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. Author manuscript; available in PMC: 2014 Apr 1.
Published in final edited form as: Nat Rev Neurosci. 2013 Mar 13;14(4):265–277. doi: 10.1038/nrn3468

Figure 3. Routes of water flow into and out of the CNS in brain oedema.

Figure 3

In cytotoxic oedema, water enters the CNS through aquaporin 4 (AQP4) that is located in perivascular astrocyte foot processes. In vasogenic oedema, CNS water entry is AQP4-independent and occurs through intercellular spaces. In hydrocephalic oedema, water enters the brain through AQP4 in ependymal cells and subependymal astrocytes. Oedema fluid is eliminated through three AQP4-dependent routes: from astrocyte foot processes into the bloodstream, across subpial astrocyte processes and pial cells into subarachnoid cerebrospinal fluid (CSF), and across subependymal astrocyte processes and ependyma into ventricle.