Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the cause of your symptoms are. However, I will try to provide you with some useful information.
Remicaide can neurologic side effects. The most worrisome would be one associated with abnormalities on MRI, so-called white matter changes. The symptoms in such cases would be variable. However, given that your MRI is not showing abnormalities, this is reassuring.
I do not believe your rash is due to a neurologic side effect, but it could be due to remicaide, as a side effect or allergy and also, Crohn's disease can cause a skin changes as well. Remicaide can cause some vision changes and tremor during the infusion, often associated with allergic symptoms. However, this is less likely if your symptoms developed 2 weeks after your infusion. All in all, it does not seem likely remicaide would explain your symptoms, this seems unlikely. However, as you may know, remicaide can cause an increased risk of infection, but you are on the right track since you had a lumbar puncture, which would show whether or not there is an infection. The twitches could be benign fasiculations, which are not an uncommon muscle twitching that occurs in response to stress, caffiene, anxiety.
In addition, Crohn's disease itself can cause neurologic problems, it can cause problems in the brain, peripheral nerves, or muscles. It can predispose to clotting problems, particularly during a Crohn's flare. With intermittent one-sided body symptoms, a transient ischemic attack (TIA, or what is commonly known as "mini-stroke") would be one possibility. If this is suspected, a work-up is indicated to make sure there are no clots being sent to the brain from the heart or blood vessels, and an aspirin or other blood thinking medication may be indicated. It sounds like you have been evaluated appropriately, but I do recommend continued follow up with your neurologist for continued evaluation and follow-up.
Thank you for using the forum I hope you find the information provided useful, good luck.