[Evaluation and analysis of auditory function and its clinical characteristics in low birth weight premature infants.].
OBJECTIVE
To investigate and analyze dynamic changes of auditory function in premature babies with fetal age of less than 37 weeks who were categorized into different birth weight groups and to detect abnormalities of auditory function in these babies and to describe the early development patterns of auditory function in infancy.


METHODS
Total of 252 subjects (504 ears) from neonatal ward, neonatal intensive care unit and auditory clinic in Guangzhou Children Hospital, whose fetal age were less than 37 weeks, were included in our study and received auditory function evaluation from January 2004 to February 2008. To investigate the correlation between birth weight and development and abnormality of auditory function in premature babies, all subjects were divided into four groups according to birth weight: </= 1.50 kg, 1.51 - 2.00 kg, 2.01 - 2.50 kg and > 2.5 kg. Each group was further categorized by subject's age on first auditory function evaluation in 0 - 3 months (include 3 months), 3 - 6 months (include 6 months) and above 6 months, respectively. Subjects who were evaluated more than once in different age frame would be grouped into multiple evaluation subgroups. All subjects underwent one or more objective auditory examinations including auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), tympanometry and acoustic stapedius reflex.


RESULTS
A tendency of decreased wave V threshold of ABR was seen as birth weight increased, while the percentage of subjects with ABR wave V threshold </= 40 dB nHL increased as well. A tendency of decreased wave V threshold of ABR was also seen as age increased after birth, likewise the percentage of subjects with ABR wave V threshold </= 40 dB nHL increased with age after birth. For multiple evaluation subgroups, improvement rate ranged from 56.67% to 82.76% depending on subjects' birth weight. In all low birth weight (LBW) premature babies, 4 subjects and 6 ears with no wave or just wave V at maximum stimulation 103 dB nHL in ABR were diagnosed with auditory neuropathy, giving an incidence of 3.75%(by ears).


CONCLUSIONS
Auditory function (including middle ear and auditory nerve system) of premature LBW improved gradually within examined age frame, as birth weight and age after birth increased. For LBW preterm who showed abnormality in auditory evaluation, a 6-month follow-up should be scheduled, babies weighted less than 1.50 kg at birth that showed abnormality in the first auditory evaluation should be re-evaluated within 2 months. Babies weighted more than 1.50 kg who showed abnormality in the first auditory evaluation should be re-evaluated within 3 months.
Luo
Ren-Zhong
RZ
Depatment of otorhinolaryngology, Guangzhou Women and Children's Medical Center, Guangzhou Children's Hospital, Guangzhou 510120, China. Email: luorenzhong@21cn.com.
Wang
Xiao-Ya
XY
Wen
Rui-Jin
RJ
Zhou
Jia-Lin
JL
Liang
Jian
J
Huang
Zhen-Yun
ZY
Gao
Sheng-Li
SL
Chen
Qian
Q
D001309:Auditory Threshold; D016057:Evoked Potentials, Auditory, Brain Stem; D006309:Hearing; D006801:Humans; D007223:Infant; D007230:Infant, Low Birth Weight; D007234:Infant, Premature; D015997:Neonatal Screening