长期单侧耳聋患者大脑皮层功能MRI的重组

Functional magnetic resonance imaging in patients with long-term unilateral hearing loss

目的研究长期单侧耳聋患者听觉皮层及相应脑区的功能活动，判断可能存在的功能重组。方法收集2008年6月至2009年12月东南大学附属中大医院单侧重度耳聋患者23例（左、右侧聋各为15和8例）；匹配正常对照组15名。用健侧耳听觉任务的fMRI观察单（健）耳听觉任务下初级听觉皮层（PAC）激活体素的偏侧性指数（LI）及其他相关脑区的功能活动。结果3例左耳聋及1名对照头动超过限度，数据舍去。对照组分析图表现为对侧听觉皮层激活优势，L1分别为97、100。单侧耳聋组分析图显示两侧PAC激活较为均衡，对侧优势减弱，Ⅱ分别为21．9、52．4。与正常对照组比较在PAC以外，单侧聋人还表现左侧额叶、双侧顶下小叶及左侧枕叶／楔前叶等脑区的激活增强，但也存在左侧颞上回的激活减弱。结论长期单侧耳聋患者听觉皮层对侧优势的减弱和其他脑区的激活可提示两侧半球交叉抑制的减弱以及脑兴奋的泛化，可能是大脑适应性功能重组的表现；而左侧颞上回的活动减弱可能与其语言理解能力的下降有关。

Objective To evaluate the potential functional reorganization by functional magnetic resonance imaging （ MRI ） to measure the brain activation in responses to stimulation to healthy ears in patients with long-term unilateral hearing loss （UHL）. Methods From June 2008 to December 2009, 23 patients with serious UHL （15 left, 8 right） were recruited along with 15 matched normal hearing subjects. Laterality index （LI） for activated voxel in primary auditory cortex （PAC） was calculated. And the activations outside auditory cortex were also evaluated. Results The data were discarded in 3 patients with left-ear UHL and 1 normal subject because of head motion. All control subjects showed contralateral dominant activation of PAC in group analysis. However, the group data of UHL patients showed that the activation was more symmetrical and the contralateral dominance diminished versus the control group. As compared with normal subjects outside PAC, heightened activation in left prefrontal cortex, bilateral inferior parietal lobule and left occipital/precuneus was found in UHL patients while reduced activation in left superior temporal gyrus was also found. Conclusion The diminished contralateral dominance in PAC and heightened activation in non-anditory region suggest the reduction of interhemispheral inhibition and general increase in brain excitation in long-term UHL patients potentially occur as a result of functional reorganization adaptive to UHL. However, the reduced activation in superior temporal gyrus may be correlated with the deterioration of speech perception in these patients.