Q:  I've been reading a lot about Spect Brain Imaging. Do you think this is a valid modality?

Thank you,
Leslie
 

Dear Leslie --

The pictures below are SPECT scan (Single Photon Emission Tomography; a cousin of a CT scan). The one on the left is a patient with unipolar depression, and the one on the right is a patient with bipolar disorder. They look pretty different, right? Couldn't we use these to help differentiate people who will do better with an antidepressant, and those who might do worse?

               

If that was true, this would be an extremely useful tool. As you may know, that distinction is one of the most difficult than psychiatry right now. Some of our diagnostic distinctions don't matter very much (e.g. schizophrenia versus psychotic bipolar mania -- both of them are treated the same way nowadays, at least initially), but this one does: depending on what one concludes (unipolar versus bipolar) the treatments are nearly opposite.
                                                          
So if this scanning technique really could be used to differentiate these two conditions, as the pictures above imply, this could be a very widely sought tool. Why is that not the case?

First of all, to my knowledge there are no published studies on the use of SPECT scans to make this diagnostic distinction. Wait a minute: I just did a quick literature search to make sure, and found a few, although their quality may explain why I was not aware of them. For example, here is one article from 1998, comparing 10 unipolar versus seven bipolar cases (Tutus): in this series,the bipolar patients were not different than controls, although they were different from the unipolar patients. Here is a second study, more recent, 2004 (Benabarre): out of 18 patients with Bipolar I depression, nine had abnormal scans and eight did not. In the abnormal cases, scan differences were found in two different regions of the brain: some patients had one, some had the other, and some had both.

If this technique was highly useful for this diagnostic process, it would be under great scrutiny.  I think the results above suggests the reason why we have not seen more study of this approach.  It is not consistent enough.  If so, then going to a SPECT scan center, like the one from which I took the pictures above (BrainMattersInc), may not help in making an accurate diagnosis.  How would you know how to interpret a given result, when sometimes the condition you are looking for does not appear in the scan; or when it does, sometimes the abnormalities are in one place, but sometimes they are somewhere else --?

So that is my understanding at this point.  I could be missing something.  But you would think that someone who is offering you a laboratory test that costs thousands of dollars would have to show you good solid evidence that using their tests is better than proceeding without them.  That evidence should be published in a journal that requires a demonstration of good scientific procedure.  I am still waiting to see such evidence, although again, I may have missed something.  It particularly irks me that on a website for a SPECT scan center like the one above, you could search all over their website and have difficulty finding out how much the procedure is going to cost you. I've been there three times now and I still can't figure it out.

Dr. Phelps