Wednesday, October 26, 2011

Please Pay Attention As There Will Be A Quiz Following Today's Post

Stereoelectroencephalography

That's a nice word to start with on a day when I did not expect to have anything to post.

We will no longer refer to Spike's upcoming invasive test as "deep probes." 
Stereoelectroencephalography must be used instead. Ok, if you insist, you may use the droll acronym SEEG if your spell checker is challenged by words as common as
stereoelectroencephalography.

I happened across this word in one of the Cleveland Clinic brochures and knew I was on to something good. SEEG appears to be the diagnostic process utilizing the deep probes the neurologist mentioned yesterday.  As I guessed, these probes do provide 3D mapping of seizure activity. In fact, the various articles on SEEG insist that readings from a single probe cannot be used in the absence of other readings from other probes. That implies the multiple probes are, in fact, being used for 3D triangulation. I can't tell you how happy that makes me. Spike's procedure will, after all, get to use fancy math.

For those of you who would like to learn a little about SEEG, you can find a good layman's treatment at my.clevelandclinic.org/Documents/.../SEEG-Fact-Sheet-2011.pdf 

If that link doesn't work, google "a guide to stereoelectroencephalography"

However, for those of you who have no hobbies or social life, I highly recommend a subscription to the Faculty of 1000 Post-Publication Peer Review site http://f1000.com/ You will find all kinds of interesting reading there including links to the full texts of thousands of academic and practitioner medical articles. Oh joy! Christmas has come early this year! You can also stuff your stocking with treats from pubmed.gov and nih.gov

For the few unfortunate readers who may have a life outside this blog, I will summarize the information for you.


SEEG is the latest and greatest diagnostic tool used for localizing seizure foci in sneaky cases of epilepsy where the focal point refuses to stand up and wave at the MRI camera. Latest and greatest in the brochures perhaps but the crafty French began working with this in the medieval ages of the 1970s.


Electrodes (which I occasionally erroneously call probes) are inserted through holes drilled in the cranium as explained yesterday. The patient's brain waves are then monitored to determine the location of all this nastiness. 

Quick sidebar on that focal point. It is important to not only see where the clinical seizure (all that thrashing about) appears electrically but also where the seizure was triggered from. Sometimes the dang brain tricks you by starting a seizure in one point but hiding that point by causing all kinds of wild activity in neighboring areas. That's really nasty because the surgeon can go in and remove those super active zones and end up missing the trigger point altogether. It then continues to wreak havoc. Nasty, nasty, nasty.


But that's not going to happen with Spike.


The SEEG process continuously monitors brain wave patterns (like all EEGs) and the docs know to scroll back a bit and see where the villian trigger is hiding. Once they find him, he's toast. In fact, multiple studies at different centers reported finding the focal point 90% of the time. That's an incredible success rate. Even better, the success rate was the same regardless of whether the focal point was visible or not on MRI and all the other scans. So, in those cases where you just can't see the starting point, SEEG goes in, literally, and nails it almost all the time.


What are we waiting for? Drill baby, drill!


Not so fast. In fact, you have to slow down a lot. I don't know how the Frenchies did it in the 70s but with today's technology, the surgeons spend a whole lot of time prepping before pulling the trigger on the old Stanley.


First, they put little markers on the skull and do an MRI so they can hang pretty posters of the brain around the operating room and have a map of the head. That happens the day before the surgery. Then they perform an angiogram, snaking a catheter through a vein in the groin up to the brain and shooting some pretty dye all over the place so they can see the blood vessels. Good idea to miss those with the drill bit. They do a bunch of scans and put the head in a frame and all manner of other things - all with the sole purpose of figuring out where the heck they are when the put the probes in. Not only do they have to miss the blood vessels and other important brainy bits, they must also remember where the probes are after they close up so that they know what the SEEG is telling them.

If you're still with me, I'll make it real simple. The surgeon is simply making it possible to finally  draw the arrow that says "Cut Here" for the final resection.

And it appears to work. Most of the time. The studies I read all pointed to post resection seizure freedom in approximately 50% of the cases and major seizure frequency reduction in 90% of patients. That's pretty good considering the facts that these patients are a) drug resistant, b) have seizure foci that cannot be located well by all of the other tools and c) have failed to improve with all other treatments. Sounds like they are describing Spike!

Interestingly, when they examine the excised brain matter, they often find all kinds of conditions that should have shown up on the other scans. Who cares as long as Spike becomes Mr. Smooth.

One last cool fact. They can not only record electrical activity from the brain, they can also send electrical activity TO the brain. That's extremely important as you will all remember from biology class. Remember making the frog's leg twitch with a little jolt of electricity? Well, they can do the same with Spike. How cool will THAT look on YouTube! Not to mention the medical purpose of avoiding important brain bits of course.

Now before we all do a Happy Dance, let's look at the Sobering Realities:

1. 90% foci location success is not 100%
2. 50% post-surgical seizure freedom is not 100%
3. "seizure frequency reduction" in Spike could mean he drops from 50+ seizures a day to 20
4. There is a complication rate on the SEEG alone, not to mention the resection, of between 1% and 3.5%
5. I may be wrong on all of this

5 would be a real bummer but I have to allow at least the possibility that the Cleveland neurologist was  not referring to SEEG when using the words "deep probes." The doc just might have been referring to, oh I don't know, "deep probes" perhaps. Yeah. I found this one little item deep in some of the Cleveland material online.

vincent: How is this procedure different from depth electrodes?
Dr__Gonzalez-Martinez: When we implant depth electrodes, we are implanting about probably 3-6 electrodes in standard areas in the brain. SEEG is implantation of 15-20 electrodes in several areas in the brain. SEEG is an individualized method and each patient will have a different implantation.

Well, I'll have the SEEG please. If it's good enough for the French, it's good enough for Spike. After all, the French have a lot more experience with twitchy frog legs. Yeah, I'm an insensitive Dad but Spike still likes me, especially now that I can take him to Burger King again.

I promised a quiz and here it is: What does SEEG stand for?

Mice down, no scrolling back to the top allowed.

Answer: A possible answer to the frustrating search for Spike's seizure origin.

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