老年人大脑听觉皮质功能区老化的神经磁学研究

Neural magnetologic research on the functional aging of cerebral auditory cortex in elderly people

目的:分析老年人随年龄增加出现的大脑听觉皮质老化的发生发展规律,为老年聋的防治提供依据。方法:所有受试者为2002-01/2005-01在河北省人民医院耳鼻咽喉科门诊就诊者。以306通道全头型脑磁图仪分别测试青年组(18～28岁)30例、老年前期组(45～59岁)35名、老年期组(60～80岁)32名健康受试者0.5,1,2,4,6kHz纯音诱发的双侧大脑半球听觉皮质脑磁场M100,并与其MRI解剖影像信息叠加整合,得到大脑听觉皮质磁源性影像。分析比较不同年龄组各刺激频率纯音所诱发M100的潜伏期、波幅及其等电流偶极在X、Y、Z坐标轴的三维定位。结果:97名健康人均完成全部测试,进入结果分析。①老年前期组和老年期组与青年对照组比较,其纯音听力在所有测试频率均随年龄增加显著逐渐下降(P<0.01);M100的潜伏期随年龄增加逐渐延长,波幅逐渐降低。②老年期组在各刺激声频率诱发的M100潜伏期和波幅均较老年前期组和青年组出现了有统计学意义的显著延长或降低;M100的等电流偶极位置双侧大脑半球听觉皮质均在2,6kHz刺激声发生向内、后、下方向的位移或偏离,在4kHz均发生向内、后、上的位移或偏离;等电流偶极的位置分布亦随年龄增加而逐渐分散。结论:老年人的大脑听觉皮质随年龄增加而发生的老化主要表现为大脑听觉皮质在激活的时间、程度和空间位置的重组,探寻纠正和改善这种重组发生的方法可能成为未来有希望预防和治疗老年人年龄相关性听力下降发生和发展的一种有效途径。

AIM： To analyze the occurrence and progress rules of aging auditory cortex in elderly people with increased age so as to provide theoretic basis for the prevention and treatment of presbyacusis. METHODS： All the subjects were selected from the outpatients in the Department of ENT of Hebei Provincial People＇s Hospital from January 2002 to January 2005. The auditory cortex magnetic field M100 of hilateral hemispheres evoked by 0.5 kHz, 1 kHz, 2 kHz, 4 kHz, 6 kHz pure tones were examined with 306-channel whole-head neural magnetometer in 30 cases of young group （18-28 years）, 35 cases of the pre-senile group （45-59 years）, 32 cases of the senile group （60-80 years） and 32 healthy subjects, which was combined with the anatomic structural data of magnetic resonance imaging （MRI） to obtain the magnetic source imaging （MSI） of cerebral auditory cortex. The latencies, amplitudes and the threedimensional localizations of equivalent current dipole （ECD） on X, Y, Z coordinate axis of pure tone induced M100 with different stimulating frequency were analyzed and compared respectively among three age groups. RESULTS： A total of 97 healthy subjects were tested and involved in the analysis of results.①The pure-tone hearing levels at all testing frequencies＇ were significantly decreased with the age increasing in pre-senile and senile groups than that in the young control group （P 〈 0.01）; And the latencies and the amplitudes of M100 were longer and smaller with the increased age. ②The latencies and amplitudes of M100 induced by stimulus audible frequency were significantly prolonged and decreased in senile group than those in the young and pre-senile groups, which had a statistical significance; The locations of M100 ECD evoked by 2 kHz and 6 kHz pure tones significantly shifted to medial, posterior and inferior parts or deviated, and the location of M100 ECD evoked by 4 kHz pure tone significantly shifted to medial, posterior and superior parts or deviated; The distribution of ECD location gradually dispersed with the increased age. CONCLUSION： The aging of cerebral auditory cortex in elderly people with the increased age mainly presents as the reorganizations of cerebral auditory cortex in activated latency, extent and space, h may be a potential interventional strategy for the prevention and treatment of presbyacusis to probe into, rectify and improve these cortical reorganizations.