Grégoire Anaïs, Deggouj Naïma, Dricot Laurence, Decat Monique, Kupers Ron
Department of ENT, Cliniques Universitaires Saint-Luc, Brussels, Belgium.
Institute of NeuroScience (IoNS), UCLouvain, Brussels, Belgium.
Front Neurosci. 2022 Mar 28;16:850245. doi: 10.3389/fnins.2022.850245. eCollection 2022.
Neuroplasticity following deafness has been widely demonstrated in both humans and animals, but the anatomical substrate of these changes is not yet clear in human brain. However, it is of high importance since hearing loss is a growing problem due to aging population. Moreover, knowing these brain changes could help to understand some disappointing results with cochlear implant, and therefore could improve hearing rehabilitation. A systematic review and a coordinate-based meta-analysis were realized about the morphological brain changes highlighted by MRI in severe to profound hearing loss, congenital and acquired before or after language onset. 25 papers were included in our review, concerning more than 400 deaf subjects, most of them presenting prelingual deafness. The most consistent finding is a volumetric decrease in gray matter around bilateral auditory cortex. This change was confirmed by the coordinate-based meta-analysis which shows three converging clusters in this region. The visual areas of deaf children is also significantly impacted, with a decrease of the volume of both gray and white matters. Finally, deafness is responsible of a gray matter increase within the cerebellum, especially at the right side. These results are largely discussed and compared with those from deaf animal models and blind humans, which demonstrate for example a much more consistent gray matter decrease along their respective primary sensory pathway. In human deafness, a lot of other factors than deafness could interact on the brain plasticity. One of the most important is the use of sign language and its age of acquisition, which induce among others changes within the hand motor region and the visual cortex. But other confounding factors exist which have been too little considered in the current literature, such as the etiology of the hearing impairment, the speech-reading ability, the hearing aid use, the frequent associated vestibular dysfunction or neurocognitive impairment. Another important weakness highlighted by this review concern the lack of papers about postlingual deafness, whereas it represents most of the deaf population. Further studies are needed to better understand these issues, and finally try to improve deafness rehabilitation.
耳聋后的神经可塑性在人类和动物中均已得到广泛证实,但这些变化在人类大脑中的解剖学基础尚不清楚。然而,这一点至关重要,因为由于人口老龄化,听力损失问题日益严重。此外,了解这些大脑变化有助于理解人工耳蜗植入出现的一些令人失望的结果,从而改善听力康复。我们针对严重至极重度听力损失(包括先天性和语言发育前后获得性听力损失)患者,对MRI所显示的大脑形态变化进行了系统综述和基于坐标的荟萃分析。我们的综述纳入了25篇论文,涉及400多名耳聋受试者,其中大多数为语前聋患者。最一致的发现是双侧听觉皮层周围灰质体积减小。基于坐标的荟萃分析证实了这一变化,该分析显示该区域有三个汇聚簇。耳聋儿童的视觉区域也受到显著影响,灰质和白质体积均减小。最后,耳聋导致小脑内灰质增加,尤其是右侧。我们对这些结果进行了广泛讨论,并与耳聋动物模型和盲人的结果进行了比较,例如后者显示沿其各自的主要感觉通路灰质减少更为一致。在人类耳聋中,许多因素而非耳聋本身可能会影响大脑可塑性。其中最重要的因素之一是手语的使用及其习得年龄,这会导致手部运动区域和视觉皮层等部位发生变化。但其他混杂因素也存在,而当前文献对此考虑过少,如听力障碍的病因、唇读能力、助听器使用情况、频繁伴发的前庭功能障碍或神经认知障碍。本综述突出的另一个重要不足是缺乏关于语后聋的论文,而语后聋占大多数耳聋人群。需要进一步研究以更好地理解这些问题,并最终尝试改善耳聋康复。