大前庭导水管综合征内淋巴囊和前庭导水管MRI信号特征及其临床意义

目的 探讨大前庭导水管综合征患者内淋巴囊和前庭导水管MRI信号特征及其与听力损失的关系.方法 搜集大前庭导水管综合征31例共62只内耳的MRI和听力资料.MRI表现分4型:I型的内淋巴囊及前庭导水管裂隙范围内均为低信号区,无高信号区；Ⅱ～Ⅳ型除低信号区外,还可见高信号区；Ⅱ型的高信号区局限于前庭导水管裂隙内；Ⅲ型的高信号区自前庭导水管裂隙向后超出岩骨后缘,但其下界在后半规管下脚平面以上,在平面以下者为Ⅳ型.为避免肉眼观察误差,测量内淋巴囊高信号区、低信号区和前庭的信号强度,并与同层脑脊液信号强度比较.采用配对t检验分析内淋巴囊高信号区与低信号区、前庭之间信号强度的差异,纠正卡方检验,用Spearman分析判断内淋巴囊MRI分型与听力损失程度的相关性.结果 31例共62耳中Ⅰ型10耳(听力下降为中度1耳,重度4耳,极重度5耳)；Ⅱ型17耳(听力下降为中度1耳,重度5耳,极重度11耳)；Ⅲ型23耳(听力下降为中度3耳,重度5耳,极重度15耳)；Ⅳ型12耳(听力下降为轻度1耳,中度1耳,重度3耳,极重度7耳).高信号区与同层脑脊液信号强度的比值为0.95 ±0.12,低信号区为0.49±0.10,前庭为0.99±0.08,高、低信号区分界清楚,信号比值为2.02±0.06.高、低信号区间信号强度差异有统计学意义(t=- 24.966,P＜0.05),高信号区与前庭的信号差异无统计学意义(t=-24.966,P＞0.05).不同MRI分型对应的听力损失差异无统计学意义(似然比值为5.02,P＞0.05),高、低信号区强度比值与听力损失无相关性(r=0.135,P=0.297).结论 大前庭导水管综合征不只是内淋巴囊扩大,也可以伴有外淋巴液疝入前庭导水管骨性裂隙中；内淋巴囊MRI信号特征与听力损失程度之间未见相关.

MR imaging features and clinical value of vestibular aqueduct and endolymphatic sac in patients with large vestibular aqueduct syndrome

Objective To investigate MR imaging features of endolymphatic sac and vestibular aqueduct in patients with large vestibular aqueduct syndrome (LVAS) and its correlation with hearing loss.Methods MR imaging findings of LVAS were analyzed in 31 cases (62 ears) retrospectively.MR imaging features were grouped into 4 types.In the first type,the signals of endolymphatic and vesitibular aqueduct were hypointense without any hyperintense area.In the second type,the signals of endolymphatic sac and vestibular were hyperintense which were confined within vestibular fissure.In the third type,the area from vestibular aqueduct backward out of the edge of the petrous bone was hyperintense,but its lower boundary was above posterior semicircular.In the fourth type the area which was hyperintense was below the posterior semicircular.To avoid errors in visual inspection,the hyperintense and hypointense area of endolymphatic and the signal intensity of vestibular aqueduct and cerebrospinal fluid (CSF) were measured.The differences of signal intensity among the vestibular endolymphatic sac between the high-signal areas and lowsignal areas were compared with paired t-test.The correlation of the endolymphatic sac MRI classification and degree of hearing loss was analyzed by corrected Chi-square test and Spearman correlation analysis.Result Ten ears belonged to type Ⅰ (moderate hearing loss in 1 ear,severe in 4 ears,profound in 5 ears),17 ears belonged to type Ⅱ ( moderate hearing loss in 1 ear; severe in 5 ears,profound in 11 ears),23 ears to type Ⅲ (moderate hearing loss in 3 ear,severe in 5 ears,profound in 15 ears) and 12 ears belonged to Ⅳ(mild hearing loss in 1 ear,moderate in 1 ear,severe 3 ear,profound in 7 ears).The boundary between hyperintense and hypointense area was clear,and the signal intensity ratios was 2.02 ± 0.06.The signal ratios of hyperintense and hypointense area to vestibular and CSF were 0.95 ±0.12,0.49 ±0.10,0.99 ± 0.08 respecitively.So there was statistical significant difference between hyperintense and hypointense area ( t =- 24.966,P ＜ 0.05 ),but there was no statistical significant difference between hyperintense area and vesitbular( t =-24.966,P ＞ 0.05).There was no difference of hearing loss between different MRI types ( likelihood ratio =5.02,P ＞ 0.05 ).Conclusions Not only endolymphatic sac enlarged but also perilymph herniated into skeletal fissures of vestibular aqueduct in patients with LVAS.The signal intensity of the endolymphatic sac did not show significant correlation with degree of hearing loss.