You need to go see a neurologist. Dawson's fingers is just another name for MS lesions. It is a particular pattern of lesions. It could be something else but I have only heard Dawson's fingers associated with MS. Seems to me you should not start a "big gun" therapy until you have seen a neurologist with the results of your MRI.
I am sorry your Crohn's is so out of control. Are they still using tysabri for Crohn's? Tysabri is a drug they use for MS. It is very very effective for putting the breaks on MS, however it is now considered a drug that you should only take for 18 to 24 months due to PML. PML is a deadly brain infection that is considered a rare side effect of Tysabri. Your risk goes up the longer you are on it. Meanwhile, it is a very effective treatment.
I hope a neuro can rule out MS for you. I am terribly worried however. Dawson's fingers doesn't appear to be common at all. It is considered a pretty classic MS indicator. Please ask any questions you may want. Best of luck to you!