Hi
Welcome to the MedHelp forum!
Pain behind the ear could be due to otitis media, mastoiditis, infection in the tooth and TMJ. You need to consult an ENT specialist to run various tests to rule these out. I am not sure what lesions you have in the brain. However if these lesions are pressing on the auditory nerve, then this too can cause pain. Even as I write this, I think it is highly improbable that the brain lesions are causing the pain. It can also be a pinched cervical spinal nerve and a MRI of the cervical spine will be needed. Do discuss this with your doctor and get yourself examined.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
To test for aneurysm, they should run an MRA/MRV. It is an MRI where they look specifically at the blood vessels in your head. But you may want to consider TMJ dysfunction.... does your left jaw ever click or pop? I have arthritis in my jaws and it can be very painful and sometimes the pain the refers into my ear area and also can give me migraines.