Paglialonga Alessia, Del Bo Luca, Ravazzani Paolo, Tognola Gabriella
Istituto di Ingegneria Biomedica, Consiglio Nazionale delle Ricerche, Piazza Leonardo da Vinci 32, Milan, Italy.
Auris Nasus Larynx. 2010 Jun;37(3):291-8. doi: 10.1016/j.anl.2009.09.009. Epub 2009 Oct 29.
Aim of this study was to investigate the possible role played by outer hair cells and cochlear efferent system functionality when tinnitus develops in normal hearing ears. A multiparametric approach was used, entailing recording and analysis of a set of otoacoustic emissions (OAEs): distortion product (DPOAEs), transient evoked (TEOAEs) and efferent-mediated TEOAE suppression in the presence of contralateral acoustic stimulation (CAS).
Fifty-four subjects with normal hearing sensitivity participated in the study. Twenty-three suffered from chronic subjective tinnitus whereas thirty-one did not have tinnitus and acted as control subjects. DPOAEs were measured with eliciting tones of frequency ratio 1.22 and intensity 65 and 55dB SPL in the frequency range 0.5-8kHz. TEOAEs were recorded with the 'linear' protocol using clicks at 60dB peak SPL both in the absence and in the presence of CAS at two different intensities. DPOAE amplitude, TEOAE amplitude, and TEOAE suppression were analysed as relevant parameters.
Significantly reduced DPOAE amplitude in the frequency range 1.5-8kHz, lower TEOAE amplitude, and slightly decreased TEOAE suppression were measured in tinnitus subjects compared to non-tinnitus controls. In particular, 74% of tinnitus subjects exhibited abnormal DPOAEs, 13% had abnormal TEOAEs, whereas abnormal TEOAE suppression was found in 9% of patients.
Overall, the present work revealed the presence of abnormal OAEs, in particular at higher frequencies, in tinnitus subjects with normal hearing sensitivity. A minor (i.e., sub-clinical) outer hair cell dysfunction, particularly in high-frequency cochlear regions, might thus be assumed in normal hearing tinnitus subjects. In order to better put in light the possible role played by outer hair cells in low-frequency cochlear regions, or by the cochlear efferent system, additional analyses would be needed.
本研究旨在探讨在听力正常的耳朵出现耳鸣时，外毛细胞和耳蜗传出系统功能可能发挥的作用。采用了多参数方法，包括记录和分析一组耳声发射（OAEs）：畸变产物（DPOAEs）、瞬态诱发（TEOAEs）以及在对侧声刺激（CAS）存在时的传出介导的TEOAEs抑制。
54名听力敏感度正常的受试者参与了该研究。其中23名患有慢性主观性耳鸣，而31名没有耳鸣，作为对照受试者。在0.5 - 8kHz频率范围内，使用频率比为1.22、强度为65和55dB SPL的诱发音测量DPOAEs。采用“线性”方案，在有无两种不同强度的CAS情况下，使用峰值声压级为60dB的短声记录TEOAEs。分析DPOAE幅度、TEOAE幅度和TEOAE抑制作为相关参数。
与无耳鸣对照组相比，耳鸣受试者在1.5 - 8kHz频率范围内的DPOAE幅度显著降低，TEOAE幅度较低，TEOAE抑制略有下降。特别是，74%的耳鸣受试者表现出异常的DPOAEs，13%有异常的TEOAEs，而9%的患者存在异常的TEOAE抑制。
总体而言，本研究揭示了听力敏感度正常的耳鸣受试者中存在异常的耳声发射，尤其是在较高频率。因此，可以推测在听力正常的耳鸣受试者中存在轻微（即亚临床）的外毛细胞功能障碍，特别是在高频耳蜗区域。为了更好地阐明外毛细胞在低频耳蜗区域或耳蜗传出系统可能发挥的作用，还需要进行额外的分析。
