I have done a lot of reading about MS in the past 10 or more years, as in 2000 a neurologist (whom I’d gone to see for dizziness) basically told me I had it at my first appointment. Even though he knew that a year earlier I’d had an MRI that was (at the time) reported to be normal and a normal neurological exam.
He ordered a new MRI and then said, basically, that I DIDN’T have MS, or at least it was only a 5 percent possibility because only about 5 percent of people with MS don’t have brain lesions.
I found out LATER that BOTH of those MRIs were NOT “clean”–they did show small, scattered lesions. Those “tiny” lesions (often referred to as “punctate”) are quite infamous among people wondering whether they have MS–because they CAN be from MS but they can ALSO be from migraine, ischemia (tiny “strokes” due to high cholesterol, high blood pressure, and/or smoking), etc. So the doctors can’t really pin down the cause.
MS lesions TEND to be larger, appear in certain locations in the brain (such as periventricular areas, corpus callosum and I don’t know what all), and they tend to kind of oval, I think. However, a clear MRI, or a “nonspecific” one such as with those tiny scattered lesions, CANNOT definitively rule out MS. It’s rare but some people have MS with no lesions visible on MRI. Of course they do have lesions, but the MRI just can’t pick up the tiniest ones.
That said, doctors will usually tell a person they don’t have MS if their MRI only shows those small, nonspecific lesions. The exception would be (usually) if a person has a very clear CLINICAL case of MS, that is, highly typical problems such as certain problems with their reflexes, their eyes, etc. that just scream MS.
Tingling and twitching cut very little mustard for neurologists! No doubt because these symptoms are nonspecific, common, and can have many causes, including anxiety. People get them for no reason whatsoever–at least none that can be found. So neuros don’t worry about them.
To everyone here who’s been worried about MS, I would say, as long as you’ve seen a neurologist and they haven’t found anything suspicious for MS, don’t worry about it. The reason I worried about it for so long was because I DID have a lot of other weird things going on besides dizziness. I had a coordination problem, highly abnormal auditory evoked potentials (meaning damage to the acoustic nerve/brainstem) and other auditory testing was very abnormal, plus I had (and have had for 11 years) Lhermitte’s, odd sensations in my lower body when I bend my head down, which indicates damage to the cervical spinal cord and is very typical of MS. However, repeated MRIs have always shown only the “nonspecific” spots, and repeated neuro exams have not found abnormal reflexes.
A spinal tap is sometimes done when it’s unclear whether someone has MS, but in my case they were unable to withdraw any fluid despite multiple attempts even when guided by x-ray. Very disappointing.
MS can be easy to diagnose if it’s a classic case, but it can also be VERY, VERY frustrating and time-consuming, sometimes taking many years. This is because there is no one test to rule out or diagnose MS. It is a clinical diagnosis. A person can have no visible MRI lesions, a normal spinal tap, and still have MS. On the other hand, a person can have a brainful of MS-like lesions and yet have no symptoms whatsoever! In fact sometimes MS is discovered by accident when someone has an MRI for another reason, and MS is sometimes found in the brain at autopsy even though the person never had symptoms. Someone with very severe MS symptoms can have a clean MRI, while someone with a brain lit up like a Christmas tree can have only the mildest of symptoms.
I believe that if I did have MS, I would by now (11 years later) be having abnormal reflexes or some other big indication of it. But I don’t. I am having progressive trouble walking (cannot walk 2 blocks without stopping anymore) but that may be due to scoliosis. I do wonder about the Lhermitte’s and the abnormal AEPs, not to mention the widespread paresthesias, coordination problem and other things I’ve had over the years, but I know I am not going to get an answer. I had to diagnose myself with MAV to account for the dizziness, as doctors would just say it’s not this, it’s not that but they would lose interest in actually trying to diagnose whatever I DO have! And they never put any stock in my migraine questions–they don’t take it seriously when you don’t have the headache.
Well, that’s probably more than you wanted to know. 
Nancy