rblog

Today I spoke to my neurologist and got the news that the MRA was negative - which might sound like good news, but actually is a bit more complicated.

Let's start with a review of where we stand. The thoracic MRI indicated something that appeared to be an Arteriovenous Fistula (described in an earlier post). However, it appears to be small and somewhat difficult to diagnose. But if I do have the AV Fistula in the location that it appears to be, then that would indeed explain my symptoms (I went over this with the doctor in detail). Thus, doing something like a spinal tap (i.e. lumbar puncture) would not make any sense. But since nothing showed up on the MRA and it the fistula is too small to be detected by physical exam, we would have to do something more invasive to find it.

That "more invasive" option is a spinal angiogram (or thoracic angiogram). Which involves Arteriovenous threading a catheter up from an artery in the groin up to the aorta (guided by x-ray and contrast imaging). Each of the approximately 12 arteries that lead to the spinal cord must be inspected (e.g. contrast injections). Many images are taken during this procedure, so the patient is required to be very still (local anesthetics are applied to the site of the catheterization). The artery that is used is a fairly large artery and this presents some risk of internal bleeding and other complications.

There is also no guarantee that the Fistula will show up on the angiogram. Should it appear, treatment is usually the embolization I discussed in my prior post.

So the decision (as yet unmade) is whether to go ahead with the spinal angiogram or to wait six months to see if we can spot the AV Fistula using another MRA. This would avoid the risk of the angiogram. Of course, it is better to treat things earlier, but that has to be balanced against the risk of the angiogram that may not yet show anything. Note: I don't yet have solid data on how long a spinal angiogram takes - but one writeup indicates that it can last for as long as 2 days, due to limits as to how much they can do at any one time.

Reading materials:
1. Spinal Angiogram - non technical
2. AV Fistula - somewhat technical, more accurate description of what I have - focus on "Type 1 Spinal AVM: Dural Arteriovenous Fistula" section.
3. A technical review of AV Fistulas and how they are diagnosed
4. MDCTA - Multi Detector row Computed Tomographic Angiography
This is a write up of a new technical for evaluating spinal vasular malformations. It is a small study, three cases of spinal dural AVF (which is what I may have) and one case of perimedullary AVF. It worked in two of the three spinal dural AVF - but not in the third, probably due to the small amount of shunting blood at the fistula. Conclusion is that MDCTA provides useful information for the surgeon in the treatment of the spinal dural AVF... MDCTA should be considered as a choice of investigation in the evaluation of spinal AVFs.
5. Another article on MDCTA as a possible adjunct to catheter angiography. This one concludes that MDCT angiography correlates well with catheter angiography in diagnosing spinal dural AVFs. It might also play a role in shortening the length of a catheter angiography. Disadvantage is the use of ionizing radition. This article also states that catheter angiography is required before embolization.
6. I also found a really good writeup describing how to actually perform a spinal angiogram - but I don't think anyone would actually want to read it.

The next steps for me are to talk to some of my physician friends and see what they recommend.

Questions I will pursue (based on algorithm below)...
1. Did the MRI show a high T2 signal - this is very strongly correlated to spinal dural AVFs that show up in a spinal angiogram. If no T2 signal, we probably won't see anything on the angiogram, so why do it?
2. Are there other techniques that would be less risky/invasive than the catheter angiography - in particular the MDCTA or the onld supine/spinal myelogram (I only hold out hope for the first).
3. Let's say we knew it was a spinal AVF, would we have to do a angiogram before we could treat it? (I believe the answer is yes).
3. What would we do if the angiogram was negative - would it be a wait and see approach? I assume yes.
4. How long does the angiogram last? Can a general anesthetic be administered?

And now, my algorithm is finally clear - for those that can any type of computer code, it should be clear...
if (T2 = Low) {
//angiogram may not find anything
if (MDCTA available) {
// Try MDCTA
if (MDCTA() == found) {
treatment();
} else {
wait();
} else {
wait(); //?
}
} else // T2 = High
if (catheter angiography required for treatment) {
catheter angiogram(general anesthesia);
if (found) {
treatment();
} else {
wait();
}
} else {
// Try MDCTA
if (MDCTA available) {
if (MDCTA() == found) {
treatment();
} else {
wait();
}
} else {
wait(); //??
}
}
}