MS or Frederick's Ataxia

I am feeling frustrated and scared. I have had MRIs of the spine and head; the brain showed white lesions, but the spinal MRI was clear. I also had an LP that was negative for MS. My neurologist is now questioning Frederick's Ataxia. My father had MS, and my brother has FA. I'm questioning whether one or both were misdiagnosed. The neurologist wants to repeat the spinal MRI and wants me to get genetic testing. (I am still waiting to get an appointment for either). Not sure which is the worst diagnosis, FA has slower progression but there is no treatment.