Over the last 7 years, I started having a slowly worsening head/brain problem. The symptoms happen when I am sleeping on my back. It feels like the blood flow is partially blocked through the left rear of my head. I awake to my head pounding on left side, and my heart pounding. If I roll over to my right side or onto my stomach (with head to the right), then the symptoms slowly subside over the next 30 minutes. Last year I had MRIs done and the only abnormality mentioned was a giant arachnoid granulation.