Hulecki Lauren R, Small Susan A
School of Audiology and Speech Sciences, University of British Columbia, Vancouver, Canada.
J Am Acad Audiol. 2011 Feb;22(2):81-92. doi: 10.3766/jaaa.22.2.3.
Bone-conduction thresholds have been used in audiologic assessments of both infants and adults to differentiate between conductive and sensorineural hearing losses. However, air- and bone-conduction thresholds estimated for infants with normal hearing using physiological measures have identified an "air-bone gap" in the low frequencies that does not result from conductive hearing impairment but, rather, from maturational differences in sensitivity. This maturational air-bone gap appears to be present up to at least 2 yr of age. Because most infants older than 6 mo of age are clinically assessed behaviorally, rather than physiologically, it is necessary to determine whether a similar maturational air-bone gap is present for behavioral air- and bone-conduction thresholds.
The purpose of this study was to estimate behavioral bone-conduction thresholds for infants using a standard clinical visual reinforcement audiometry (VRA) protocol to determine whether frequency-dependent maturational patterns exist as previously reported for physiological bone-conduction thresholds.
Behavioral bone-conduction minimum response levels were estimated at 500, 1000, 2000, and 4000 Hz using VRA for each participant.
Young (7-15 mo; N = 17) and older (18-30 mo; N = 20) groups of infants were assessed. All infants were screened and considered to be at low risk for hearing loss.
Preliminary "normal levels" were determined by calculating the 90th percentile for responses present as a cumulative percentage. Mean bone-conduction thresholds were compared and analyzed using a mixed-model analysis of variance across frequency and age group. Linear regression analysis was also performed to assess the effect of age on bone-conduction thresholds.
Results of this study indicate that, when measured behaviorally, infants under 30 mo of age show frequency-dependent bone-conduction thresholds whereby their responses at 500 and 1000 Hz are significantly better than those at 2000 and 4000 Hz. However, thresholds obtained from the younger group of infants (mean age of 10.6 mo) were not significantly different from those obtained from the older group of infants (mean age of 23.0 mo) at any frequency.
The findings of the present study are similar to the results obtained from previous physiological studies. Compared to previously documented air-conduction thresholds of infants using similar VRA techniques, a maturational air-bone gap is observed in the low frequencies. Therefore, differences between infant and adult bone-conduction thresholds persist until at least 30 mo of age. As a result, different "normal levels" should be used when assessing bone-conduction hearing sensitivity of infants using behavioral methods.
骨导阈值已用于婴儿和成人的听力评估，以区分传导性听力损失和感音神经性听力损失。然而，使用生理测量方法对听力正常的婴儿估计的气导和骨导阈值发现，低频存在“气骨间隙”，这并非由传导性听力障碍导致，而是由敏感性的成熟差异引起。这种成熟性气骨间隙似乎至少在2岁之前都存在。由于大多数6个月以上的婴儿是通过行为学而非生理学方法进行临床评估的，因此有必要确定行为气导和骨导阈值是否也存在类似的成熟性气骨间隙。
本研究的目的是使用标准的临床视觉强化测听法（VRA）协议估计婴儿的行为骨导阈值，以确定是否存在如先前报道的生理骨导阈值那样的频率依赖性成熟模式。
使用VRA对每位参与者在500、1000、2000和4000赫兹处估计行为骨导最小反应水平。
对年轻组（7 - 15个月；N = 17）和年长组（18 - 30个月；N = 20）的婴儿进行评估。所有婴儿均经过筛查，被认为听力损失风险较低。
通过计算作为累积百分比出现的反应的第90百分位数来确定初步的“正常水平”。使用跨频率和年龄组的混合模型方差分析对平均骨导阈值进行比较和分析。还进行了线性回归分析以评估年龄对骨导阈值的影响。
本研究结果表明，在进行行为测量时，30个月以下的婴儿表现出频率依赖性骨导阈值，即他们在500和1000赫兹处的反应明显优于在2000和4000赫兹处的反应。然而，在任何频率下，较年轻婴儿组（平均年龄10.6个月）获得的阈值与较年长婴儿组（平均年龄23.0个月）获得的阈值均无显著差异。
本研究结果与先前生理研究的结果相似。与先前使用类似VRA技术记录的婴儿气导阈值相比，在低频观察到成熟性气骨间隙。因此，婴儿和成人骨导阈值之间的差异至少持续到30个月龄。因此，在使用行为方法评估婴儿的骨导听力敏感性时应使用不同的“正常水平”。
