Rewired
Remember how early on in the book I talked about the “creeping paralysis” that had taken place that fateful day? Strangely, a year later I have noticed an odd physical event: sometimes I’ll have a persistent itch either at the joint when my right leg joins the abdomen or actually up on the right side of my abdomen and when I scratch it my right leg and foot twitch and jump. It is as though they have some bizarre new connection.
Years ago an employee of the phone company came to our neighborhood to do some work on the phone lines. About an hour after he left, my phone rang. The caller had the wrong number but what was weird was that she was attempting to reach one of my neighbors! Odd coincidence I thought. A while later the phone rang again. Another wrong number. Another caller looking for the same neighbor! And then it happened again! “A coincidence?” I thought. I think not! Turns out that in fact while disconnecting and reconnecting our phone lines the phone company lineman had plugged them in backwards! I wonder if that can happen in the brain.
And why is it that it can work around some damage (I can use my hand and arm normally again) but not other damage (i.e. this darned leg!). I made an appointment to see my stroke neurologist.
At the doctor’s office, after catching up, we pulled out the old photo albums and reminisced about my stroke. I wondered aloud why I had managed to regain use of my upper extremities and looking at my “pictures” he noted a plausible explanation: my brain had apparently reached the limits of its capabilities. (Not the first time, mind you. I’ve had that experience frequently over the years. Especially when it came to algebra.)
It seems that my cavernous malformation[1] is located along the left frontal lobe’s “motor speedway” (or for those of you brainiacs, the corpus callosum). According to the Oregon Health and Science University Brain Institute (my italicized comments added), “The corpus callosum (Latin for “tough body”—ironic, isn’t it? Not so tough as you thought you were, huh mister?) is a broad, thick bundle of nerve fibers in the entire nervous system, running from side to side and consisting of millions and millions of nerve fibers. (not just millions, but millions and millions!) If we cut a brain in half down the middle, (Why would ANYONE do that??!!) we would also cut through the fibers of the corpus callosum.” (Duh!) I prefer the motor speedway image.
The corpus callosum is in the middle of the brain just above the brain stem running, basically, front to back. Just a smidge above that is one end of the primary motor cortex which runs side to side perpendicular to the corpus callosum up over the cortex. Are you with me here? This primary motor cortex is otherwise known as the “homunculus” or Latin for “little man.” The homunculus is called that because it—sort of—resembles a little man lying on his stomach with his head twisted around facing outward, as if over a large round rock, only this guy is draped over the motor cortex of the brain. [2] It actually doesn’t seem very comfortable, at that.
Anyway, this homunculus is thought of as the “body within the body.” As the blog site io9.com puts it, “We all know what bodies look like from the outside. This cortical homunculus is how your brain sees your body from the inside.” There are actually two of them, one over each motor cortex. “Every part of the body is represented in the primary motor cortex, and these representations are arranged somatotopically[3]— the foot is next to the leg which is next to the trunk which is next to the arm and the hand. The amount of brain matter devoted to any particular body part represents the amount of control that the primary motor cortex has over that body part. For example, a lot of cortical space is required to control the complex movements of the hand and fingers, and these body parts have larger representations in M1 (the homunculus)[4]than the trunk or legs, whose muscle patterns are relatively simple.”[5]
In lay person’s terms, this little dude is pretty strange looking! His head and hands are much larger than—and out of proportion with—his legs and feet and correspondingly the sections of the brain that control those motor functions are also out of proportion. That’s because your hands are much more intricate machines than your dumb old legs and feet! To put it in perspective, the sections of the motor cortex that correspond to the feet and toes (each with only one section) are only about a third as big as those which correspond to the hand, fingers and thumb (each with its own section).
(Can I just say that in researching for this book I have encountered some pretty weird stuff out there on the Internet? For instance, there seems to be a whole community of homunculus followers out there—like some strange cult—who have written about this weird little man, created at least one Facebook page for him, even created animated videos about him! Some people just have way too much time on their hands!)
Anyhoo…all this is to say that upon closer examination of my MRI it seems that the cavernous malformation lays alongside this homunculus on the left motor cortex of my brain. (Remember…the left side of your brain controls the right side of your body. Confusing to say the least!). The bleed must have begun at Homunculus’ feet (hence that’s where I felt it first) and spread “eastward” past the legs, trunk, shoulder, arm, hand, and fingers stopping just short of my middle and forefinger and thumb. Which explains why those were the only appendages I could move by the time I reached the hospital. Another way to look at this is to imagine a paint can spilling: the paint might pool right at the point of the tip over and then depending on the terrain might spread out from there, getting thinner as it spreads until it finally stops.
What does all this mean? Well, the paint spill started at my foot. That means the greatest part of the spill was there and caused the most damage to my foot and leg. And quite possibly, this damage is just too great[6]for the super muscle known as the brain to fix. In other words, the circuitry there is fried. Specifically, the nerves controlling my peroneus longus and my flexor digitorum are toast! This renders those muscles weakened and unable to win the tug-o-war with the opposing muscles. Consequently, the outside muscle of my calf that pulls against the inside muscle of my calf allowing me to keep my leg straight when I walk and the bottom muscle of my foot that pulls against the top muscle of my foot allowing me to flex and extend my toes (and wiggle them in the sand) can’t pull their weight any more. Of course, there are probably other muscles—and tendons—affected which all-in-all makes “walking” impossible and “getting around” a chore.
[1] Did I mention before that months down the road from my stroke, when we had learned of this little appendage in my brain, my darling husband still thought it was a large hole?
[2]Turns out those brainy folks who studied and named all the parts of the brain that we know something about can be somewhat imaginative as well. It’s a little like ancient people seeing a face in the moon.
[3]Organized in a point-to-point representation of the surface of the body.
[4]My insertion
[5]www.brainconnection.positscience.com
[6]Or perhaps, not important enough to bother with, as far as my brain is concerned.