Magnetic seizure therapy modulates default mode network fluctuations of major depressive disorder / 中华行为医学与脑科学杂志

Objective To observe the change of functional connectivity(FC) between default mode network (DMN) and the other brain regions in patients with depression before and after magnetic seizure therapy(MST),and explore the role of DMN in therapeutic mechanism of MST.Methods Fifteen patients with depression who met the criteria of enrollment underwent rs-fMRI scanning before and after the MST treatmerts.As a very important region of DMN,the posterior cingulate cortex(PCC) was selected as the region of interest(ROI)to make the functional connectivity analysis with other brain regions,then the differences in FC before and after MST treatments were tested.The correlation of FC index changes with the score changes of HAMD-17 and five factors of HAMD-17 was analyzed after MST treatments.Results A comparison of the differences in DMN before and after treatments showed that the connection between left PCC and bilateral medial temporal lobe connectivity decreased significantly (left:MNI:x,y,z =-66,-39,-15,right:MNI:x,y,z =69,-30,-6) (P＜ 0.05).The connection between left PCC with left cerebellum (MNI:x,y,z =-33,-42,-42) and left occipital lobe(MNI:x,y,z=0,-84,24)significantly increased(P＜0.05).The changes of sleep factor of HAMD-17 were positively correlated with the functional connectivity changes of bilateral medial temporal lobe (left:r=0.670,P=0.006;right:r=0.570,P=0.026),but negatively correlated with the functional connectivity changes of the left cerebellum (r=-0.543,P=0.037).Conclusion MST can play an antidepressant role by regulating DMN functional connection of depressive patients and it may be a neuromodulation mechanism of MST in the treatment of depression.

Electric field simulation and analysis of modified electroconvulsive therapy and magnetic seizure therapy in a realistic human head model / 生物医学工程学杂志

Modified electroconvulsive therapy (MECT) and magnetic seizure therapy (MST) are effective treatments for severe major depression. MECT has better efficacy in the treatment than MST, but it has cognitive and memorial side effects while MST does not. To study the causes of these different outcomes, this study contrasted the electric filed strength and spatial distribution induced by MECT and MST in a realistic human head model. Electric field strength induced by MECT and MST are simulated by the finite element method, which was based on a realistic human head model obtained by magnetic resonance imaging. The electrode configuration of MECT is standard bifrontal stimulation configuration, and the coil configuration of MST is circular. Maps of the ratio of the electric field strength to neural activation threshold are obtained to evaluate the stimulation strength and stimulation focality in brain regions. The stimulation strength induced by MECT is stronger than MST, and the activated region is wider. MECT stimulation strength in gray matter is 17.817 times of that by MST, and MECT stimulation strength in white matter is 23.312 times of that by MST. As well, MECT stimulation strength in hippocampi is 35.162 times of that by MST. More than 99.999% of the brain volume is stimulated at suprathreshold by MECT. However, MST activated only 0.700% of the brain volume. The stimulation strength induced by MECT is stronger than MST, and the activated region is wider may be the reason that MECT has better effectiveness. Nevertheless, the stronger stimulation strength in hippocampi induced by MECT may be the reason that MECT is more likely to give rise to side effects. Based on the results of this study, it is expected that a more accurate clinical quantitative treatment scheme should be studied in the future.

Treatment of Late-Life Depression by Brain Stimulation Techniques

Due to the low response rate of antidepressant treatment in late-life depression, brain stimulation techniques should be considered when treating elderly patients. Electroconvulsive therapy (ECT) is one of the most frequently used brain stimulation techniques, and shows favorable outcome and acceptable tolerability in the treatment of late-life depression. Hemodynamic change and cognitive impairment are common side effects of ECT, which are transient in most cases. Since cognitive impairment can lead to treatment non-compliance, it should be minimized by controlling electrode position, pulse-width, treatment frequency, etc. Because ECT is followed by rapid cardiovascular change, risk factors should be evaluated and managed properly. Transcranial magnetic stimulation (TMS) and magnetic seizure therapy (MST) are also shown to be effective in treating depression, with less cognitive impairment. However, further research is needed to establish their efficacy in late-life depression.