Mazerolle Erin L, Warwaruk-Rogers Robyn, Romo Paul, Sankar Tejas, Scott Sarah, Rockel Conrad P, Pichardo Samuel, Martino Davide, Kiss Zelma H T, Pike G Bruce
Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
Neuroimage Rep. 2021 Apr 30;1(1):100010. doi: 10.1016/j.ynirp.2021.100010. eCollection 2021 Mar.
We describe diffusion tensor imaging metrics of brain microstructure changes following magnetic resonance guided focused ultrasound (MRgFUS) ablation of the ventral intermediate nucleus of the thalamus for the treatment of tremor in order to explore the mechanisms of tremor reduction post-MRgFUS. Tractography was performed on pre-treatment images to identify the portion of the dentato-rubro-thalamo-cortical tract (DRTT) intersecting the MRgFUS thalamotomy lesions in 17 essential tremor patients. The resulting tract was divided into regions of interest (ROI), which were then analyzed on pre-, one day post-, and three months post-treatment scans. Fractional anisotropy (FA), and mean, axial, and radial diffusivity (MD, AD, and RD) were computed in each ROI at each time point. At both one day and three months post-treatment, we observed decreased FA and increased MD and RD in the section of the treated tract between the lesion and cortex. At three months post-treatment, we additionally observed increased AD in the section between the lesion and cortex, and decreased FA in the section between the dentate nucleus and the decussation of the superior cerebellar peduncles. Diffusion changes at one day post-treatment may reflect local, acute effects such as inflammation and edema, as opposed to chronic degenerative processes such as axonal degeneration and myelin loss that would be expected at later time points. No significant correlations were detected between diffusion measures and clinical effects, suggesting that microstructural changes in the treated portion of the DRTT alone do not fully explain tremor reduction and motivating additional research using higher spatial resolution diffusion imaging and multimodal approaches such as integrating diffusion and functional magnetic resonance imaging data. Our individualized approach, in which patient-specific lesions are incorporated into the tractography analysis, provided novel insight into both immediate and longer term MRgFUS-related microstructural brain changes.
我们描述了磁共振引导聚焦超声（MRgFUS）丘脑腹中间核消融治疗震颤后脑微结构变化的扩散张量成像指标，以探讨MRgFUS术后震颤减轻的机制。对17例特发性震颤患者的治疗前图像进行纤维束成像，以确定齿状核-红核-丘脑-皮质束（DRTT）与MRgFUS丘脑切开术病变相交的部分。将所得纤维束划分为感兴趣区域（ROI），然后在治疗前、治疗后1天和3个月的扫描中对其进行分析。在每个时间点的每个ROI中计算分数各向异性（FA）以及平均、轴向和径向扩散率（MD、AD和RD）。在治疗后1天和3个月时，我们观察到病变与皮质之间的治疗纤维束段FA降低，MD和RD升高。在治疗后3个月时，我们还观察到病变与皮质之间的纤维束段AD增加，齿状核与小脑上脚交叉之间的纤维束段FA降低。治疗后1天的扩散变化可能反映局部急性效应，如炎症和水肿，而非后期预期的慢性退行性过程，如轴突退变和髓鞘丢失。在扩散测量与临床效果之间未检测到显著相关性，这表明单独DRTT治疗部分的微结构变化不能完全解释震颤减轻，这促使我们使用更高空间分辨率的扩散成像和多模态方法（如整合扩散和功能磁共振成像数据）进行更多研究。我们的个体化方法将患者特异性病变纳入纤维束成像分析，为MRgFUS相关的脑微结构即时和长期变化提供了新的见解。
