Distinct multi-joint control strategies in spastic diplegia associated with prematurity or Angelman syndrome

Spastic diplegia is commonly due to periventricular leucomalacia. associate d with premature birth. It is also a feature of Angelman syndrome (AS), a n eurogenetic disorder with developmental delay, absent speech and mirthful b ehaviour. We studied the kinematics and kinetics of the squatting movement and associated electromyographic (EMG) activities in 20 children with spast ic diplegia associated with periventricular leucomalacia (SDPL) or AS: and 18 unimpaired children. While movement of normal subjects consisted of vert ical translation of most body segments, the movement of SDPL children was o perated around the fixed knee with backward shift of the hip, and AS childr en performed a forward flexion of the trunk over the thigh. Trunk stability was correlated with movement velocity in both pathological groups. In norm al subjects, anticipatory EMG pattern consisted of silencing of hamstring m uscle tonic activity prior to movement onset. This deactivation was not pre sent in spastic diplegia. In SDPL, anticipatory overactivation of ankle joi nt actuators was recorded and tonic cocontraction persisted throughout the movement. In AS, rhythmic EMG bursting was seen during the movement. Should er, hip and knee trajectories in the sagittal plane showed marked within-gr oup stereotypies in orientation, shape and length. The patterns in both pat hological groups were therefore distinctive. We speculate that they reflect corticospinal impairment in SDPL and combined corticospinal and cerebellar dysfunction in AS. (C) 2001 Elsevier Science Ireland Ltd. All rights reser ved.