CT Scans #13 and the Blood/Brain Barrier

CT Scans:


     My last scans were in January and I was hoping to avoid my next set until at least June. However, while traveling in Israel, I noticed more upper right quadrant pain so I recently had CT scans and blood tumor markers drawn.  I am happy and relieved to report that everything continues to indicate that my disease is stable, below my neck.  I still don't know why I have periodic pain in my abdomen, but I'm glad that when it comes...it eventually goes. 

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The Blood/Brain Barrier (BBB):
     ...has been something I've referred to in previous blogs.  I didn't know very much about the BBB, or how it works, so I thought I'd read up and blog about it.  As fascinating as it is, it's pretty complicated.  Some aspects of the BBB are still not fully understood by researchers and some aspects could not be fully understood by yours truly.  Since I only understand the basics, that's all I can share.  Here goes...

     The BBB's purpose is to protect the central nervous system (the brain and spinal cord), from potentially harmful chemicals and infections.  It is semi-permeable, allowing molecules needed to maintain stability, (necessary hormones and key nutrients), into the brain while keeping toxins out.  The brain is the only organ that has a protective mechanism such as this. 

     The BBB runs within the blood vessels of the brain and is not present in the vessels in other parts of our body.  The smallest blood vessels in our bodies are called capillaries.  Capillaries are lined with endothelial cells, which are loosely packed together.  This "loose-ness" allows most molecules, big and small, to flow around the endothelial cells and then pass from our blood capillaries into our organs.  

     The endothelial cells lining the capillaries of our brain are different. Unlike the endothelial cells found lining the capillaries in other parts of our body, the endothelial cells of the brain's capillaries are very tightly packed together, leaving virtually no space between the cells.  So tightly wedged together, these cells create an almost impermeable barrier between the brain and the bloodstream...especially for large molecule compounds.  Compounds that are very small molecules and/or fat-soluble easily pass into the brain.

(There are two other types of cells, astrocytes and pericytes, which also appear to play a role in the BBB.  In the resources I read, their roles don't seem to be as definitively understood yet.) 


     There are a few reasons the brain is not 100% protected, 100% of the time:

1. Not all parts of the brain are protected by the BBB.
2. Certain conditions can breakdown the BBB or alter its permeability: 
• Hypertension
• Exposure to microwave and radiation
• Some infections
• CNS injury or trauma resulting in inflammation, ischemia (an inadequate blood supply) or changes in intracranial pressure
• Hyperosmolarity, or a high concentration of a substance in the blood

     For me, the BBB has kept my targeted oral chemotherapy, Xalkori, from getting to my brain.  Therefore, I knew my brain was vulnerable to metastatic disease. Now that I have had CyberKnife, (radiation), it's my hope that my BBB's permeability has been altered enough to allow Xalkori into my brain and it will be better protected. The downside is that my BBB has been breached - and of course I now worry that other crap, that I don't want in my brain, can now enter.  

Ohhhhhh...the life of a stage 4 cancer patient.