Tumani Hayrettin, Huss André, Bachhuber Franziska
Department of Neurology, University Hospital Ulm, Ulm, Germany; Specialty Hospital of Neurology, Dietenbronn, Schwendi, Germany.
Department of Neurology, University Hospital Ulm, Ulm, Germany.
Handb Clin Neurol. 2017;146:21-32. doi: 10.1016/B978-0-12-804279-3.00002-2.
The cerebrospinal fluid (CSF) space consists of the intracerebral ventricles, subarachnoid spaces of the spine and brain (e.g., cisterns and sulci), and the central spinal cord canal. The CSF protects the central nervous system (CNS) in different ways involving metabolic homeostasis, supply of nutrients, functioning as lymphatic system, and regulation of intracranial pressure. CSF is produced by the choroid plexus, brain interstitium, and meninges, and it circulates in a craniocaudal direction from ventricles to spinal subarachnoid space from where it is removed via craniocaudal lymphatic routes and the venous system. The CSF is renewed 3-5 times daily and its molecular constituents are mainly blood-derived (80%), while the remainder consists of brain-derived and intrathecally produced molecules (20%). The CSF space is separated from the vascular system by the blood-CSF barrier (BCB), whereas the blood-brain barrier (BBB), responsible for maintaining the homeostasis of the brain, is located between brain parenchyma and vascular system. Although both barriers have similar functions, they differ with regard to their morphologic and functional properties. Both barrier systems are permeable not only for small molecules, but also for macromolecules and circulating cells. The transport of molecules across the BBB and BCB is regulated by passive diffusion (e.g., albumin, immunoglobulins) and facilitated or active transport (e.g., glucose). The extracellular space volume, potassium buffering, CSF circulation, and interstitial fluid absorption are mainly regulated by aquaporin-4 channels, which are abundantly located at the blood-brain and brain-CSF interfaces. The composition of CSF shows a high dynamic range, and the levels of distinct proteins vary due to several influencing factors, such as site of production (brain or blood-derived), site of sampling (ventricular or lumbar), CSF flow rate (BCB function), diurnal fluctuations of CSF production rate, and finally, molecular size of blood-derived proteins (IgM vs. albumin) and circadian rhythm (glucose, prostaglandin D synthase). Alterations of lumbar CSF are mainly influenced by processes of the CNS located adjacent to the ventricular and spinal CSF space and less by pathologies in cortical areas remote from the ventricles.
脑脊液（CSF）空间由脑室内腔、脊柱和脑的蛛网膜下腔（如脑池和脑沟）以及脊髓中央管组成。脑脊液以不同方式保护中枢神经系统（CNS），包括代谢稳态、营养物质供应、充当淋巴系统以及调节颅内压。脑脊液由脉络丛、脑间质和脑膜产生，并从脑室向颅尾方向循环至脊髓蛛网膜下腔，然后通过颅尾淋巴途径和静脉系统排出。脑脊液每天更新3至5次，其分子成分主要来源于血液（80%），其余部分由脑源性和鞘内产生的分子组成（20%）。脑脊液空间通过血脑脊液屏障（BCB）与血管系统分隔，而负责维持脑内稳态的血脑屏障（BBB）位于脑实质和血管系统之间。尽管这两种屏障功能相似，但在形态和功能特性方面存在差异。这两种屏障系统不仅对小分子通透，对大分子和循环细胞也通透。分子通过血脑屏障和血脑脊液屏障的转运受被动扩散（如白蛋白、免疫球蛋白）以及易化或主动转运（如葡萄糖）调节。细胞外间隙容积、钾缓冲、脑脊液循环和间质液吸收主要由水通道蛋白4通道调节，这些通道大量位于血脑和脑脑脊液界面。脑脊液的成分显示出高动态范围，不同蛋白质的水平因多种影响因素而变化，如产生部位（脑源性或血源性）、采样部位（脑室或腰椎）、脑脊液流速（血脑脊液屏障功能）、脑脊液产生率的昼夜波动，最后还有血源性蛋白质的分子大小（IgM与白蛋白）和昼夜节律（葡萄糖、前列腺素D合成酶）。腰椎脑脊液的改变主要受位于脑室和脊髓脑脊液空间附近的中枢神经系统过程影响，而受远离脑室的皮质区域病变的影响较小。
