Wang Xiaofei, Neely Andrew J, McIlwaine Gawn G, Tahtali Murat, Lillicrap Thomas P, Lueck Christian J
School of Engineering and Information Technology (XW, AJN, MT, TPL), University of New South Wales, Canberra, Australia; Department of Ophthalmology, Queen's University Belfast (GGM), Belfast, United Kingdom; Belfast Health and Social Care Trust (GGM), Belfast, United Kingdom; Department of Neurology, The Canberra Hospital (TPL, CJL), Canberra, Australia; and Medical School, Australian National University (TPL, CJL), Canberra, Australia.
J Neuroophthalmol. 2014 Dec;34(4):324-30. doi: 10.1097/WNO.0000000000000145.
The precise mechanism of bitemporal hemianopia is still not clear. Our study investigated the mechanism of bitemporal hemianopia by studying the biomechanics of chiasmal compression caused by a pituitary tumor growing below the optic chiasm.
Chiasmal compression and nerve fiber interaction in the chiasm were simulated numerically using finite element modeling software. Detailed mechanical strain distributions in the chiasm were obtained to help understand the mechanical behavior of the optic chiasm. Nerve fiber models were built to determine the relative difference in strain experienced by crossed and uncrossed nerve fibers.
The central aspect of the chiasm always experienced higher strains than the peripheral aspect when the chiasm was loaded centrally from beneath. Strains in the nasal (crossed) nerve fibers were dramatically higher than in temporal (uncrossed) nerve fibers.
The simulation results of the macroscopic chiasmal model are in agreement with the limited experimental results available, suggesting that the finite element method is an appropriate tool for analyzing chiasmal compression. Although the microscopic nerve fiber model was unvalidated because of lack of experimental data, it provided useful insights into a possible mechanism of bitemporal hemianopia. Specifically, it showed that the strain difference between crossed and uncrossed nerve fibers may account for the selective nerve damage, which gives rise to bitemporal hemianopia.
双颞侧偏盲的确切机制仍不清楚。我们的研究通过研究垂体瘤在视交叉下方生长导致视交叉受压的生物力学来探究双颞侧偏盲的机制。
使用有限元建模软件对视交叉受压及视交叉内神经纤维相互作用进行数值模拟。获得视交叉内详细的机械应变分布,以帮助了解视交叉的力学行为。构建神经纤维模型以确定交叉和未交叉神经纤维所经历应变的相对差异。
当视交叉从下方中央加载时,视交叉的中央部分总是比周边部分承受更高的应变。鼻侧(交叉)神经纤维的应变明显高于颞侧(未交叉)神经纤维。
宏观视交叉模型的模拟结果与现有的有限实验结果一致,表明有限元方法是分析视交叉受压的合适工具。尽管由于缺乏实验数据,微观神经纤维模型未得到验证,但它为双颞侧偏盲的可能机制提供了有用的见解。具体而言,它表明交叉和未交叉神经纤维之间的应变差异可能是导致选择性神经损伤的原因,进而引起双颞侧偏盲。