Increased Cellular Permeability: The name has changed from Sympathetic Neural Hyperalgesia Syndrome to Increased Cellular Permeability Syndrome. This is due to several factors. Not every patient had Hyperalgesia and/or edema.
The reason to eliminate “sympathetic neural” from the name is because the problem may be with a defect on the tissue and not the sympathetic nervous system. It may change again as more is discovered about this syndrome.
What Causes This Syndrome? This syndrome is caused by a defect in capillary permeability, thus allowing intravascular fluid to leak into the extravascular space. This fluid leakage is more pronounced in the sitting or standing position because there is an increase in hydrostatic pressure that occurs in the orthostatic position. (Note: Hydrostatic pressure is what is exerted by a liquid when it is at rest.) There seems to be a strong hereditary component to this disorder in many cases. This disorder could be leakage from capillaries or from all tissues. Hopefully with more research, we can definitively pinpoint exact causation.