Not a doctor and not saying what they are... however, white spots can occur on MRIs for a multitude of reasons and still be considered a normal MRI

make-up as previously noted
hair dye
old injuries to the head
aging
non-harmful cysts (like zit in the brain)
headaches
mild inflammation from any number of normal expected things, a recent cold, a mild sinus infection, allergies... you name it
a mini stroke (you'd be amazed at how many strokes people have without ever knowing it, it's not that big of a deal)

A normal MRI doesn't necessarily mean a "clear" MRI, it just means that there is nothing consistent with your Dx or anything life threatening found on the MRI at this time. If you get a copy of your MRI report from the radiologists it should also have some explanation for the white spots that are showing.

Something like "white matter found in the >>>> is/maybe consistent with >>>>" It might also include something along the lines of a possible dx even though the MRI is deemed normal because it requires further testing and a neurologists overview to arrive at a positive dx.

Like my own MRI was termed "normal", but said "normal lesion load for patients age, white spots found in the corpus callum may be consistent with MS diagnosis."

That meant that I didn't have a overly large lesion load given my age. It really came down to the placement of my lesions that assisted my neuro in sending me for further testing to obtain my dx. But it is very difficult to get a dx for MS strictly from an MRI.

A normal MRI is generally used to simply say, we don't think you have a massive tumor in your brain at this time nor do we think you are going to keel over in the next week. So it's really important to read the report thoroughly, perhaps more so than even looking at the images. There's too many things the images could mean to a layman, that the report is really where you get into the nitty-gritty of what is really being seen on your MRI by a qualified medical practitioner.

I even had a "normal" MRI with a fractured vertebrae in my back and bulging herniated disk. It was consistent with my symptoms and therefore "normal". It's pretty much exactly what they expected to see, and wasn't showing any major nerve infringement. So I wasn't paralyzed even though there was some nerve involvement with the spine, but I didn't have to go in for emergency surgery so it was "normal". Normal because I wasn't going to die or lose a limb, but there was certainly injury.

Same thing with my ankles and knees... Normal MRI's with torn and shredded ligaments and tendons. But it was still considered normal because it fell in the realm of my symptoms. And they basically saw what they expected to see, my ankle wasn't deformed in anyway leading to the pain I was feeling, the joints themselves were sound without any fractures or abnormalities, just the tears that were kind of known before hand, and that were consistent with the pain I was describing.

Not trying to worry you by any means that there might be some medical problem that the radiologist isn't telling you, and the neurologist is just going to drop it on you like a bomb. But it could be something, or it could be nothing. The neurologist will be your best bet for finding out exactly what it really is. And during your follow-up make sure he's willing to go over the images with you. I really dislike doctors who take the films out of the room to "review" them and then come back and tell you what they say.

Ask if you can go along if that's the case, so you can question the areas you're concerned about and have him explain what they are while you both are looking at the same picture. If nothing else, just tell them you're from Missouri the "Show ME" state .

In any event you definitely have some great questions to ask your neuro, make sure you're jotting all of these questions you're giving us to ask him/her when you go into see them again. In my experience the curious patient gets the answers, just don't say "I saw on WebMD..." Then they like to just pat you on the head and ignore you.