Tag: Strokes

A Brief Introduction to an Amazing System

Two main sets of arteries feed blood to the human brain. At the front of the neck are the left and right common carotid arteries. The common carotids divide into the external and internal carotids. The carotid arteries are big, as far as arteries go, at about six millimetres in diameter for the average adult, and they account for about eighty percent of the total blood supply to our brains.

At the back of the neck, we find the left and right vertebral arteries—the verts. These major arteries run from a point behind the collarbones, up and through the vertebrae in our neck, and into the back of the brain. The verts originate from a junction with the subclavian arteries, another pair of large arteries that deliver blood into the arms. The verts are smaller than the subclavians, at about three millimetres in most adults.

As I’ve mentioned before, I look at medical subjects from a strictly layman’s perspective. One aspect of the arterial system feeding the brain that I find fascinating is the amount of redundancy that is built into it. In most people, the left and right vertebrals do the same job. The two separate arteries meet up in the back of the skull to form the larger basilar artery. It is the basilar artery that supplies the remainder of the blood to the brain, about twenty percent of the total.

Redundancy extends further than just between the left and right vertebrals. It also includes connectivity between the two sets of arteries feeding the brain, the carotids and the vertebrals. At the base of the brain, where the various arteries come together, there is a circle of connections between the carotid and vertebral arteries. This arrangement of communicating arteries is called the Circle of Willis, named for Thomas Willis, an English doctor who discovered it in the seventeenth century. Several other arteries meet up in the Circle of Willis and then take blood away to other parts of the brain.

The reason for the Circle of Willis is quite simple and elegant. If any of the main arteries is blocked, or occluded, then the parts of the brain that depend on the blocked artery can still get blood supply. In other words, blood can flow around the circle to get to its destination by another route.

Not the Circle of Willis

There can be differences in each person’s arterial connections, and many people have an arrangement other than a textbook Circle of Willis. This is what a neurologist would refer to as an “incomplete Circle of Willis”. It doesn’t seem that having an incomplete Circle of Willis is necessarily a problem. Besides, there is no option to fix it, given the complexities involved. In other words, an incomplete Circle of Willis is likely something that would only ever be discovered in an autopsy.

So, why am I even writing about this?

I know from personal experience that having an incomplete Circle of Willis can lead to higher risks of stroke or other neurological problems.

Even if that weren’t the case, I look at this system from a chemical engineer’s perspective. And when I do, I can’t help but be fascinated by the perfection of the design for this most essential system.

Mine just doesn’t happen to be perfect.

Stroke Symptoms: Think You Know Them All?

Thanks to effective public awareness campaigns, many of us are familiar with the common signs of stroke. Think of the television ads that show us what to look for if we think someone is having a stroke.  The mnemonic “F-A-S-T” reminds us to look at the Face (is it drooping?), Arms (can you raise both?), and Speech (is it slurred?), and to waste no Time in getting help.

This checklist is a potential lifesaver because when it comes to strokes time is of the essence. But there’s more to the story. That’s because there’s more to the anatomy of our brains than what can be incorporated into a simple memory jogger of stroke symptoms. I learned this the hard way.

I’ve written elsewhere about the fascinating system that feeds blood into the human brain. More on that very soon. (By the way, everything I write on medical matters is in layman’s terms.) In brief, there are two main sets of arteries, the carotids and the vertebrals. These arteries are found in the front and back of the neck, respectively.

The carotids are the workhorses, accounting for about 80 percent of the total blood flow to the brain. And these are the arteries that, if they get blocked or damaged, can result in the symptoms noted above.

In 2017, I began to experience symptoms that didn’t fall into the handy, F-A-S-T category. Over a period of two months, I had several episodes of vertigo. I saw strange artifacts in my field of vision. I had a sensation that my body had become disconnected from my brain.

Then, one morning in July 2017, I woke up feeling odd. The first things I did were look in the mirror (to see if my Face was drooping) and talk (to see if my Speech was slurred). They weren’t. I could move my arms and legs, although they felt strangely heavy and lethargic. Naturally, I concluded I wasn’t having a stroke.

The scans done later that day in the ER said otherwise.

It turns out I had developed a blockage in my left vertebral artery. These arteries, left and right, run from a point about the level of your collarbones at the back of the neck. They join up to form the basilar artery, which feeds blood to the back of the brain. The vertebrals account for about 20 percent of the blood flow to the brain, and when they are blocked, functions like balance and coordination, including visual and hearing coordination, are affected.

The blockage in my vertebral artery had probably been there for some time before it started to cause symptoms. Until my situation was eventually brought under control, after a lengthy stay in the Foothills Medical Centre stroke ward, I experienced a wide range of symptoms. I had my eyes and ears go out of sync, as if someone had gotten hold of the control knobs in my brain and started twisting them randomly. My tongue turned into a frozen lump. My arms went into jerky spasms. It was not pleasant.

The reason I’m explaining all this is to share what I’ve learned. While catchwords are helpful, they don’t tell the whole story. If you, or someone you care about, is having any of the above symptoms or a long list of others[1], get it checked out immediately. Symptoms that are caused by a blockage in the vertebral arteries can be deadly serious, just like those in the carotid arteries.

By the way, when I did some research into the F-A-S-T mnemonic, I found some recommendations that it be modified to BE FAST. Why? The B and E would include Balance and Eye trouble in the checklist of stroke symptoms. This version of the mnemonic certainly would have helped me.

[1] Other potential symptoms of “vertebral artery stenosis” include sudden falls, severe headaches, breathing problems, confusion, trouble understanding speech, incontinence, and more.

Running and Thermodynamics

In his book, “Running with the Pack”, philosopher Mark Rowlands makes some interesting observations about evolution. His essay, “The Serpent of Eden” starts by explaining the first and second laws of thermodynamics. While this immediately caught my attention as a chemical engineer, it may not resonate with everyone.

Basically, the preposition of the first law is that energy can neither be created nor destroyed; it can only be converted from one form into another. The second law states that any closed system (like the universe, or like us as entities within it) tends towards maximum disorder.

So, what does this have to do with running?

Well, Rowlands makes a rather neat argument that can be paraphrased as follows: because we evolved as creatures in a world where our stores of energy rely on us converting it from another source, there is a predisposition for us, as conscious beings, to focus on the competitive forces that allow us to continue living. Human beings are highly complex, closed systems, and for us to survive (that is, to avoid maximum disorder) we must compete for energy. And to do that, we must get it from another source.

Said another way, we tend to focus on those things that affect our ability to continue the competition… to stay alive. This is nothing more than the natural result of our evolutionary makeup. (Of course, the end game is predetermined, but let’s put that aside for a minute.)

Think about this. When you are running, and things are going especially well, what do you notice? Are you conscious of your heart and lungs and legs all doing their job efficiently, just as they were designed to do? No, of course not. They just get on with their job, and you enjoy the intrinsic benefits without even thinking about it.

Instead, what we tend to notice, as conscious, competitive beings, are the things that aren’t going so well. That niggling pain in your knee, or the stitch in your side, or any number of other ailments is what gets your attention. You do notice these things because, as Rowlands suggests, our brains have evolved to notice when things aren’t going well.

Rowlands gives further depth to his argument, with reference to the work of the great philosopher, Schopenhauer. And frankly, some of his observations are a bit depressing. Schopenhauer observes that because we are so highly evolved, with cognitive abilities like memory and anticipation, abilities that other creatures don’t possess, we are especially sensitive to our place in the grand thermodynamic scheme of things.

If the universe is destined to end up with maximum disorder, we might rightly ask ourselves why we bother. After all, what’s the point if we will all end up as worm food?

That’s where the Rowlands piece shines. He points out that as human beings, we have evolved as social creatures precisely because that improves our odds in the unrelenting competition for energy. The bonds that keep us together… mutual recognition, affection, love… can be seen as small bits of defiance against overwhelming odds, in a universe where the rules of the game are stacked firmly against us.

My advice is that the next time you are out running, you should spare a thought for the amazing confluence of conditions that had to go well for you to even be out there at all. The very fact that you exist is in defiance of the laws of thermodynamics, at least for the time being.

And the next time you are out running with your gang, give some consideration to them, as what Schopenhauer referred to as, “my fellow sufferers”. Since we are all in this together, it is only right that we should have some tolerance and patience with each other. As Rowlands says, “Every act of kindness we show to someone or something is a defiance of the spirit of the laws that made us”. Defiance may be futile, but it is still valuable.

On Racing and Recovering

Yesterday’s long run turned into a bit of a slog. Deb woke up with a pinched nerve in her neck, and I was feeling, well, crappy. Fatigued. Lethargic. We started with a walk, thinking that might be enough. Once we were warmed up, we slowly added some pace, but our run ended up being well short of what we planned to do, both in distance and pace. It was one of those runs best forgotten.

There may be more to the story than bad luck. You see, Sunday was two weeks on from a half-marathon that we ran in Vancouver. (Incidentally, it was the fantastic and well-organized First Half Half. Highly recommended!)

Although two weeks should be an adequate recovery period for a half, it got me thinking about how much downtime is enough after a race. I’ve always subscribed to an easy-to-remember formula that I learned years ago. It goes like this: treat yourself to one easy day for each mile you race.

Spelling it out, for a 10k race that means (more or less) a week of easy running; for a half marathon, two weeks; and for a marathon, a month.

There is a tendency to want to shorten these recovery periods. After all, if we had a positive race experience, why wouldn’t we want to get back in the saddle as soon as possible?

For me, that has usually not been an option. Inevitably, racing has taken more out of me than I’m willing to admit. Even after the immediate post-race soreness had cleared, the residual fatigue was too much to overcome in a few days. My effort in interval workouts or long runs during the recovery period, if I could do them at all, had to be scaled back significantly.

Add in the effects of aging, and whatever issues come along with it, and the rule-of-thumb recovery periods should get even longer. It makes sense that we aren’t as quick to bounce back as we used to be.

So, whether or not our recent experience was tied to an inadequate recovery or just bad luck, it’s worth remembering that a race puts major stress on our bodies. In summary, we should always respect the need for a full recovery.