Development of postural adjustments during reaching in preterm infants

Preterm infants often show postural abnormalities, such as hyperextension of neck and trunk, which can interfere with motor and cognitive development. Little is, however, known on the pathophysiology of postural development in preterm infants. Therefore, we longitudinally studied the development of postural adjustments during reaching movements in 12 preterm infants between the (corrected) ages of 4 and 18 mo. Five infants showed minor neurological dysfunctions at 18 mo, such as a mild diffuse hypotonia, a mild hypertonia of the legs, or a mild asymmetry in posture and motility, and seven infants were neurologically normal. Each assessment consisted of a simultaneous recording of video-data and surface electromyograms of arm, neck, trunk, and leg muscles during reaching in various lying and sitting positions. Comparable data on postural development in ten full-term infants were available. The preterm infants showed an excessive amount of postural activity during reaching movements at all ages studied. Moreover, the postural adjustments were temporally disorganized and could not be modulated with respect to the velocity of the arm movement and the initial sitting position. We hypothesized that the preterms' disability to modulate their postural adjustments might be due to a reduced capacity to learn from prior experience. In our small group the postural dysfunctions were not related to the presence of hyperextension at early ages, to the neurological outcome at 18 mo, or to the lesions found on the neonatal brain ultrasound scans.