The Application Of Resting-state FMRI In Patients With Non-lesional Epilepsy Based On ALFF And Graph Theory

Objective:By analyzing the amplitude of brain neurons' spontaneous activity and brain network spatial topological properties with the use of amplitude of low-frequency fluctuation(ALFF)and complex networks analysis based on the graph theory,in order to improve the understanding of the pathophysiological mechanism of non-lesional epilepsy patients.Methods:42 NLE patients and 42 age-and gender-matched healthy volunteers were enrolled and underwent rs-fMRI by 3.0T MR scanner.The data processing includes:(1)Data preprocessing was performed using data processing assistant for resting-state fMRI(DPARSF).The values of ALFF and fALFF in the frequency band of 0.01~0.08 Hz and the values of ALFF in the slow-4(0.027~0.073Hz)and slow-5(0.01~0.027Hz)bands were calculated with REST software.A two-sample t test was performed using SPM8 to observe the differences of ALFF and fALFF between NLE and HC groups;a mixed-design ANOVA was performed using SPM8 to analyze the effects of group(NLE and HC),frequency band(slow-4 and slow-5)and interaction effects of both group and frequency band,and then to compare the ALFF values between NLE and HC groups in slow-4 and slow-5 band,respectively.(2)Using Gretna and Brain Net Viewer software,automated anatomic markers(AAL)template was defined and extracted,then a functional connective network was built,and every topology parameters under different network sparse degree index were calculated and used for two sample t-test between two groups(P<0.05).Results:(1)Compared with HC group,NLE patients have increased ALFF in the left middle temporal gyrus,and decreased ALFF in the left anterior cingulate gyrus,the left inferior orbital frontal gyrus,the right cerebellum posterior lobe,the right insula and the right superior parietal lobule;NLE patients have increased fALFF in bilateral middle temporal gyrus and the left angular gyrus,and decreased fALFF in the right precuneus and the right inferior parietal lobule(P<0.05,corrected by AlphaSim).The results between the main effect of the sub-bands ALFF and the classical band ALFF are basically consistent.Compared with the slow-5 band,slow-4 band had increased ALFF value in bilateral brain stem,the right cerebellum inferior lobe,the right cerebellum posterior lobe,left superior temporal gyrus and left inferior temporal gyrus,and reduced ALFF value in right rectus,right orbital and trigeminal inferior frontal gyrus,right lingual,right inferior occipital gyrus,left superior frontal gyrus,left middle temporal gyrus,left superior temporal gyrus,left cuneus and bilateral precuneus(P<0.05,corrected by AlphaSim).(2)Complex network analysis based on graph theory shows that both NLE and HC groups have "small world" properties.? and ? decrease with increased sparsity,? is larger than 1 and ? is close to 1.But the differences of ? and ? value between the two groups were not statistically significant.In the threshold range,only clustering coefficient(Cp)of NLE group was significantly lower than HC group,the difference was statistically significant.In addition,the difference of the area under the curve of path length(Lp)?global efficiency(Eglob),local efficiency(Eloc)and other global indicators between two groups was not statistically significant.The results showed that the nodal efficiency of bilateral dorsolateral frontal gyrus,bilateral medial superior frontal gyrus,left middle frontal gyrus,bilateral inferior parietal lobule were reduced,and the nodal efficiency of left angular gyrus was increased.The degree of bilateral dorsolateral frontal gyrus,bilateral medial superior frontal gyrus,left middle frontal gyrus were decreased,and the degree of the left angular gyrus and left temporal pole were increased(P<0.05).Conclusions :(1)The areas of increased ALFF and fALFF in NLE patients were mainly located in the temporal lobe,which was closely related to the origin and transmission of epileptic discharges.The areas of reduced ALFF and fALFF were mainly located in DMN-related brain regions,suggesting that the normal function of DMN was destroyed or inhibited.Compared with ALFF,fALFF can inhibit the noise besides ventricle and brain pool,and has a higher accuracy of detecting abnormal brain activity.NLE patients have widespread abnormal neural oscillations,a portion of which are dependent on specific frequency bands.Slow-4 and slow-5 band can detect brain regions of abnormal brain activity in NLE patients complementally.(2)NLE patients still have the small world network property,but its internal characteristics have changed,the clustering coefficient decreased significantly,the path length increased slightly,the ? decreased slightly and the ? increased slightly.These abnormal indicators suggest the dysfunction of the small-world network of patients withepilepsy,and decrease of the ability to local information processing.Abnormalities of multiple brain areas in nodal efficiency and nodal degree may be related to the clinical symptoms of epilepsy patients.