Syrinx Fluid Transport: Modeling Pressure-Wave-Induced Flux Across the Spinal Pial Membrane
Syrinx Fluid Transport: Modeling Pressure-Wave-Induced Flux Across the Spinal Pial Membrane
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DOI：
10.1115/1.4005849
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发表时间：
2012-03-01
影响因子：
1.7
通讯作者：
Elliott, N. S. J.
中科院分区：
文献类型：
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作者：
Elliott, N. S. J.
脊髓空洞是脊髓内充满液体的空洞，是脊髓空洞症的特征，脊髓空洞症是一种涉及神经损伤的疾病。人们对它们的形成和扩张知之甚少，这阻碍了成功的治疗。脊髓腔通过脊髓间质和血管周围间隙网络（PVSs）与包裹脊髓的脊髓蛛网膜下腔（SSS）水力连接，PVSs围绕着穿过脊髓表面的脊髓膜的血管。由于椎管支持压力波的传播，因此有假设认为，压力波引起的液体交换可能在脊髓膜上发挥作用。为了验证这一猜想，在经典弹性管理论和达西定律的基础上建立了一对一维（1-d）的血管周围或间隙流动分析模型。结果表明，经皮通量通过减轻枕膜内的环向应力而起到抑制压力波的作用。粘滞力和惯性力竞争的时间尺度比被明确地确定，这预示着PVS扩张、SSS流动障碍和更硬、更厚的头膜——所有这些都与脊髓空洞有关——将增加透射通量，延缓波的传播。研究还发现，压力波的传播是由渗透性较差的枕膜和渗透性较强的脊髓共同作用的。这是第一个既包括沿脊髓轴的压力波传播，又包括液体进出脊髓的通道的椎管模型，这为研究全孔弹性问题提供了分析基础。(DOI: 10.1115/1.4005849)
Syrinxes are fluid-filled cavities of the spinal cord that characterize syringomyelia, a disease involving neurological damage. Their formation and expansion is poorly understood, which has hindered successful treatment. Syrinx cavities are hydraulically connected with the spinal subarachnoid space (SSS) enveloping the spinal cord via the cord interstitium and the network of perivascular spaces (PVSs), which surround blood vessels penetrating the pial membrane that is adherent to the cord surface. Since the spinal canal supports pressure wave propagation, it has been hypothesized that wave-induced fluid exchange across the pial membrane may play a role in syrinx filling. To investigate this conjecture a pair of one-dimensional (1-d) analytical models were developed from classical elastic tube theory coupled with Darcy's law for either perivascular or interstitial flow. The results show that transpial flux serves as a mechanism for damping pressure waves by alleviating hoop stress in the pial membrane. The timescale ratio over which viscous and inertial forces compete was explicitly determined, which predicts that dilated PVS, SSS flow obstructions, and a stiffer and thicker pial membrane-all associated with syringomyelia-will increase transpial flux and retard wave travel. It was also revealed that the propagation of a pressure wave is aided by a less-permeable pial membrane and, in contrast, by a more-permeable spinal cord. This is the first modeling of the spinal canal to include both pressure-wave propagation along the spinal axis and a pathway for fluid to enter and leave the cord, which provides an analytical foundation from which to approach the full poroelastic problem. [DOI: 10.1115/1.4005849]