Background

Posterior fossa decompression (PFD) surgery is a treatment for Chiari malformation type I (CMI). The goals of surgery are to reduce cerebellar tonsillar crowding and restore posterior cerebral spinal fluid flow, but regional tissue biomechanics may also change. MRI-based displacement encoding with stimulated echoes (DENSE) can be used to assess neural tissue displacement.

Purpose

To assess neural tissue displacement by using DENSE MRI in participants with CMI before and after PFD surgery and examine associations between tissue displacement and symptoms.

Materials and Methods

In a prospective, HIPAA-compliant study of patients with CMI, midsagittal DENSE MRI was performed before and after PFD surgery between January 2017 and June 2020. Peak tissue displacement over the cardiac cycle was quantified in the cerebellum and brainstem, averaged over each structure, and compared before and after surgery. Paired t tests and nonparametric Wilcoxon signed-rank tests were used to identify surgical changes in displacement, and Spearman correlations were determined between tissue displacement and presurgery symptoms.

Results

Twenty-three participants were included (mean age ± standard deviation, 37 years ± 10; 19 women). Spatially averaged (mean) peak tissue displacement demonstrated reductions of 46% (79/171 µm) within the cerebellum and 22% (46/210 µm) within the brainstem after surgery (P < .001). Maximum peak displacement, calculated within a circular 30-mm² area, decreased by 64% (274/427 µm) in the cerebellum and 33% (100/300 µm) in the brainstem (P < .001). No significant associations were identified between tissue displacement and CMI symptoms (r < .74 and P > .012 for all; Bonferroni-corrected P = .0002).

Conclusion

Neural tissue displacement was reduced after posterior fossa decompression surgery, indicating that surgical intervention changes brain tissue biomechanics. For participants with Chiari malformation type I, no relationship was identified between presurgery tissue displacement and presurgical symptoms.

© RSNA, 2021

Online supplemental material is available for this article.

中文翻译：

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后颅窝减压手术后使用 DENSE MRI 测量 Chiari 畸形的小脑和脑干位移

背景

后颅窝减压 (PFD) 手术是治疗 Chiari 畸形 I 型 (CMI) 的一种方法。手术的目标是减少小脑扁桃体拥挤和恢复脑脊液后部流动，但区域组织生物力学也可能发生变化。基于 MRI 的受激回波位移编码 (DENSE) 可用于评估神经组织位移。

目的

在 PFD 手术前后使用 DENSE MRI 评估 CMI 参与者的神经组织移位，并检查组织移位与症状之间的关联。

材料和方法

在一项针对 CMI 患者的符合 HIPAA 的前瞻性研究中，在 2017 年 1 月至 2020 年 6 月期间，在 PFD 手术前后进行了中矢状位 DENSE MRI。在小脑和脑干中量化了心动周期中的峰值组织位移，对每个结构进行平均，并比较手术前后。配对t检验和非参数 Wilcoxon 符号秩检验用于识别移位的手术变化，并确定组织移位和术前症状之间的 Spearman 相关性。

结果

包括 23 名参与者（平均年龄 ± 标准差，37 岁 ± 10；19 名女性）。空间平均（平均）峰值组织位移表明，手术后小脑内减少了 46% (79/171 µm)，脑干内减少了 22% (46/210 µm) ( P < .001)。在圆形 30-mm ²区域内计算的最大峰值位移在小脑中减少了 64% (274/427 µm)，在脑干中减少了 33% (100/300 µm) ( P < .001)。没有发现组织移位和 CMI 症状之间存在显着关联（所有的r < .74 和P > .012；Bonferroni 校正的P = .0002）。

结论

后颅窝减压手术后神经组织移位减少，表明手术干预改变了脑组织生物力学。对于 Chiari I 型畸形的参与者，未发现术前组织移位与术前症状之间存在关系。

© 北美放射学会，2021

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