonds JohannaStichting'.