@kaybast
I've had PT for several years now. I too had a brain scan and and all that was noted were a few very small brain bleeds which I was told at age 75 was not unusual.
I believe my cause is rooted in the arthritis now in my neck resulting from an auto accident at age 16 for which the car I was riding in rear-ended the car in front of them. No seat belts in the vehicle back then and I was thrown from the passenger seat into the windshield. Hitting and cracking the windshield with my forehead resulted in 3 tilted discs causing traumatic arthritis in neck in my old age.
I hear my heartbeat or pulse all the time in my left ear. I just tried putting my finger in my ear like you mentioned and it magnifies the sound of the heartbeat or pulse. It varies in volume but my tinnitus sounds like water running in the house pipes. Initially I would get up at night to find the source of the running water thinking a toilet was running. My husband never heard it. I eventually figured out the sound was heard only on my left side and searching the internet I figured our the name of this affliction.