Department of Audiology, All India Institute of Speech and Hearing, Mysore, India.
Behav Brain Funct. 2008 Apr 2;4:17. doi: 10.1186/1744-9081-4-17.
Otitis media (OM) leads to significant reduction in the hearing sensitivity. The reduced auditory input, if in the early years of life when the auditory neural system is still maturing, may adversely influence the structural as well as functional development of the system. Past research has reported abnormalities in both the structure and function of brainstem nuclei following auditory deprivation, but, it has not necessarily focused on children who had OM in their first year of life. It can also be said that if auditory processing is affected at the brainstem level because of early onset OM (reduced auditory input in the crucial periods of neural development), then, it may be said that auditory processing is also affected at the cortical level because it receives distorted input from the brainstem. Therefore, the purpose of this study was to document the effects of early onset OM on auditory processing, if any, at the brainstem as well as at cortical levels. A related purpose of the study was to investigate the persistence of the effects of early onset OM, if any, on auditory processing.
A cross sectional approach and a standard group comparison design was used in the study. Thirty children, who had OM between 6 and 12 months of age and who were in the age range of 3.1 - 5.6 years participated in the study. Children with OM were divided into 3 groups based on their age. Click evoked auditory brainstem responses (ABRs) and late latency responses (LLRs) were recorded from these children, and the responses were compared with those from age and gender matched normal children without any history of OM. The data from the 2 groups was statistically analyzed through independent t test. Pearson's Product Moment correlation was computed to examine the relationship between results of ABR and LLR in children with early onset OM.
The mean central conduction time was significantly increased and the mean amplitude of wave I and III of ABRs was significantly reduced in children with early onset OM compared to normal children. Also, the latency of all LLR waves was significantly less in children with early onset OM than in normal children. However, significant differences in mean values of either ABR or LLR (latencies or interwave intervals as the case may be) were observed only in 3-year old children. There was a significant, but negative association between central conduction time and latency of LLRs.
OM in the first year of life leads to negative effects on brainstem signal processing even if it has occurred only for a short duration (maximum of 3 months). In such a situation, auditory cortical structures probably show compensatory changes through central gain to offset the prolonged central conduction time. Although the results of the present study showed that the negative effects of early onset OM (occurring in the first year of life) on auditory processing disappeared by the time the children were 4.1 years, there is need for longitudinal studies on this to confirm the findings.
中耳炎（OM）会导致听力敏感度显著降低。如果听觉神经系统仍在成熟的早期，减少的听觉输入可能会对系统的结构和功能发育产生不利影响。过去的研究报告称，听觉剥夺后脑干核团的结构和功能都存在异常，但不一定集中在生命第一年患有 OM 的儿童身上。也可以说，如果由于早期 OM（在神经发育的关键时期减少听觉输入）而在脑干水平上影响听觉处理，那么由于它从脑干接收扭曲的输入，因此也可能在皮质水平上影响听觉处理。因此，本研究的目的是记录早期 OM 是否对脑干和皮质水平的听觉处理产生任何影响。该研究的一个相关目的是调查早期 OM 的任何影响（如果有）对听觉处理的持续时间。
本研究采用了横断面方法和标准组比较设计。30 名年龄在 3.1 至 5.6 岁之间、6 至 12 个月大的患有 OM 的儿童参加了研究。根据年龄将患有 OM 的儿童分为 3 组。从这些儿童中记录点击诱发的听觉脑干反应（ABR）和晚期反应（LLR），并将其与无 OM 病史的年龄和性别匹配的正常儿童的反应进行比较。通过独立 t 检验对两组数据进行统计分析。计算 Pearson 乘积矩相关系数，以检查早期 OM 儿童 ABR 和 LLR 结果之间的关系。
与正常儿童相比，早期 OM 儿童的 ABR 的中央传导时间明显延长，I 波和 III 波的平均振幅明显降低。此外，早期 OM 儿童的所有 LLR 波的潜伏期均明显短于正常儿童。然而，仅在 3 岁儿童中观察到 ABR 或 LLR 的平均值（视情况而定，为 ABR 或 LLR 的平均值）存在显著差异。中央传导时间与 LLR 潜伏期之间存在显著但负相关。
即使 OM 仅持续很短时间（最长 3 个月），也会对生命第一年的脑干信号处理产生负面影响。在这种情况下，听觉皮质结构可能会通过中枢增益发生代偿性变化，以抵消延长的中枢传导时间。尽管本研究结果表明，生命第一年发生的早期 OM（发生在生命的第一年）对听觉处理的负面影响在儿童 4.1 岁时消失，但需要对此进行纵向研究以确认这些发现。
