Unable to have MRI

I have been experiencing headaches and dizziness over the past weeks. I also discovered that my pupils were different sizes with variable see-saw aniscoria (alternates eyes and occasionally same size). I was seen by an opthamologist who measured 1mm difference in my pupils and referred me to a neuro-opthamologist. I was evaluated by a neuro-opthamologist and the day I saw him my eyes were normal with no difference in pupil size. I was told that I had physiologic aniscoria and no further evaluation was neccessary. In light of my other symptoms, I am still going to get a CAT scan. I am concerned, however, because I have a defibrillator and am unable to have MRIs. It is my understanding that the CAT scan can not pick up certain things and I am concernd about a tumor being missed because I can not obtain an MRI. Can you please comment on the differences between a CAT scan and an MRI and how concerned I should be about not being able to obtain an MRI? Can you suggest the best way to proceed with getting a diagnosis given the complications of having a defibrillator?

Thank in advance,
Erica

[rumpled]

The CT and MRI are different yes but often CTs are used as a first scan. CTs use radiation - more of a 3D x-ray and MRIs use magnets to get pictures. They use different contrasts as well. I have seen it where they want both as they show different things but I would not fret - unless the lesion is super small, it should show up fine in a CT. I get MRIs as my tumors are on the pituitary and those are tiny and do not show up well on the CT. But I have had many of both.

I see a neuro-optho as well and I have a difference in my pupils at times - but 1mm is not considered significant. Depending on the location of your tumor, you may have to get visual field tests. That is important if they suspect a tumor - to see if it is pressing on the optic nerves at all.

Keep us posted on the CT. Have you seen an ENT to rule out other causes?