Can an MRI (with contrast) miss a brain tumor?

A few weeks ago the bridge of my nose and behind my right eye went numb and tingled. Right as this occurred, I experienced some diarrhea. The next day, I began to feel strange (out of body, especially when moving or driving) and experienced light sensitivity and floaters. The tingling went away after three days, but then I began to notice tingling in my legs (only when I am wearing jeans, which tend to be on the tighter side for me), and now when I press on the nerve inside my elbow my entire right arm will tingle. I feel as though I am walking in a cloud, and I have anxiety which doesn't help the problem (although I am convinced as is my doctor that that isn't what is causing this as others have suggested). I feel some slight cognitive dysfunction (some slight memory loss, strange feelings), and as I am falling asleep I have strange thoughts that I can't remember a few seconds later that make absolutely no sense in situations that don't exist. My legs and arms tend to fall asleep easily (especially while sleeping). I had a brain MRI with and without contrast two weeks ago and they found absolutely nothing. All that has showed up abnormal is my red blood cells, hemoglobin, and hematocrit, which the hematologist doesn't feel are related to this. One thing I should mention is that I had mononucleosis about nine months ago and about three weeks after my recovery I experienced some strange numbness on my cheek that stayed for a day and a half, although it was not accompanied by these other symptoms so i am unsure if they are related, although the tingling was similar. Any suggestions for me on the next step or any idea of what this sounds like? I am terrified of having some kind of brain tumor which my neurologist assures me is not an issue, but the doubts are lingering. I am extremely frustrated at the medical process and am looking for any help I can get. Thank you.

[rumpled]

The only tumors I know that can be missed are pituitary tumors - they need to be done a certain way which is called dynamic. Your symptoms frankly, and I am not a doctor, sound more nerve related or more auto-immune. That is not going to show up on an MRI and it requires testing like EMG and the like for the nerves and special tests for auto-immune. Have you ever seen a rheumatologist?
For the nerves, only certain neuros specialize in the testing. Not all of them can do it. Make sure you get copies of everything (which is sounds like you do already) and take someone with you to the appointment to tell the doctor - sometimes when it comes from someone else, they listen more - which is silly, but it sad but true.
Those are just ideas. I do not know. I just have been through a wringer myself.

[LivingInHope]

Were your H&H and RBCs high or low in their abnormality?

[samuel32230]

My h&h and red blood cells were slightly above normal. I was under the impression they were nerve related as well. I am scheduled for a nerve conduction test. I'll let you know how everything goes. Thanks for your help. I truly appreciate it.

[LivingInHope]

Did someone give you that impression that they were nerve related?   I think you should get re-tested to make sure it wasn't a lab error.

Red blood cells, hemoglobin and hematocrit can naturally be a little higher in men than women.  High altitudes can cause high hemoglobin and hematocrit- do you live in one?
There are at least a couple of meds that can increase hemoglobin and red blood cells- methyldopa and gentamicin- are you taking either of these?  

Also, have you had a transfusion, hemorrhage or burn lately, because that can cause a difference?  During and right after hemorrhage, both hemoglobin and hematocrit can be elevated.  Had any bleeding lately that you know of?

  I have an old book I'm getting my info from, A Manual of Laboratory Diagnostic Tests 2nd Edition by Fischbach.  

It says hematocrit increases can be found in erythrocytosis, polycythemia, severe dehydration and shock, "when the hemoconcentration rises considerably".  

It says high hemoglobin is "found in" "hemoconcentration of the blood (any condition such as polycythemia and severe burns in which the number of circlating erythrocytes rises above normal)", "chronic obstructive pulmonary disease" (COPD), and "congestive heart failure".

Increased values in red blood cells, my book says, can be caused by "extreme exercise and excitement".  And it says "counts obtained under these conditions are of doubtful clinical value."    

But it also says increased values can be caused by:
"1. Polycythemia vera
2. Secondary polycythemia (seen in  erythropoietin-secreting tumors, in renal disorders such as hypernephroma and renal cysts, and in cancer of the liver)
3. Severe diarrhea
4. Dehydration
5. Acute poisoning
6. Pulmonary fibrosis
7. During and immediately following hemorrhage"

[Steven76225]

Sounds to me a lot like anxiety.  Seek treatment for that and if the symptoms don't go away, work from there.