The Pathogenetic Mechanism Of Cortical Deficit In Children With Strabismic Amblyopia And Anisometropic Amblyopia Detected By Functional MRI

Object To detecte the pathogenetic mechanism of cortical deficit in children with strabismic amblyopia and anisometropic amblyopia by blood oxygenation level dependent—unctional magnetic resonance imaging(BOLD-fMRI).To investigate the active dependence of visual cortex on the spatial frequencies of visual signals in human strabismic and anisometropic amblyopia.To analyze the correlation between the decreased cortical activation and visual acuity.Methods BOLD-fMRI technique on 1.5T SIMENS SONATA MRI was used.Blocks designation mode was used.The visual stimulus is a black-and-white checkerboard with the spatial frequencies of 0.5,1.0,2.0 cycle/degree and the temporal frequency 8 Hz.The baseline stimulus is a white cross-line at the center of the screen with black background.Subjects included 24 strabismic amblyopes,25 anisometropic amblyopes and 25 normal subjects(5 to 13 years old).The functional image data was acquired with a echo-planar imaging(EPI)sequence.Anatomical reference images were collected using a three-dimensional,Tl -weighted FSPGR imaging sequence.All data obtained were analyzed offline with SPM2 software.The threshold value was set to 0.05.During data processing,motion correction and three-dimensional smooth were used.Time-signal intensity curves and functional images could be obtained.After Talairach coordinating function images,The analysis included:①Goup effects analysis of cortex activation area was performed between the amblyopic eyes(control's left eyes) and the fellow eyes(control's right eyes)in the strabismic amblyopes,anisometropic amblyopes and normal subjects.②Paired t-tests of cortex activation area was performed in the normal controls with left eye stimulation,right eye stimulation.③Two-sample t-tests were used to perform intergroup contrast between the amblyopic eyes,the fellow eyes of the strabismic amblyopia and controls.④Two-sample t-tests were used to perform intergroup contrast between the amblyopic eyes,the fellow eyes of the anisometropic amblyopia and controls.⑤Group effeets analysis of cortex activation area of the amblyopic eyes and the fellow eyes was performed between the strabismic amblyopes and anisometropic amblyopes.⑥In the different spatial frequencies(0.5,1.0,2.0 c/d),ONE WAY-ANOVA were used to perform intergroup contrast between the amblyopic eyes,the fellow eyes of the two type amblyopia and controls.⑦Line-correlation were used to perform correlation between the decreased cortical activation and visual acuity.Results①First,The most obvious activation area was primary visual cortex included upper lip and lower lip of calacarine fissure(BA17)in the normal controls with monoeular stimulation,such as cuneus,lingual gyrus;Second,the BA18,19 area was activated include middle gyrus of occipital lobe,fusiform gyrus and inferior temporal gyrus et al;②The dominant cerebral hemisphere of visual cortex activation was the right side in the normal controls with monocular stimulation;③The spatial extent and intensity of the visual cortex activation in the visual cortex of BA17,18, 19 was obviously decreased with the amblyopic eye in strabismic amblyopia than in normal controls;the fellow eye mainly decreased in the visual cortex of BA19;the amblyopic eye was obviously decreased in the visual cortex of BA17,18 than the fellow eye,no obvious different in the BA19;④The spatial extent and intensity of the visual cortex activation in the visual cortex of BA18,19 was obviously decreased with the amblyopic eye in anisometropic amblyopia than in normal controls;the fellow eye mainly decreased in the visual cortex of BA18;the amblyopic eye was obviously decreased in the visual cortex of BA17,18,19 than the fellow eye,no obvious different in the BA17;⑤The spatial extent and intensity of the visual cortex activation in the visual cortex of BA17,18 was obviously decreased with the amblyopic eye in strabismic amblyopia than in anisometropic amblyopia,the fellow eye mainly decreased in the visual cortex of BA18,19;⑥The amblyopic eye of strabismic amblyopia was more suppressed at spatial frequencies(1.0,2.0 c/d) than in normal controls(P＜0.05),the fellow eye at higer spatial frequencies(2.0 c/d) (P＜0.05);no obvious different between the amblyopic eye and the fellow eye at all spatial frequencies(P＞0.05);⑦The amblyopic eye of anisometropic amblyopia was more suppressed at all spatial frequencies(0.5,1.0,2.0 c/d) than in normal controls (P＜0.01),the fellow eye at higher spatial frequencies(2.0 c/d)(P＜0.05);the amblyoPic eye was more suppressed at all spatial frequencies(0.5,1.0,2.0 c/d) than the fellow eye(P＜0.05);⑧There is no linear correlation between the function lesion of cortical activation and visual acuity.Conclusion①visual contex were not only located at striate cortex,but also at prestriate cortex,inferior temporal gyrus and posterior lobe,et al;②The spatial extent and intensity of the visual cortex activation in the visual cortex of BA17,18,19 was decreased in strabismic amblyopia and anisometropic amblyopia than in normal controls;while the fellow eye was also abnormal;③There had obvious different between the strabismic and anisometropic amblyopia;④There had the active dependence of visual cortex on the spatial frequencies of visual signals in human strabismic and anisometropic amblyopia;⑤There is no linear correlation between the function lesion of cortical activation and visual acuity.