Objective: To explore the neuromechanism of trans-auricular vagus nerve stimulation (taVNS) for treatment-resistant depression(TRD) based on functional brain network.
Methods: Twenty-eight patients with TRD were recruited from the psychiatric clinic or by the advertisement. The patients were treated by taVNS (5 Hz/20 Hz, 4-8 mA) at the auricular concha for 30 min, twice daily for 8 weeks. The symptom severity was assessed by 17-Item Hamilton Rating Scale for Depression (HAMD-17, ranging from 0 to 54 points, higher score indicates more severe conditions). Resting state fMRI data of the brain were collected to analyze changes of the regional homogeneity (ReHo), amplitude of low frequency fluctuation (ALFF) and resting state functional connectivity (rs-FC) before and after 8 weeks' taVNS by using DPARSF toolkit and the correlation between the rs-FC and clinical scale score was analyzed to assess the related brain mechanisms.
Results: Twenty-four patients finished the clinical study, and 23 patients finished the fMRI tests. After the treatment, the average score of HAMD-17 was significantly decreased (P<0.01), with the reduction rate being 66.95%; the ALFF and ReHo values of the right insula and putamen, the ReHo values of the right caudate nucleus and thalamus, as well as the rs-FC values of the right insula, left superior frontal gyrus and middle frontal gyrus were all significantly decreased (P<0.05). The reduced ReHo value in the right insular lobe was negatively correlated with the HAMD score reduction (P=0.001, r=-0.633). The rs-FC values of the right insula lobe and the left superior frontal gyrus were significantly negatively correlated with the reduced HAMD score(P=0.012, r=-0.512).
Conclusion: TaVNS significantly relieves the symptoms of TRD patients, which may be related to its functions in regulating functional changes of the right insular and the left frontal gyrus network, and the limbic area and basal ganglia.
目的：探索经皮耳穴迷走神经刺激(taVNS)治疗难治性抑郁症(TRD)的脑功能网络机制。方法：28例TRD患者均给予8周taVNS耳甲部治疗，采集治疗前后汉密尔顿抑郁(HAMD-17)量表评分和fMRI静息态脑功能磁共振数据进行统计分析。结果：24例患者完成了临床研究，其中23例完成脑fMRI试验。患者治疗后HAMD-17评分降低(P<0.01), 平均减分率为66.95%，其中11例痊愈，7例显著进步，5例进步，1例无效，总有效率为95.83%。8周治疗后，TRD患者的右侧岛叶、壳核的低频振幅(ALFF)和局部一致性(ReHo)值，前扣带回、右侧尾状核、右侧丘脑ReHo值，右侧岛叶与左侧额上回、额中回静息态功能连接(rs-FC)值均低于治疗前(P<0.05)。TRD患者治疗前后ALFF差异脑区与HAMD-17减分率无相关关系。右侧岛叶ReHo差值与HAMD-17减分率呈显著负相关(P=0.001，r=-0.633)；右侧岛叶与左侧额上回的rs-FC差值与HAMD-17减分率呈显著负相关(P=0.012, r=-0.512)。结论：右脑岛-左额上回功能变化可能是taVNS治疗TRD的脑网络机制，taVNS还对基底节及边缘叶脑区产生了效应。.
Keywords: Basal ganglia; Insular-prefrontal functional network; Resting-state functional MRI; Trans-auricular point vagus nerve stimulation (taVNS); Treatment-resistant depression.