大前庭导水管畸形3D-FLAIR表现及临床应用价值

The presentation and its clinical diagnostic value of 3D-FLAIR in large vestibular aqueduct

目的探讨大前庭导水管畸形(LVA)患耳的三维液体衰减反转恢复序列(3D-FLAIR)表现及临床应用价值。方法分析行HRCT和MRI[三维可变反转角继发高分辨率快速自旋回波(3D-SPACE)和3D-FLAIR]检查经临床诊断为LVA的患者328例(649耳)影像学资料,根据患耳淋巴管(ED)和内淋巴囊(ES)内在3D-FLAIR序列高信号范围将其分为3型:Ⅰ型:在3D-FLAIR无高信号;Ⅱ型:在3D-FLAIR显示部分高信号;Ⅲ型:在3D-FLAIR呈完全高信号。计算3D-FLAIR内耳及ED和ES内高信号发生率、LVA患耳ED和ES在3D-SPACE和3D-FLAIR完整显示率。利用卡方检验3D-SPACE和3D-FLAIR患耳对ED和ES完整显示率、3D-SPACE和3D-SPACE+3D-FLAIR诊断正确率间差异性。并分析LVA患耳在3D-SPACE检查中存在假阴性的原因。结果328例LVA(649耳)中患耳的内耳及ED和ES内出现高信号比率分别为49.0%、91.7%。内耳及ED和ES内在3D-FLAIR高信号的范围及强度不一。其中Ⅰ型、Ⅱ型、Ⅲ型分别为54耳(8.3%)、570耳(87.8%)、25耳(3.9%)。3D-SPACE和3D-FLAIR对患耳的ED和ES完整显示率分别为93.7%(608/649)、4.2%(27/649),两者间比较差异有统计学意义(χ^(2)=1040.7,P<0.05)。3D-SPACE和3D-SPACE+3D-FLAIR正确率分别为95.7%(621/649)和100%(649/649),两组间比较差异有统计学意义(χ^(2)=28.6,P<0.05)。对3D-SPACE假阴性19例(28耳)LVA(Ⅱ型25耳、Ⅲ型3耳)分析如下:2耳患侧前庭导水管在HRCT上显示明显扩张,在3D-SPACE患侧ED和ES内信号较低难以显示,在3D-FLAIR可清晰显示;另26耳LVA患侧前庭导水管扩张程度较轻或无扩张,其患侧ED和ES骨内外部分扩张程度均较轻且其远端内信号复杂,其在3D-SPACE难以显示,而在3D-FLAIR呈高信号易于显示。结论LVA患侧内耳及ED和ES内信号异常可能是该病MRI表现特征之一;3D-FLAIR不适于单独应用于LVA诊断,其与3D-SPACE联合有助于提高部分LVA患耳的诊断。

Objective To explore the presentations of the 3-dimensional fluid attenuation reversal recovery sequence(3DFLAIR)and its clinical application value in the large vestibular aqueduct(LVA).Methods A retrospective analysis was conducted on 328 cases(649 ears)of LVA with HRCT and MRI[3-dimensional sampling perfection with application-optimized contrasts by different flip angle evolution(3D-SPACE)and 3D-FLAIR].Based on the range of the high signal in the ED and ES of LVA on 3D-FLAIR,they were classified into 3 types:Type Ⅰ,showing no high signal on 3D-FLAIR;Type Ⅱ,Partial high signal on 3D-FLAIR;and Type Ⅲ,appearing complete high signal on 3D-FLAIR.Then,we calculated the incidence of high signal in the inner ear and ED and ES on 3D-FLAIR,as well as the complete displaying rate of ED and ES in the LVA ears on 3D-SPACE and 3D-FLAIR,analyzed their differences using chi square test,and discussed the reasons for false negatives in LVA ears diagnosed by 3D-SPACE.Results The incidence of high signal in the inner ear,ED and ES of 328 LVA patients with 649 ears was 49.0% and 91.7%,respectively.The range and intensity of the high signal intensity on 3D-FLAIR in the ED and ES of the affected ears were variable.Among them,54 ears(8.3%),570 ears(87.8%),and 25 ears(3.9%)belonged to type Ⅰ,Ⅱ,and Ⅲ,respectively.The complete displaying rates of ED and ES in the affected ear by 3D-SPACE and 3D-FLAIR were 93.7% and 4.2%,respectively,and the difference between them was statistically significant(χ^(2)=1040.7,P<0.05).The accuracy rates of 3D-SPACE and 3D-SPACE+3D-FLAIR were 95.7%(621/649)and 100%(649/649),respectively,and there was statistically significant difference between them(χ^(2)=28.6,P<0.05).The analysis of 19 false negative LVA cases(28 ears)on 3D-SPACE was as follows:the vestibular aqueduct(VA)in two LVA ears presented markedly dilation on HRCT,and the signals in the affected ED and ES were deadly low similar to adjacent bone on 3D-SPACE,which made them difficult be displayed,while they could be clearly displayed as high signal on 3D-FLAIR.In the other 26 LVA ears,the degree of the dilation of the affected VAs was relatively mild or normal-like on HRCT.The degree of dilation of the inner and outer ossous parts of the ED and ES was also relatively mild,and the signal in the distal portions was complex,which made the ED and ES be difficult to display on 3D-SPACE,but shown high signal could be easily diagnosed on 3D-FLAIR.Conclusion Abnormal signals in the inner ear,ED and ES of LVA patients might be one of the MRI appearing features.3D-FLAIR is not suitable for standalone application in LVA diagnosis,and its combination with 3D-SPACE can help improve the diagnostic accuracy of some LVA.