Rhythmical leg movements in low-risk and brain-damaged preterm infants.

The characteristics of rhythmical kicking movements of preterm infants with documented brain damage (BD), who later showed a severe motor impairment, are described and compared with those of low-risk (LR) preterm infants. Spontaneous movements were videotaped for 60 min in the incubator or in a warmer. A first group of 6 BD and 6 LR infants was observed at 31-35 weeks of postmenstrual age (PMA) and a second group (6 BD, 6 LR) at 37-39 weeks. Bouts of rhythmical kicks, defined as leg movements repeated in the same form at least three times at regular short intervals, were analysed during periods of activity. The results indicated non-significant differences between BD and LR infants at 31-35 weeks of PMA. In contrast, some differences were observed at 37-39 weeks. These differences were not due to leg movement frequency, but to inter-leg coordination and to temporal organisation of the kicking cycles. LR infants exhibited more alternate-leg movements and fewer semi-both-leg movements (simultaneous flexion and non-simultaneous extension) than BD infants. In LR cases the duration of the pause between flexion and extension was shorter, whereas flexion and extension periods were similar for all infants. Although there were significant differences, quantitative analysis of kicking characteristics was not clinically useful because of the large overlap in findings between the two groups. On the other hand Gestalt evaluation of general movements of the same videorecordings showed a closer correlation with the presence of brain lesions and with neurological outcome.