Bert J. Smit

Neurobehavioral and developmental profile of very low birthweight preterm infants in early infancy

Aim: To describe the neurobehavioral and developmental profile of very low birthweight (VLBW) preterm infants in early infancy. Methods: Twenty VLBW infants and 10 term control infants were assessed at term, 3 and 6 mo of age. Neurobehavioral assessments included the Neonatal Behavioral Assessment Scale (NBAS) at term; the Infant Behavioral Assessment at term, 3 and 6 mo of age and the Behavioral Rating Scale of the Bayley Scales of Infant Development—II (BSID‐II) at 3 and 6 mo of age. Development was evaluated with the Bayley Motor and Mental Scale at 3 and 6 mo. Results: At term age VLBW infants differed from term infants on all the clusters and supplementary items of the NBAS. VLBW infants also showed more stress and less approach behavior at term and 6 mo of age and more problems with self‐regulation in all subsystems at 6 mo of age. Moreover, VLBW infants performed lower on the Bayley Motor, Mental and Behavioral Rating Scale: 12 VLBW infants scored questionable or non‐optimal on the Psychomotor Development Index and 18 questionable or non‐optimal on the Behavioral Rating Scale. These results support the need for neurobehavioral intervention of VLBW infants in the first 6 mo of life.

Median nerve conduction velocity and central conduction time measured with somatosensory evoked potentials in thyroxine-treated infants with Down syndrome

OBJECTIVE. The aim of this study was to determine whether thyroxine treatment would improve nerve conduction in infants with Down syndrome. METHODS. A single-center, nationwide, randomized, double-blind, clinical trial was performed. Neonates with Down syndrome were assigned randomly to thyroxine (N = 99) or placebo (N = 97) treatment for 2 years. Daily thyroxine doses were adjusted regularly to maintain plasma thyrotropin levels in the normal range and free thyroxine concentrations in the high-normal range. The outcome measures were nerve conduction velocity and central conduction time, determined through median nerve somatosensory evoked potential recording, at the age of 24 months. RESULTS. At the age of 24 months, somatosensory evoked potential recordings for 81 thyroxine-treated and 84 placebo-treated infants were available for analysis. Nerve conduction velocity and central conduction time did not differ significantly between the 2 treatment groups (nerve conduction velocity: thyroxine: 51.0 m/second; placebo: 50.1 m/second; difference: 0.9 m/second; central conduction time: thyroxine: 8.83 milliseconds; placebo: 8.73 milliseconds; difference: 0.1 milliseconds). CONCLUSIONS. Postnatal thyroxine treatment of infants with Down syndrome did not alter somatosensory evoked potential-measured peripheral or central nerve conduction significantly. The absence of favorable effects suggests that pathologic mechanisms other than mild postnatal hypothyroidism underlie the impaired nerve conduction. The absence of adverse effects suggests that longstanding plasma free thyroxine concentrations in the high-normal range are not harmful to nerve maturation.

MOTOR NERVE CONDUCTION VELOCITY IN VERY PRETERM INFANTS IN RELATION TO THYROXINE SUPPLEMENTATION † 1057

Background: Transient hypothyroxinemia, which is common in very preterm infants, is related to an increased risk of neurodevelopmental dysfunction as well as to slow motor nerve conduction velocity (MNCV).