MS is a complex diagnosis. There is no one test to determine if someone has MS. The diagnosis should only be made after a detailed interview, thorough neurological examination, extensive blood work, and magnetic resonance imaging (MRI). Additional tests, such as a lumbar puncture (also known as a spinal tap) or visual evoked potentials (VEPs) are sometimes required. A number of other illnesses can mimic MS and should be excluded before a diagnosis is made.