RESUMO
Injuries such as traumatic brain injury and stroke can result in increased blood-brain barrier (BBB) permeability. This increase may lead to water accumulation in the brain tissue resulting in vasogenic oedema. Although the initial injury may be localized, the resulting oedema causes mechanical damage and compression of the vasculature beyond the original injury site. We employ a biphasic mixture model to investigate the consequences of BBB permeability changes within a region of brain tissue and the onset of vasogenic oedema. We find that such localized changes can indeed result in brain tissue swelling and suggest that the type of damage that results (stress damage or strain damage) depends on the ability of the brain to clear oedema fluid.
Assuntos
Barreira Hematoencefálica/lesões , Barreira Hematoencefálica/fisiopatologia , Edema Encefálico/fisiopatologia , Modelos Neurológicos , Fenômenos Biomecânicos , Edema Encefálico/etiologia , Permeabilidade Capilar/fisiologia , Simulação por Computador , Humanos , Hidrodinâmica , Conceitos Matemáticos , Dinâmica não LinearRESUMO
Brain tissue swelling, or oedema, is a dangerous consequence of traumatic brain injury and stroke. In particular, a locally swollen region can cause the injury to propagate further through the brain: swelling causes mechanical compression of the vasculature in the surrounding tissue and so can cut off that tissue's oxygen supply. We use a triphasic mathematical model to investigate this propagation, and couple tissue mechanics with oxygen delivery. Starting from a fully coupled, finite elasticity, model, we show that simplifications can be made that allow us to express the volume of the propagating region of damage analytically in terms of key parameters. Our results show that performing a craniectomy, to alleviate pressure in the brain and allow the tissue to swell outwards, reduces the propagation of damage; this finding agrees with experimental observations.
Assuntos
Edema Encefálico/fisiopatologia , Lesões Encefálicas/fisiopatologia , Encéfalo/fisiopatologia , Pressão Intracraniana , Modelos Neurológicos , Oxigênio/metabolismo , Animais , Encéfalo/cirurgia , Edema Encefálico/etiologia , Edema Encefálico/cirurgia , Lesões Encefálicas/complicações , Simulação por Computador , Descompressão Cirúrgica , Humanos , Ratos , Resultado do TratamentoRESUMO
Brain tissue swelling is a dangerous consequence of traumatic injury and is associated with raised intracranial pressure and restricted blood flow. We consider the mechanical effects that drive swelling of brain tissue slices in an ionic solution bath, motivated by recent experimental results that showed that the volume change of tissue slices depends on the ionic concentration of the bathing solution. This result was attributed to the presence of large charged molecules that induce ion concentration gradients to ensure electroneutrality (the Donnan effect), leading to osmotic pressures and water accumulation. We use a mathematical triphasic model for soft tissue to characterize the underlying processes that could lead to the volume changes observed experimentally. We suggest that swelling is caused by an osmotic pressure increase driven by both non-permeating solutes released by necrotic cells, in addition to the Donnan effect. Both effects are necessary to explain the dependence of the tissue slice volume on the ionic bath concentration that was observed experimentally.
