title: Auditory neural responses to click stimuli of different rates in the brainstem of very preterm babies at term.
abstract: Auditory neural responses to acoustic stimuli of different rates were studied by analyzing changes in brainstem auditory evoked responses (BAER) with increasing repetition rate of clicks, or rate-dependent changes, in 62 very preterm babies (gestation 24-32 wk). None had perinatal asphyxia or major complications at the time of testing (37-42 wk postconceptional age) to exclude their possible effects on the recorded BAER. As the rate of clicks was increased from 21/s to 51/s and 91/s, I-V interpeak interval in these babies increased similarly to that in normal term neonates. The rate-dependent change decreased significantly in I-III interval, but increased significantly in III-V intervals and III-V/I-III interval ratio (all p < 0.01). At all three rates of clicks, the I-V interval, the most commonly used BAER variable, tended to increase slightly but did not differ significantly from the term neonates. The I-III interval decreased significantly at higher click rates (ANOVA p < 0.05 at 51/s and < 0.001 at 91/s), whereas the III-V interval and III-V/I-III interval ratio increased significantly at all 21/s, 51/s, and particularly 91/s (p < 0.01-0.001). No abnormalities were found in wave V amplitude at any rates. These results suggest that very preterm babies have an advanced peripheral development of the brainstem auditory pathway but a retarded central development or central impairment. A nearly normal I-V interval does not exclude a possible abnormality in its subcomponents (I-III and III-V intervals). In babies who have a normal BAER at a conventionally used low rate of clicks, we cannot exclude an abnormal BAER at higher rates.
authors.affiliation: Neonatal Unit, Department of Paediatrics, John Radcliffe Hospital, University of Oxford, Headington, Oxford OX3 9DU, United Kingdom. zedong.jiang@padiatrics.ox.ac.uk
authors.forename: Ze D
authors.initials: ZD
authors.lastname: Jiang
authors.forename: Dorothea M
authors.initials: DM
authors.lastname: Brosi
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Wilkinson
mesh_terms: D000161:Acoustic Stimulation; D001306:Auditory Pathways / Q000254:growth & development; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008297:Male; D011247:Pregnancy; D012044:Regression Analysis; D013997:Time Factors