Konopka Wiesław, Olszewski Jurek
Zakład Diagnostyki Audiologicznej i Elektrofizjologicznej Katedry Chirurgii Głowy i Szyi Uniwersytetu Medycznego.
Otolaryngol Pol. 2005;59(5):731-6.
Typical high frequency hearing loss is accompanied by an exaggerated response to loudness as the sound level exceeds your elevated thresholds. This exaggerated response to sound levels is termed "recruitment". Recruitment is a paradoxical phenomenon present in hearing losses due to cochlear damage. Loudness recruitment is usually present to some degree as measured on the SISI. There have been many explanation connected this phenomena so far. It has been suggested that otoacoustic emissions might be more sensitive in assessment of changes to the cochlea caused by noise than pure tone audiometry.
In the present study results of the short increment sensitivity index test (SISI), DPOAE as well as slope of DPOAE input/output (I/O) function were compared before and after noise exposure. The I/O function plots DPOAE amplitude as a function of the level of the primary tones, for the progressively increasing stimulus levels (from 45 to 70 dB SPL) for the frequencies 1, 2, 3, 4, 6, 8 kHz. From 40 patients between 18-21 years, 30 ears were extracted with cochlear lesions and good hearing.
Both, PTA and DPOAEs amplitude showed in this group significant reduction due to noise exposure. Slopes of the DPOAE I/O function were depended on stimulus levels. For the low intensity stimuli levels (45-55 dB SPL) we obtained DP I/O amplitude value worse than before noise exposure. When stimulus level was above 55 dB SPL for the frequencies (1, 2, 3, 4, 6, 8 kHz) the amplitude and DP I/O slope was higher than before noise exposure. We did not notice that phenomena in persons without cochlear lesions.
Our results showed that in examination group with cochlear lesion I/O DP amplitude was higher using stimulus level above 55 dB SPL. This notice can be otoacoustic recruitment phenomena.
典型的高频听力损失伴随着当声级超过升高的阈值时对响度的夸张反应。这种对声级的夸张反应被称为“重振”。重振是一种在因耳蜗损伤导致的听力损失中出现的矛盾现象。在短增量敏感指数（SISI）测试中，通常会在一定程度上出现响度重振。到目前为止，已经有许多关于这种现象的解释。有人提出，耳声发射在评估噪声对耳蜗造成的变化方面可能比纯音听力测定更敏感。
在本研究中，比较了噪声暴露前后短增量敏感指数测试（SISI）、畸变产物耳声发射（DPOAE）以及DPOAE输入/输出（I/O）函数斜率的结果。I/O函数将DPOAE幅度绘制为基频水平的函数，对于1、2、3、4、6、8千赫的频率，刺激水平逐渐增加（从45到70分贝声压级）。从40名18至21岁的患者中，提取出30只患有耳蜗病变且听力良好的耳朵。
该组中，由于噪声暴露纯音听阈（PTA）和DPOAE幅度均显著降低。DPOAE I/O函数的斜率取决于刺激水平。对于低强度刺激水平（45 - 55分贝声压级），我们得到的DPOAE I/O幅度值比噪声暴露前更差。当频率（1、2、3、4、6、8千赫）的刺激水平高于55分贝声压级时，幅度和DPOAE I/O斜率高于噪声暴露前。我们在没有耳蜗病变的人身上未发现这种现象。
我们的结果表明，在患有耳蜗病变的检查组中，使用高于55分贝声压级的刺激水平时，DPOAE I/O幅度更高。这种现象可能是耳声发射重振现象。
