Saturday, November 5, 2011

Anatomical Preview

I have found this image of the brain helpful in understanding Spike's condition.

Fortunately, most doctors use images a bit more like this one.

Although this view shows the brain from the left side, it is a good representation of structure and I could not find an image from the right side.

Spike's seizures occur in the right frontal lobe. One of our big concerns is that some seizure activity could extend as far back as the motor cortex. Taking out any part of the motor cortex could affect movement and, in Spike's case, likely the left leg. Initial analysis of SEEG tracings indicated activity in that region. However, subsequent, finer analysis indicates that the activity MAY only extend as far as the supplementary motor cortex area. In this split view you can see the area we believe is troublesome for Spike. It is the purple zone in the background half of the image.

All of the tests apparently verify that the area in front of the purple (the right frontal lobe) is affected. The question now is: does the epileptogenic zone spread only as far back as the supplementary motor cortex or all the way to the primary motor cortex. Apparently, for a patient of Spike's age and health, a resection that includes the supplementary motor area COULD result in no loss of motor function. The premotor cortex may also be affected (I'm not sure) but the primary area of focus right now seems to be along the upper part of the mesial area which means, in this case, the top leftmost area of the right frontal lobe - so, up against the split of the two hemispheres. Got it?

The area also appears to be deep rather than on the surface. What THAT means is that you get another picture!

Think of this as a slice of the primary motor cortex running from the middle of the brain to the outside. (The image shows the left side so just reverse the order of toes and fingers.) That leg hanging there refers to the area of the motor cortex that controls the, you guessed it, leg. That's the area of interest for Mr. Spike because it is closest to the hemispheric divide and the various EEGs are pointing just in front of that as the trouble zone.

All of this is complicated a bit by the fact that you want to remove the area triggering the seizure without removing any additional area that may be throwing signals as a consequence rather than cause of the seizure. The problem in Spike's case is all of the areas are so quickly involved that it is difficult to tell if everything is firing at the same time or if there is a consequential spread. Most of the evidence appears to be pointing to a large area triggering the seizure. That's not the best outcome but the area of concern, while not small, does appear to be slightly smaller than initially feared.

As if that is not enough to confuse the issue, the doctors also need to take into account the fact that functional areas, while similar amongst different people, are not in exactly the same place, For instance, it is hard to tell precisely where the motor cortex begins. So, while the electrodes currently in Spike's head tell the doctors where the seizures occur, they do not tell exactly what that region controls. Apparently, the brain is not color coded like these diagrams.

Finer analysis of higher frequency readings is now underway to further localize the seizure zone.

Fortunately, the SEEG electrodes can be used actively rather than just passively picking up signals. You can send electricity INTO the brain. Well, you can't but the doctors can. I suppose, technically, you could but I'm not going to let you. When the doctors send a little current down the line, Spike will react by moving a finger, kicking a leg, telling a story or howling at the moon. By observing exactly when these various actions occur, they can better map the specific functional geography of Spike's brain. That little jolt test is scheduled for Monday morning. Should be fun to watch. Actually, it will be extremely stressful to watch because his arms and legs WILL move but we won't know whether those movements are good or bad signs until the doctors gather in a backroom and finish their analysis. When they finally come out, they will have a 3D view of Spike's brain function superimposed on his seizure zones. At last, the X that marks the spot will have been drawn.

At that point, a final recommendation will be given along with, I hope, some view of the likelihood of both seizure freedom and functional loss, if any. Of course, this being Spike, the likelihoods are more difficult to determine because of the location of the seizures in the right frontal lobe.

So where does all of this leave us? Waiting, of course, but with a little bit more optimism than yesterday. That optimism could grow or quickly fade depedning on the results of both high frequency SEEG readings and, very importantly, the results of the functional mapping on Monday.

The next 36 hours will not add much to our understanding of Spike's prognosis and will therefore just crawl slowly. Sometime late Monday morning, we will suddenly receive a burst of information and have to make the call on going forward with surgery if the doctors feel it is likely safe and effective.

One last fun image. This depicts the proportion of the motor cortex used by the various areas of the body. I have included it for no other reason than its innate coolness.

Images in this post come from the following websites who have copyrights but allow fair use of the images:

1 comment:

  1. My wife (and 3 of her crani-buddies) have talked about getting T shirts that say:

    I had brain surgery--
    What's your EXCUSE?