One-third of term babies after perinatal hypoxia-ischaemia have transient hearing impairment: dynamic change in hearing threshold during the neonatal period.
OBJECTIVE
To examine the process of change in hearing threshold during the neonatal period after perinatal hypoxia-ischaemia.


METHODS
The threshold of brainstem auditory evoked responses (BAER) was measured serially during the first month after birth in 92 term babies who suffered hypoxia-ischaemia.


RESULTS
The mean BAER threshold in these babies was significantly increased on day 1 (ANOVA p < 0.001). The elevated threshold decreased progressively on days 3 and 5, but was still significantly higher than that in normal controls (p < 0.01). The elevation continuously decreased more slowly on days 10 and 15, and to a near normal level on day 30. Threshold elevation was seen in 31.7% of the babies on day 1, and 34.5% during the first three days. The rate of elevation decreased progressively thereafter. On day 30, 10.6% of the subjects still had increased thresholds. Moderate to severe elevation occurred mainly during the first week and severe elevation occurred predominately on day 1. Threshold elevation starting after days 3-5 is likely to be due to middle-ear disorders. As a whole, during the first month, 44.6% (41/92) of the babies studied had threshold elevation. BAER threshold was correlated weakly with the stage of hypoxic-ischaemic encephalopathy on days 1 and 3. The threshold was significantly higher in babies with severe encephalopathy than in those with mild or moderate encephalopathy during the first 3 d of life.


CONCLUSIONS
Hearing threshold is elevated in about one-third of term babies after hypoxia-ischaemia. The elevated threshold decreases progressively after birth, and returns to normal by one month in most babies. The threshold correlates weakly with the severity of encephalopathy.
Children's Hospital, Fudan University, Shanghai. zedong.jiang@paediatrics.ox.ac.uk
Z D
ZD
Jiang
J
J
Wang
D M
DM
Brosi
X M
XM
Shao
A R
AR
Wilkinson
D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D005865:Gestational Age; D034381:Hearing Loss / Q000209:etiology*; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000150:complications*; D007231:Infant, Newborn; D008297:Male