ICP can be mesured from the lateral ventricle (Oshio K et al., FASEB J, 2005 ). But I have not found any data of pressure inside the brain tissue. Probably they are quite close to each other in healthy brian, otherwise the brain tissue would expand or being squeezed.
Anyone has a scientific answer to this question? It is better if you can precise the difference!
Cheers!
The icp is the effect of the volume of blood, liquor and water inside the scull. The pressure is transmitted through all material (tissue /liquid) and therefore the same.
When caring for patients in a clinical settings it is possible to messure icp in tissue or in the ventricles. They are considered equal.
I think the Monroe Kelly doctrine would support what Jonas has said. Liquid is more compressible, but pressure would be transmitted across all tissues. When all liquid extruded (not clinically realistic) the PV curve becomes exponential again (less compliant) as just tissue is compressed. The clinically realistic scenario is tonsillar herniation
Both Drs Blixt and Sheeran have given good explanations. I am an engineer and a neurologic clinician so will add my two bits. In Vivo Brain tissue has roughly the consistency of an overcooked flan and is floating in CSF and has cavities within it, filled with CSF (the ventricles, obviously). Normally, all the cavities communicate and so pressure differences cannot occur. So in a constant hydrostatic environment the brain tissue will be the same within the brain tissue as all around it. Brain tissue is passive and moves, deforms, and follows the laws of fluid mechanics of the liquid volume that surrounds it, like a jellyfish in a bathtub. Things change when you pull the plug and the jellyfish hits the drain with a positive pressure gradient that rips it apart....if the pressure DIFFERENCE between the tub and the drain below is greater than the intrinsic viscoelastic resistance of the brain tissue, the brain will be ripped apart and the fluid pressure between the tub and the drain will even out. But even in THAT situation (which is what coning from hydrocephalus or significant hemorrhage is, right?) the pressure within the brain tissue will decrease almost linearly between the higher pressure vault and the lower pressure vault.....I say ALMOST because of intrinsic internal resistance to the fluid flow through the interstices of the brain parenchyma like water through a sponge...but that has to be next to nothing, is very short-lived, and is PASSIVE, in any event. Hope that helps.
Hi Jonas Blix, I am curious of how can you measure the pressure from tissue without . Could you give me a hint?
And thanks to all, the Monroe Kelly doctrine has very interesting implications (http://www.ncbi.nlm.nih.gov/pubmed/11425944) and very detailed explanations from Gergory.
I want to have to estimate/control the size of tracer injection by a rough calculation, based on the difference between external air pressue and that of deep brain nucleus. So your answers here are obviously helpful. But I also need to consider the shape of glass pipette used for injection and the viscosity of tracer in the tissue (which it is difficult to assess by the way).
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