We did a CT Scan of the brain, do we need an MRI?? Would it help, and what could it show that a CT wouldn't?

Okay, we don't know what is wrong with my husband and I keep asking questions on here because I don't know what else to do. So please bare with me :o)

My husband has been having terrible headaches since September. The Dr.'s can't figure out what is wrong with him. Today he feels really weird, really week, a little sick to his stomach here and there, and his arms and legs kind of hurt.
For the past week he has pretty much had one constant severe headache. Today his head hurts, but not as bad as it has been.
We had a CT scan of the brain done last November. The Dr. was quite a jerk, so I don't know if they even looked at it good, all he said was "there is no mass or tumor, go home and drink some gatorade".
Would it be a waste of money to get an MRI of his brain?
What could it show that a CT scan didn't?
We don't have health insurance, so as much as I would just like to do it, we are already in debt about $10,000 trying to find out what is wrong with him.

First, find a doctor that isn't a jerk. That is crucial. If they won't take you seriously, just about any test will be a waste of money unless the problem is really obvious -- it's easy for a doctor to believe there is nothing wrong and then look at the results to "confirm" that belief. It's something all people do. Once you have a doctor who isn't a jerk, have THEM look at the CT scan just to be sure.

CT scans are based on X-rays. It's just a way of building up a 3D model of what is inside the body using a bunch of different X-ray pictures. X-rays tend to show dense things versus not dense things. So you see bones great on X-rays, but normal tissue (fat, muscle, skin, etc) all tends to look similar. So if there is a hard mass in the skill, a CT scan would catch it, but if it is a tissue abnormality, that might not show up. CTs can also be used with a contrast agent to show where blood is going (that is hopefully what you got, since I think that would be a lot more useful).

MRIs use a large magnetic field to basically make every water molecule in the body face the same way (water is a polar molecule) and then it stops producing the field and "listens" for the magnetic response of all the water molecules going back to normal. So MRIs are great for determining how much water is in different parts of the body, and so it tends to be better at viewing soft tissue abnormalities (which would seem to cover a lot of brain problems). Different types of tissues tend to hold different amounts of water, so it's easier to tell between multiple kinds of soft tissue.

Another scan to consider is a PET scan. Those show the metabolic rates of the tissues being scanned. This can often detect tumors (the metabolic rate is high in rapidly-dividing cancer cells), and can also determine if there is a low functioning area in the brain.

In the end, I have to put the disclaimer that I am NOT a doctor of any kind. So while I have an idea of the technical use of these tools, a doctor would have a much better idea of what might show up in one over the other. If the tests were cheap, you'd just go and get all three and be done with it. If you had insurance that made them cheap to you, it would also be easier to do a lot of tests "just in case". I really think you need to find a doctor you trust, and ask his opinion of how likely these tests are to be useful.

Finally, if he hasn't had a spinal tap yet, that's relatively cheap and can at least give them a measure of intracranial pressure (ICP), which could cause some of the symptoms you describe. High ICP isn't a disease by itself, but it's an important symptom that could give a doctor an idea of where to look. Of course, if the doctor is going to stick a needle into the spine, he might as well run some tests on the spinal fluid while he is there, which could be of diagnostic importance as well.

It's a shame in this world that getting proper medical care can mean going deeply into debt. It's a hard choice for anyone to make, especially when an expensive test may or may not show anything useful. Good luck!