Functional impairment of the brainstem in infants with bronchopulmonary dysplasia

Objectives. To gain new insights into the influence of bronchopulmonary dysplasia on the immature brain and to detect abnormalities, we studied the functional integrity of the brainstem in infants with bronchopulmonary dysplasia. Methods. Forty-one very preterm infants with bronchopulmonary dysplasia were studied at postconceptional ages of 37 to 42 weeks. Brainstem auditory evoked responses were recorded and analyzed by using the maximal length sequence technique. Results. Compared with term control subjects, wave V latency in the maximal length sequence brainstem auditory evoked response of the infants with bronchopulmonary dysplasia increased significantly at all 91 to 910 clicks per second rates. Similarly, I-V and particularly III-V interpeak intervals increased significantly. The III-V/I-III interval ratio also increased significantly at all click rates. All of these abnormalities became more significant as the click rate was increased. Compared with healthy, very preterm control subjects, all of these maximal length sequence brainstem auditory evoked response variables increased significantly at all click rates, although the differences between the 2 groups were slightly smaller than those between the infants with bronchopulmonary dysplasia and the term control subjects. The wave I and III latencies and I-III interval in the infants with bronchopulmonary dysplasia did not show any abnormalities. The slopes of the wave V latency-rate function and I-V and particularly III-V interval-rate functions for the infants with bronchopulmonary dysplasia were significantly steeper than those for both term and healthy, very preterm control subjects. The slope of the III-V/I-III interval ratio-rate function for the infants with bronchopulmonary dysplasia was also significantly steeper than those for the 2 control groups. Conclusions. The results suggest poor myelination and synaptic function of the brainstem in infants with bronchopulmonary dysplasia, resulting in impaired functional integrity. In comparison, peripheral neural function was relatively intact.