The acute phase of Wallerian degeneration: Longitudinal diffusion tensor imaging of the fornix following temporal lobe surgery
The acute phase of Wallerian degeneration: Longitudinal diffusion tensor imaging of the fornix following temporal lobe surgery
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DOI：
10.1016/j.neuroimage.2013.01.069
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发表时间：
2013-07-01
期刊：
影响因子：
5.7
通讯作者：
Beaulieu, Christian
中科院分区：
文献类型：
--
作者：
Liu, Min;Gross, Donald W.;Beaulieu, Christian
许多动物研究表明，扩散张量成像（DTI）的适用性，以跟踪沃勒变性后发生的神经纤维损伤。可以区分早期轴突断裂和后期髓鞘降解的非侵入性生物标志物已分别归因于平行扩散率降低和垂直扩散率升高。虽然几项人体DTI研究已经显示了亚急性和慢性时间点的这种潜力，但第一周内发生的扩散变化尚不清楚。前颞叶切除术（即海马切除术）是医学难治性颞叶癫痫的标准手术治疗。由于时间已知，穹窿海马伞的同时横断是检查Wallerian变性过程的独特机会。6例颞叶癫痫患者在术前、术后1周内3 ~ 4次、术后1 ~ 4个月进行脑DTI检查。在手术后的头两天内，同侧穹窿的平行和垂直扩散率均显著降低，降幅相似。接近第一周结束时，垂直（而不是平行）扩散率假性恢复到其术前值，但几个月后急剧增加。分数各向异性，作为平行和垂直扩散率的联合作用的结果，保持相对稳定的第一周内，只有在慢性阶段急剧减少。DTI显示，在横断的几天内，急性水扩散变化不仅限于平行扩散。虽然穹窿中的慢性扩散变化与髓鞘降解相容，但急性变化可能反映轴膜的珠状和肿胀、轴突神经丝的颗粒崩解、缺血诱导的细胞毒性水肿和/或轴突外空间的变化，包括炎性变化和神经胶质增生。(C)2013 Elsevier Inc. All rights reserved.
Numerous animal studies have shown the applicability of diffusion tensor imaging (DTI) to track Wallerian degeneration that occurs after injury to the neural fiber. Non-invasive biomarkers that may differentiate the early axonal breakdown and later myelin degradation have been attributed to either reduced parallel and elevated perpendicular diffusivity, respectively. While several human DTI studies have shown this potential at subacute and chronic time points, the diffusion changes that occur within the first week are unknown. Anterior temporal lobectomy (i.e. resection of hippocampus) is the standard surgical treatment of medically refractory temporal lobe epilepsy. The concomitant transection of the fimbria-fornix serves as a unique opportunity to examine the process of Wallerian degeneration since the timing is known. Six temporal lobe epilepsy patients underwent brain DTI before the surgery, three to four times within the first week post-operatively, and at one to four months following surgery. Both parallel and perpendicular diffusivities decreased markedly by a similar amount in the ipsilateral fornix within the first two days post-surgery. Approaching the end of the first week, perpendicular (but not parallel) diffusivity pseudo-recovered towards its pre-surgical value, but then increased dramatically months later. Fractional anisotropy, as a result of the combined action of the parallel and perpendicular diffusivities, stayed relatively stable within the first week and only reduced drastically at the chronic stage. DTI demonstrated acute water diffusion changes within days of transection that are not just limited to parallel diffusivity. While the chronic diffusion changes in the fornix are compatible with myelin degradation, the acute changes may reflect beading and swelling of axolemma, granular disintegration of the axonal neurofilaments, ischemia induced cytotoxic edema, and/or changes in the extra-axonal space including inflammatory changes and gliosis. (C) 2013 Elsevier Inc. All rights reserved.