Pulsating tinnitus only when Laying down

I have chronic jaw under the ear area and neck pain for 3 years now, without knowing the cause of the pain yet. I have had MRI and CT of jaw and neck. My MRI report of the jaw shows, Incidental finding of right side sigmoid bulb venous diverticulum. I asked the oral surgeon who ordered the MRI scan of jaw. He said he don't know what this means and asked me to go to the GP. I have pulsating tinnitus only when I lay down at night on my sides on the pillow. Hearing it on both sides. I mean if I lay down on my sides, I hear the pulsating tinnitus on that side. If I lay on my back, I don't hear it. Is this something serious? Is the incident finding related to this pulse tinnitus? I hear like heart pulse in the ear like pulsing heartbeat. Is this something serious? Do I need any surgery? Will this go away on its own? Do I need to see an ENT or neurologist for this issue? How is this treated? Please help.