The Correlation Between Mri Image Of Tumors Around Optic Chiasm And Visual Function

Background and PurposeTumors around optic chiasm can oppress optic nerve,optic chiasm,and optic tract,thus leading to decreased vision and visual field defects.In this research these tumors were checked in image-clinic-laboratory examination to study the relationship between their MRI presentations and vision,visual field and evoked potential in order to offer evidences for clinical diagnosis and further researches.Materials and methods100 patients had tumors around optic chiasma which were proved by operations and pathology in the people,hospotal of Henan province from September 2007 to December 2008.They were examined by hypsifield MRI(Siemens 1.0T or 3.0T MR scanning unit),visual field,vision and visual evoked potential(VEP).Optic chiasma was routinely scanned in coronal,sagittal,axial T1WI and coronal,axial T2WI. Scanning parameters:slice thickness/slice distance:3mm/0mm,FOV 210mm×210mm,matrix 256×256;collection twice.All MRI images were read by two professional staffs double-blindly.ⅰClassification according to localization and displacement that optic chiasma was oppressed:the team could be divided into three types.Type A:the tumor oppressed the optic chiasma from the bottom,made it up;Type A1:only oppressed the optic chiasma,Type A2:oppressed the optic chiasma from front or back at the same time. Type B:the tumor oppressed the optic chiasma from anodic,made it down;Type B1:only oppressed the optic chiasma,Type B2:oppressed the optic chiasma from front or back at the same time.Type C:the optic chiasma was embedded by tumor and unclear.ⅱvisual field change:the visual field defects had 7 types:normal visual field,half blind-spot,one quadrant defect,bitemporal hemianopia,bitemporal hemianopia beyond central line and expand to upper and/or subtus quadrant of nose,concentric contraction,ablepsia totalis.It had 5 levels according to the degree of visual field defects:less than 1/2 quadrant,1 quadrant,2 quadrant,3 quadrant,4 quadrant.ⅲVisual evoked potential change:VEP had 5 grades:gradeⅠ-latency period was normal,waveform was clear and smoothing,Ⅱ- latency period was normal,wave amplitude was cut down,or wave amplitude was normal but latency period was longer,Ⅲ- latency period was longer,wave amplitude was less than normal,Ⅳ-waveform was abnormal,latency period was longer,waveform was hard to recognize and analyze,Ⅴ-reaction was disappear and waveform was straight.ⅳStatistical analysis:experimental data was handled with SPSS 13.0 software in rank sum test.Test of significance was considered as a=0.05.ResultsⅠRelationship between the bionomics of tumor around optic chiasma and visual functionⅰRelationship between the size of tumor around optic chiasma and the change of visual functionPatients with tumors around optic chiasm whose diameter was less than 30mm had lower degree of impaired vision,smaller visual field demage extent and lower stage of visual evoked potential changes than those patients with tumors around optic chiasm whose diameter was more than 30mm.The size of tumors around optic chiasma and the descendent degree of visual acuity,visual field damage extent and stage number of visual evoked potential change have statistically difference(P＜0.05).ⅱRelationship between the internal structure of tumors around optic chiasma and the change of visual functionIn all patients,the internal structure of tumors around optic chiasma according to the descendent degree of visual acuity,visual field damage extent and stage number of visual evoked potential change were spina bifida cystica(most slightly),spina bifida cystica-kernel,kernel(most severe).There were statistical difference among the three groups.ⅲRelationship between the pathological type of tumor around optic chiasma and the change of visual functionThis group contained hypophysoma,craniopharyngioma,durosarcoma,chord blastoma,neurogliocytoma,germ cell tumor,tuberculoma,Rathke's cyst,hem ngioblastoma.There were no relationship between the character of tumors around optic chiasma and the descendent degree of visual acuity,visual field damage extent and stage number of visual evoked potential change(P＞0.05).ⅡRelationship between the abnormal shape,malposition and the visual functionⅰRelationship between the oppressed location,dislocated direction of optic chiasma and the descendent degree of visual acuityIn this group,3cases(6 eyes) was Type A1,light perception～0.1 in 2 eyes,0.2～1.0 in 3 eyes,54 cases(108 eyes) was Type A2,light perception～0.1 in 19 eyes, 0.2～1.0 in 75 eyes,visual acuity exceeding 1.0 in 14 eyes.3case(6 eyes) was Type B1,visual acuity exceeding 1.0 in 3eyes,0.5～1.0 in 3 eyes,15cases(30 eyes) was Type B2,light perception～0.1 in 4 eyes,0.2～1.0 in 23 eyes,visual acuity exceeding 1.0 in 3 eyes.25cases(50 eyes) was Type C,no light perception in 3 eyes,light perception～0.1 in 18 eyes,0.2～1.0 in 27 eyes,visual acuity exceeding 1.0 in 2 eyes. The descendent degree of visual acuity:Type C＞Type A＞Type B;Type A2＞Type A1,Type B2＞Type B1.There were statistical difference among the three groups(P＜0.05).ⅱRelationship between the oppressed location,dislocated direction of optic chiasma and the visual field damageIn this group,Type A1 was normal visual field in 3 eyes,abnormal visual field in upper temporal quadrant in 3 eyes,inferior temporal quadrant in 1 eye,inferior nasal quadrant in 1 eye and upper nasal quadrant in 0 eye.Type A2 was abnormal visual field in upper temporal quadrant in 105 eyes,inferior temporal quadrant in 95 eyes, inferior nasal quadrant in 55 eyes and upper nasal quadrant in 4 eyes.Type B1 was normal visual field in 4 eye,abnormal visual field in upper temporal quadrant in 1 eye, inferior temporal quadrant in 1 eye,inferior nasal quadrant in 1 eye and upper nasal quadrant in 1 eye.Type B2 was abnormal visual field in upper temporal quadrant in 13 eyes,inferior temporal quadrant in 25 eyes,inferior nasal quadrant in 3 eyes and upper nasal quadrant in 1 eye.Type C was normal visual field in 0 eye,abnormal visual field in upper temporal quadrant in 45 eyes,inferior temporal quadrant in 34 eyes,inferior nasal quadrant in 24 eyes,upper nasal quadrant in 9 eyes.The visual field damage degree:Type C＞Type A＞Type B,Type A2＞Type A1,Type B2＞Type B1.There were statistical difference among the three groups(P＜0.05).ⅲRelationship between the oppression of optic chiasma and visual evoked potentialType A1 was VEP＜gradeⅢin 5 eyes,VEP≥gradeⅢin 1 eye,Type A2was VEP＜gradeⅢin 53 eyes,VEP≥gradeⅢin 55 eyes.Type B1 was VEP＜gradeⅢin 6 eyes,Type B2 was VEP＜gradeⅢin 24 eyes,VEP≥gradeⅢin 6 eyes.Type C was VEP＜gradeⅢin 17 eyes,VEP≥gradeⅢin 33 eyes.The abnormal degree of visual evoked potential:Type C＞Type A＞Type B,Type A2＞Type A1,Type B2＞Type B1.There were statistical difference among the three groups(P＜0.05 ).ConclusionsⅰThe size and internal structure of tumors around optic chiasma have correlation with visual function damage(P＜0.05).ⅱThe character of tumors around optic chiasma have no correlation with visual function damage(P＞0.05).ⅲWhen optic chiasma was oppressed and moved down,the visual function damage was the lightest.It was more serious when optic chiasma was oppressed and moved up,and most serious when optic chiasma was embedded and unclear(P＜0.05).ⅳWhen tumors oppressed optic chiasma from the anodic and made it down,the subsequence(from high to low) that visual field defect happened was inferior temporal quadrant,upper temporal quadrant,inferior nasal quadrant,upper nasal quadrant,when optic chiasma was embedded by tumors or unclear and the tumors oppressed optic chiasma and made it up,the subsequence was upper temporal quadrant,inferior temporal quadrant,inferior nasal quadrant,upper nasal quadrant.ⅴThe most common type of visual field defect was bitemporal hemianopia beyond central line and expanding to upper nasal quadrant and inferior nasal quadrant.