My Husband Has A Spinal Chord Stimulator For Him Ms,

my husband has a spinal chord stimulator for him ms, making a mri impossible. his neurologist says a cat scan won't show clearly and new lesions on his brain...he's had two exasperations in 3 months....one on christmas day which had him in a rehab center for 7 weeks and one yesterday on easter. what other test can be done on his brain?