My son had been taking Tysabri for 3 1/2 years. During that time he’s had at least 3 blackouts where he has had very bizarre behavior but does not remember any of it. The neurologist said it wasn’t caused by the Tysabri, I disagree. This past June he went off of Tysabri and in August started taking the pill Tecfidera. Last week he had another blackout! Again the neurology office said it wasn’t the med that he should call his PCP. I really think it’s these medications causing the blackouts.