Penumbra

I just read an interesting story about a new treatment for occlusive strokes.

The device is known as Penumbra and is being put out by the company of the same name Penumbra, Inc.

From the story I read, and from my brief visit to the company website, it looks like it might have promise to treat some stroke victims who otherwise would be sort of out of luck.

Basically, from the description, this is a catheter type device that is threaded into the femoral artery (The great big artery in your groin that feeds blood to your leg), and is worked in retrograde fashion up the aorta and then into the appropriate arteries (carotid, etc.) until reaching the site of the blocked artery inside the skull. It then acts basically like a vacuum cleaner and sucks out the blood clot that is blocking the artery and causing the stroke.

So a little background on strokes is in order.

There are basically two main types of strokes, Occlusive and Hemorrhagic.

The names are pretty descriptive.

In an occlusive stroke, an artery feeding a particular part of the brain is occluded, cutting off blood flow to that part of the brain. This is almost always caused by a blood clot forming in the artery at the site of a ruptured plaque (due to arteriosclerosis…i.e. “hardening of the arteries”), or forming somewhere “upstream” from the site of the blockage (in the heart or a larger artery), breaking off and then floating downstream until it gets to a small enough artery to get stuck and block it. (I say “almost always” above, because there are some much less common causes that I won’t go into in this post.)

With hemorrhagic stroke, an artery feeding some part of the brain actually ruptures and blood begins to leak out into the surrounding brain tissue. This is also frequently a result of arteriosclerosis.

A major contributor to arteriosclerosis is smoking. If you are a smoker, did you see my last post urging you to quit? If not, go look at it, and then QUIT SMOKING!

The particular symptoms one experiences from the stroke, such as facial drooping, or weakness on one side of the body, etc, are dependent upon which area of the brain is being affected.

Anyway, the first type of strokes described, the occlusive strokes are the ones this device is aimed at.

Currently, the main emergency room (E.R.) treatment for these strokes involves the use of a clot-buster medication called tPA (which stands for Tissue Plasminogen Activator). This stuff is given intravenously and can dissolve a blood clot.

Sounds great right? Well, it’s actually not so great.

There is a big list of contraindications for giving tPA. This stuff is not without risk of serious complications. The main one being undesirable bleeding. The first thing on the list is the one which keeps the vast majority of patients with occlusive stroke from receiving tPA and that is time from onset of symptoms. If tPA is going to be used, it must be given within a maximum of 3 hours from the first onset of stroke symptoms.

During my 3 years of residency training, I saw a LOT of folks come into the ER with occlusive strokes. I, and the rest of my colleagues in training were always itching for the opportunity to use tPA in a stroke patient. On average only about 3-5% of folks with stroke actually make it to the E.R. in time to be a candidate for tPA. Of all the stroke victims I saw, only one…that’s right, only one in 3 years time….actually arrived at the E.R., within 3 hours of symptom onset. Unfortunately, this patient also didn’t get tPA because she got excluded by one of the other exclusion criteria on the aforementioned big list.

So, there’s two messages here.

The first and most important one is IF YOU START HAVING ANY SYMPTOMS THAT MIGHT BE A STROKE, GET YOUR BUTT TO THE E.R. IMMEDIATELY!!! Don’t sit around the house like Cleopatra (the Queen of De-Nile) hoping it’ll just go away on it’s own. CALL 911 RIGHT AWAY!

The second message is that the first message is largely ignored, and even when it ain’t ignored there’s often other criteria preventing the use of tPA, so maybe that stuff ain’t so great after all.

Here’s where it appears Penumbra may come into the picture to make things a little better. Penumbra has a somewhat longer time-frame within which it can be used. Unlike tPA which has to be used within 3 hours of symptom onset, Penumbra has an 8 hour window.

It seems obvious to me that the device gets it’s name from the concept of the “Ischemic Penumbra“, which in a nutshell is the area of brain tissue that is not getting adequate blood flow due to the occlusive stroke, but which hasn’t actually died yet…i.e. the area of brain tissue this device aims to save.

Remember however, the name is Penumbra, not Panacea.

While an 8 hour window is obviously better than the 3 hour window tPA has, I suspect there will still be a heck of a lot of folks who won’t get to the E.R. in time. Certainly though, the numbers should still be better than with the tPA timeframe.

There’s also the issue of problems associated with reperfusion. In the world of medicine, it’s nearly impossible to find any treatment for any condition that doesn’t at least have the potential to make things worse, and Penumbra is no exception.

When you cut off the blood flow to an area of tissue for any appreciable length of time, there is serious potential for a condition known as reperfusion injury to occur if blood flow is restored. (Warning, if you follow that link, it’ll take you to an article that uses a lot of twenty-five dollar words and may make your eyes glaze over. It’s a pretty interesting read however if you can stand the medical jargon). Basically reperfusion injury is a pretty complex inflammatory type of process that in a nutshell can cause further cell death. So, by restoring blood flow, there is the potential to actually kill more brain tissue. That eye-glazing article talks about some current research trying to prevent that.

The other big potential problem associated with removing the clot has to do with the structural integrity or durability of the artery wall. If you’ve got an artery that is compromised by long-standing arteriorsclerosis, it is at increased risk of tearing open when blood pressure is restored to it. Further, just like the brain tissue that has been starved of blood flow, the walls of that artery are also composed of cells that have been potentially injured by the lack of nutrients and oxygen due to the clot upstream. As a result, the arterial wall is now potentially quite weak and prone to failure.

So what happens if the arterial wall ruptures? Well, at that point, your occlusive stroke has just evolved into a hemorrhagic stroke.

So, as the msnbc article discusses, Penumbra sounds like its got a lot of potential to serve as one more tool in the E.R. toolbox, but it is not without some potential pitfalls.

So, here’s the two questions that immediately popped into my head when I read about Penumbra.

1. Has the company looked at all into using this or a similar device for treatment of occluded arteries elsewhere in the body, such as for treatment of blocked coronary arteries in heart attacks for instance?

2. When a person suffers a hemorrhagic stroke, one of the main complications that can occur is that the growing pool of blood that is pumping out of the ruptured artery and into the surrounding brain tissue can cause tremendous pressure to build up inside the skull. This pressure can do great harm to the soft and fragile brain tissue. Often times, such a condition results in a trip to the operating room where a really smart fella known as a neurosurgeon ends up cutting a hole in the skull (known as a craniotomy) to relieve the pressure and remove the pool of blood. Does Penumbra have any potential to be used in hemorrhagic strokes to suction this pool of blood out from the inside, rather than the patient having to undergo craniotomy?

I know this is a pretty new blog, without a lot of exposure yet, but it is indexed on Google and Yahoo. Perhaps somebody from Penumbra, Inc. will run across it and can leave some comments.

I’d appreciate it, as I suspect the other readers would as well

How ’bout it folks?

…Sam

6 Responses to “Penumbra”


  • Hi Dr. Sam,

    I like this post; you’ve got a great way of explaining things like a normal person would. :) However, there are still some things that I think you assume us non-medical folks understand when we read this.

    Like, for example, what’s the line about Its Penumbra, not Panacea… What? What’s panacea?

    Or, your paragraph explaining Reperfusion; I still don’t really understand your explanation. Does the restored blood flow cause inflamation in the brain and thereby kill off more blood cells? I’m confused.

    Finally, you talk about arterior sclerosis like everybody knows what that is. In most of your blog, you don’t do this–you even define what “ER” means! But here, you breeze over the word like its something we all use everyday. At least for me, not so much.

    Thanks for all your help on this. My grandpa had a stroke a few years back and so I find postings like this very helpful. Keep it up!

  • Hi Jesse,

    Thanks for the great feedback!

    You’re right. I try very hard to avoid using jargon without explaining it in “regular people” terms, but sometimes I fail in that.

    That’s why I really like this comments ability in wordpress, so that when I blow it, folks can call me on it and give me a chance to better explain things.

    I’ll try to answer your specific questions in a second, but first I’ll go off on a bit of a philosophical self-improvement tangent.

    The point you bring up leads to a very important concept when it comes to reading and learning. A good habit folks should discipline themselves to pick up is one of never simply glossing over words they don’t know the definition of or understand.
    Anytime you are reading something, especially a document where you are trying learn something new and you come across a word or phrase you are not familiar with, you should make it a personal policy to go no further with what you are reading until you find out just what that word or phrase means.

    If you do what most folks do and simply go on with your reading, you are usually dooming yourself to not being able to gain a good understanding of the material you are reading.

    Folks, make this a firm habit for the rest of your life. It will produce tremendous rewards. I guarantee it.
    Anytime you are reading something (such as my blog, or a school textbook, or whatever) and you come across a word or phrase you don’t understand. STOP! Go no further until you find out what that means!

    Open a dictionary, do a Google search, ask someone else…..whatever, but go not further until you resolve this issue.

    Okay, enough pontification for now.

    Now to answer the specific words you brought up.

    Panacea basically is a term that means a “Cure all.” It has its origins in the Greek word “Panakeia.” In Greek mythology, Panacea (or more accurately Panakeia) was the name of the Goddess of healing. She was one of the daughters of Asclepius,
    the God of Medicine.

    That funny little stick wrapped by a serpent (snake in this parts) that you may have seen at times, used to represent medicine is “The Staff of Asclepius”.

    Interestingly, in many cases, particularly in the U.S., the somewhat similar, but less correct symbol known as the “Caduceus” is used. This is the one that has a rod wrapped by two serpents (not one serpent like the Asclepius rod above) and has a pair of wings.

    The Caduceus actually is the symbol of the Roman God Mercury (who is the same guy as Hermes in Greek mythology). Mercury/Hermes is not the god of medicine, but rather was the messenger of the Gods, and ruled more over the areas of commerce, travel, eloquence, magic and theft.

    Although you may often seen the Caduceus linked with the medical profession, especially here in the U.S., the Staff of Asclepius is more proper.

    Interestingly, the symbol used to represent veterinary medicine and the veterinary profession is the Staff of Asclepius with a large letter “V” superimposed upon it.

    So anyway, that’s a longwinded way of saying that Panacea means “Cure All”

    Your next question about reperfusion is quite frankly a big can of worms. This is a subject that is massively complex and is a big area of medical research.

    In a nutshell, the answer to your question appears to be “Yes.” The restored blood flow does contribute to a big inflammatory reaction and plays a part in further cell death.

    This subject is too complex for me to fully explain here, but basically, these cells that have been deprived of oxygen appear to form a bunch of chemicals known as free radicals. These are very damaging to proteins in the cell membranes and to the cells DNA. They seem to create an environment that is conducive to triggering an inflammatory response. When blood flow is returned it carries with it a bunch of white blood cells, which respond to this environment by releasing all sorts of inflammatory chemicals of their own.

    All of this seems to create a sort of toxic soup and starts a chain reaction that starts killing cells. As these cells die, they release even more chemicals that perpetuate the reaction.

    This phenomenon isn’t something that only occurs in the brain. It can occur in any tissues that are deprived of blood flow for a long enough period of time.

    Again, this is a very superficial explanation and this is a big area of medical research.

    The take home message isn’t so much about what reperfusion injury is but rather that it can and does occur, and is a potential bad consequence of Penumbra, or any other method of similarly restoring blood flow.

    If you’re interested in a more detailed explanation, as well as one of the areas of research into ways to modify this reperfusion injury phenomenon, hit that “reperfusion injury” link in the original post above.

    Finally, as mentioned in the post above, arteriosclerosis is basically hardening of the arteries. In fact this is a medical term, which like most medical terms, is simply created by combining other words from either Greek or Latin.

    In this case, you have the Greek word “Arteria,” which means artery, combined with the Greek word “Sklerosis,” which means hardness. Combine them and you get Artery-Harness. Arteriosclerosis means hardening of the arteries.

    There are actually several forms of arteriosclerosis, but the most common is atherosclerosis, which is a hardening, caused by formation of an atheromatous plaque in the artery wall.

    Whoa!!! What the heck is an atheromatous plaque???

    Again this is a somewhat complicated subject, and in spite of how absolute and confident most in the medical profession come across about this topic, I’m personally convinced that there is still a whole lot of stuff we just don’t know yet.

    In a nutshell, what happens is that over time the walls of the artery can become damaged. This is particularly true in areas of arteries where there is increased pressure, and turbulence or damaging forces being exerted against the arterial wall.

    In your bodies circulatory system there are two sides: the venous system and the arterial system. The venous system is a low-pressure system that carries blood to the heart from parts of the body. The walls of veins are relatively thin and flexible. Again this is a low-pressure system. Rather than having to “Push” blood against any sort of resistance, the veins are more passive. They essentially have their blood “Pulled” from them by the heart.

    The other side, the arterial side, is basically the opposite. It is a high-pressure system. The heart has to “Push” blood through these arteries into all the tissues in the far-reaching parts of the body. The arteries have thick muscular walls that are much less flaccid and flexible as compared to the veins.

    When we are born, these arteries are new and are in pretty good shape. Over the course of a lifetime however, they are subjected to years of high pressure and abuse, and eventually can start to show signs of wear.

    Just like an old hose laying in your yard for years, exposed to the elements, the walls of the arteries over time can start to become increasingly stiff and brittle.

    If you had a super powerful microscope and could look at the inside walls of these arteries, you’d see that small cracks start to form. Triglycerides, fats and bad cholesterol in your blood can leak through these cracks so that they are no longer in the blood stream, but rather become located within the wall of the artery.

    Apparently the body doesn’t much like this. It seems to recognize this stuff in the arterial walls as foreign…as an enemy contaminant that must be dealt with.

    Special white blood cells (there are several different types of white blood cells, but they are all sort of like your body’s army or police force…they go marching into bad places and deal with attackers such as bacteria, viruses, etc.) move into the area and start to gobble up all this fatty stuff. At this point they become known as “Foam Cells.” This is because they appear foamy when they are all filled with this fatty stuff.

    Well over time, through a bit of a complex system of chemical reactions, these cells begin to become calcified and hard.

    Another type of cell called a fibrocyte moves into the area and starts to build a fibrous cap over the foamy area. This is basically a thick hardening wall that walls off the foam cells. The resulting structure is known as a fibrous plaque, or atheromatous plaque.

    Over time this process continues and expands for years and you end up with a situation where the arterial wall becomes increasingly hard, brittle and thickened. As it thickens, it can start to occlude the lumen of the artery (which is the hollow part inside through which the blood flows).

    It’s sort of like the drainpipe from your kitchen sink. As years and years of grease, and soap, and coffee grounds, and rust, etc build up on the inside walls of the drain pipe, the lumen….the hollow part inside…becomes smaller and smaller, and eventually your drain starts draining pretty slowly and it’s time for some liquid plumber.

    If something happens and causes one of these plaques to rupture…i.e. the fibrous cap breaks open….exposing the underlying inner layers, it can fool the body into thinking there is a wound that needs to be healed.

    The first step of this healing, just like when you cut your finger, is the formation of a blood clot.

    On your finger, this is a good thing as it stops the bleeding. On the inside of a small artery feeding a vital part of your body, such as part of the brain or heart for instance, this isn’t such a good thing.

    The clot can cause the artery to become blocked…in the heart this is what typically causes a heart attack. In the brain, it causes an occlusive stroke. This same sort of thing can actually happen anywhere in the body however. It could kill part of your intestines, or a kidney, or your big toe.

    Again, think of your kitchen sink. If you’ve got a drainpipe that is brand new, the lumen is nice and big. Water flows through it easy. If you drop some food scraps down there as you’re cleaning your dishes, it’ll probably just go right on down the drain.

    If you’ve got an old drain pipe however that has a thick build-up of gunk on the inside and as a result a small lumen, well than that little bit of food scraps you try to flush down the drain, might just be enough to completely block it off.

    A blood clot on the inside of your artery can do the same thing. This is not something you want to happen.

    With your sink you can try some liquid plumber. With your artery, it’s not so easy. tPA and Penumbra are sort of an attempt to come up with a Liquid Plumber like solution.

    As mentioned, this is still a big area of medical research and we don’t really know as much about this stuff as we’d like to think we do.

    It used to be thought that the main culprits were the old mature plaques. Recent research however is starting to lead us to believe that it may in fact be the young immature plaques that are actually the most dangerous and prone to rupture and cause a blood clot to form.

    In any case, there are a lot of things that seem to contribute to formation of these plaques and this hardening of the arteries. Age, Gender, and Heredity seem to play a big role. There’s not too much we can do about these things.

    Other factors however, we can exert some control over. These include things like smoking, high blood pressure, high triglycerides and bad cholesterol, high blood sugar, sedentary lifestyle, etc.

    So, eat right, exercise, and DON’T SMOKE! (Have I mentioned not smoking before in this blog???)

    I know this was a bit longwinded, but I hope it helps.

    Let me know if you have other questions, etc.

    Cheers!

    …Sam

  • Dear Mr. Sam,

    I am from india, currently working in Melbourne, Australia.

    My grand father is in india. He cannot walk. He is retired government official. Doctor said he is having blood clots in brain and these can be dissolved only through medicines.

    In an indian daily new paper i read an article on this penumbra device. Can these blood clots be removed with this device.

    Is this treatment available in india or australia. If you are aware of this, could you please provide us more details.

    Regards,
    Chandra.

    ###

    Hi Chandra,

    I’m really sorry to hear about your grandfather. I am not sure if he would be a good candidate for the penumbra device or not, nor am I sure whether or not this treatment is available in India or Australia.

    Typically, with regards to disolving clots with medicine, time is a big factor. Typically, a patient must receive this treatment within the first several hours of onset of symptoms. (Traditionally, the recomendation has been that the treatment must be started within the first 3 hours of symptom onset, but some recent research is pointing towards expanding this window a few hours, possibly up to 6).

    I’m not sure about time frames for use of the Penumbra device and to be honest I haven’t done any reading about this device recently.

    In a nutshell, probably the person most qualified to answer your questions will be the physician treating your grandfather in India.

    I truly wish the best for you and your family and hope that my answer here has perhaps helped in some small way.

    Sincerely,

    Sam

    ###

  • Thank you for your prompt response sam.

    Regards,
    Chandra

  • bove coll bittercreek salvietti nino rufino aud parely snappish

  • I’ve been exploring for a little for any high quality articles or weblog posts on this sort of area . Exploring in Yahoo I at last stumbled upon this website. Reading this info So i’m happy to convey that I have a very just right uncanny feeling I found out just what I needed. I so much without a doubt will make certain to do not disregard this web site and give it a glance on a constant.

Leave a Reply

Powered by sweetCaptcha








Unless otherwise indicated, all content of drsamonline is to be considered copyrighted material with full protection under the law. Nothing on drsamonline, either implied or otherwise, should be construed as indicating the establishment of a doctor-patient relationship, nor as an endorsement of any particular medication, test, or treatment. All content is for educational and entertainment purposes only. It should not be used in any way for diagnosis or treatment of any medical condition and should never be used as a substitute for examination and treatment by your own personal physician. Please send email to drsam@drsamonline.com to report problems with this website . Thanks.