Struggling with Neurofibromatosis and Insurance Coverage

so I was diagnosed with NF type 1 and 2011 at Tufts in Boston. I've had two MRIs and the doctor wanted to have me have two a year. well the insurance companies thought that was too much and have refused to cover any. I could not afford to pay for them out of pocket and have since let any treatment or follow-ups lapse. I've noticed my vision change as well as multiple headaches in migraines a week. I know I have multiple tumors in my brain and on the optic nerve as well as hundreds if not thousands of neurofibromas all over my body.