You CAN have a negative spinal tap and still have MS.

You do not need contrast on a MRI to diagnosis MS, Contrast shows new lesions that are between 30-45 days new....but all lesions will show on a non-contrast MRI, the doctor just will not know if the are new.

I had my initial MRI with contrast....but I refuse to anymore, I don't want that toxin in my body, I have enough to deal with.

Hope that helps. Also, your doctor is looking at your clinical symptoms and your neuro exam in combination with all these test. MS is a Clinical diagnosis.