My first MRI was pretty close to what you described, and they recommended a spinal tap. It hurt like HELL. Mine was positive for bands, and then they did an MRI of the spine. That, combined with my past weird symptoms that never seemed to make sense, along with negative HIV/PML/Lyme tests, got me a dx of MS.
Diagnosed with RRMS March 2013.
Rebif May 2013 - September 2014.
Gilenya since November 2014.