Rehab Cell

Physical Medicine and Rehabilitation

Aneurysms – causes, symptoms, diagnosis, treatment, pathology

Aneurysms – causes, symptoms, diagnosis, treatment, pathology

Learning medicine is hard work!
Osmosis makes it easy. It takes your lectures and notes to create a personalized study plan
with exclusive videos, practice questions and flashcards, and so much more.
Try it free today! The word aneurysm is based off the Greek word
aneurysma, which means “dilation.” And that makes sense because aneurysms are
abnormal dilations in a blood vessel. We officially label a bulge in a blood vessel as an aneurysm
when the diameter of that bulge is about one and a half times larger than the normal diameter
of the blood vessel. Aneurysms can happen to any blood vessel in
your body, like the aorta, the femoral artery, the iliac artery, the popliteal artery, and
cerebral arteries. They can also happen in your veins too, but those are less common
because blood pressure in veins is much much lower than in the arteries. There are two major categories of aneurysms,
true aneurysms and pseudoaneurysms. In true aneurysms all the layers of the blood vessel
wall dilate together. True aneurysms that balloon out symmetrically on all sides of
the blood vessel are called fusiform aneurysms whereas asymmetrically shaped aneurysms balloon
out to one side of the blood vessel. This asymmetrical shape usually happens because
for some reason one side of the blood vessel wall has had to put up with higher blood pressure
than the rest of the vessel wall or because the wall was weaker on one side to begin with.
Asymmetrical true aneurysms can be called either “saccular” or “berry” aneurysms. You can think of pseudoaneurysms as false
aneurysms as in they’re not actually aneurysms at all. They are caused by a small hole in
your blood vessel which allows blood to leak out of the vessel and form a pool of blood
that looks like a fusiform or berry aneurysm depending on where the hole is and how big
it is. The blood pools because the surrounding tissues act as walls that contain the blood
in one spot. Arterial aneurysms occur most commonly in
the aorta with about 60% of true aortic aneurysms happening in the abdominal section of the
aorta and the other 40% happening in the thoracic section. Of all the abdominal aortic aneurysms,
you can find about 95% of them just below the point where the renal arteries branch
off from the abdominal aorta, but above the aortic bifurcation. That’s because there
is naturally less Elastin in the walls of this part of the aorta than the rest of the
aorta. Aneurysms are caused by a weakness in the
blood vessel wall, so anything, really anything, that causes the wall to weaken can cause an
aneurysm. When a blood vessel wall weakens, it struggles to contain the pressure of the
blood pushing against the walls, so the diameter of the blood vessel lumen increases. On top
of this, tension on the blood vessel walls increases as the diameter of the lumen increases
thanks to LaPlace’s law, making the aneurysm diameter even bigger, creating this cycle
of continuous bulging. You’ve likely experienced this when you blow up a balloon. The first
breath into the balloon is tough, but the next several breaths are pretty easy. This
is why aneurysms usually get bigger over time, it’s because of this positive feedback loop. So what underlying conditions might weaken
the wall of blood vessels? Well one way is if all the layers of those blood vessel walls
don’t receive oxygen. Typically the cells of the vessel walls are able to get oxygen
from blood as it flows by, but in the first section of the aorta, where the walls are
super thick and muscular in order to handle all that blood pressure coming from the heart,
they need to have their own set of blood vessels that supply the tunica media and the tunica
externa. We call these special blood vessels vasa vasorum. In hypertension, the vasa vasorum can develop
hyaline arteriolosclerosis, narrowing their lumen, causing ischemia to the aortic wall,
and we end up with atrophy of the smooth muscle of the tunica media. Overall all this weakens
the aorta’s wall. The same thing can happen in blood vessels
without vasa vasorum if we have a bunch of plaque building up on the tunica intima thanks
to our friendly neighbourhood atherosclerosis. Oxygen just can’t penetrate all the vessel’s
walls. You see this type of aneurysm often in the
abdominal aorta, where blood pressure is high and the aorta walls are nourished by passing
blood. If you think about this it’s no wonder then
why both aneurysms and atherosclerosis share similar risk factors: usually people who are
male, are over the age of 60, who have hypertension, and smoke. If we look at tertiary syphilis, it affects
the vasa vasorum as syphilis causes inflammation in the tunica intima of the vasa vasorum (which
again are those blood vessels that deliver oxygen to the thick walls of larger blood
vessels), ultimately leading to a narrower lumen and restricting blood supply to the
vessel walls of the thoracic aorta, causing atrophy. By the way, the name for this vasa
vasorum inflammation is endarteritis obliterans. If you were to look at the vasa vasorum in
tertiary syphilis, you’d see the inflammation causes fibrosis and scarring on the walls
creating this cool to look at, but less cool to have tree-bark like texture. Other bacterial infections can also cause
aneurysms, which we label as mycotic aneurysms. The bacteria from an infection somewhere else
in the body can break off from the main infection and travel around in the blood. Usually these
embolic bacteria will get stuck in the intracranial arteries, visceral arteries, or the arteries
feeding the arms and legs. There the bacteria enter and weaken the blood vessel walls, leading
to, you guessed it, an aneurysm. Some of the bacteria that commonly cause mycotic aneurysms
are, and these can be tricky to pronounce, so bare with me, Bacteroides fragilis, Pseudomonas
aeruginosa, and anything in the Salmonella species. You’ll also see mycotic aneurysms
are a complication of infective endocarditis. But it’s not limited to just bacteria. Infection
from the fungi Aspergillus, Candida, and Mucor are also a common cause of mycotic aneurysms. Genetic disorders affecting your body’s
ability to properly form connective tissue like fibrillin or collagen also weaken the
blood vessel walls, so people with Marfan’s syndrome have weakened blood vessel walls
because the elastic properties found within fibrillin is impaired. And people with Ehlers-Danlos
syndrome are more likely to develop aneurysms because their ability to form collagen proteins
is disrupted. Alrighty then. So intact aneurysms are usually
okay, and don’t cause any symptoms. I say usually because the bulging blood vessel can
compress other organs or vessels around it. So if an aneurysm compressed a major vein
like the inferior or superior vena cavae, it could decrease the amount of blood returning
to the heart. Usually though the big worry with aneurysms
is the possibility that they might explode, or more like rupture, but it’s more fun
to say explode. When an aneurysm ruptures, it’s like having a water main break. Blood
is spewing out from the hole in the blood vessel and less blood is flowing downstream
to the cells that need it, which causes ischemia in that downstream tissue. In thoracic aneurysms specifically, a very
serious complication can occur if the aneurysm is right above the aortic valve. As the aneurysm
dilates, it pulls on the walls around the aortic valve preventing the aortic valve from
closing properly, and allowing blood from within the aorta to flow back into the ventricle
during ventricular diastole. This particular condition is called aortic insufficiency,
and can also cause a high-pitched brassy like cough because the left recurrent laryngeal
nerve which wraps around the aorta is stretched by that expanding diameter of the aorta. I
don’t have that audio clip for that brassy cough sound, but it’s pretty distinct when
you hear it. Moving on to the brain. If an aneurysm ruptures
in the brain, blood will pool into the subarachnoid space putting pressure on the brain tissue
and irritating the meninges, causing symptoms like a very sudden and intense headache, and
the inability for someone to flex their neck forward. Another point on the list of terrible things
aneurysms can cause is blood clots. As blood flows past the aneurysm, some of the blood
might pull over into the extra lumen space caused by the aneurysm itself. This blood
isn’t being pushed along the blood vessel as quickly as the rest of the blood, and when
blood stays still for too long, it likes to clot. Given enough time the blood clot might
become so big it blocks off the entire blood vessel, causing tissue ischemia, or it could
break into smaller pieces called emboli and get wedged in a smaller blood vessel, also
causing ischemia. As an aside, it’s kinda of nifty that the
clotting property of blood is really useful to stop blood from leaking out of our blood
vessels, but it just also happens to be really really deadly if it stops the blood from moving
altogether. Honestly blood coagulation could be the plot for the third installment of the
Speed movies. Ok, back on track, abdominal aortic aneurysms
sometimes have signs and symptoms, and sometimes they don’t, even if the aneurysm has ruptured.
Really severe pain in the left flank which includes the abdomen, chest, lower back, as
well as the groin, a pulsating mass that is in time with the heartbeat somewhere in this
painful region, and hypotension occur in about 50% of aneurysms that have ruptured and are
considered the classical sign of an abdominal aortic aneurysm. Thoracic aorta aneurysms
usually don’t have any symptoms, although sometimes they can cause severe chest, back,
and abdominal pain. And there you go, that’s aneurysms. Aneurysms can be asymptomatic, and are sometimes
diagnosed incidentally when an individual gets an imaging study for another reason.
Usually they’re seen best on an ultrasound, CT scan, or MRI. If an aneurysm is present
and large enough to cause risk to an individual, it can be treated surgically. All right, as a quick recap… Aneurysms are
blood-filled bulges that form in weakened areas of the blood vessel walls. Left untreated,
aneurysms can burst, causing uncontrolled internal bleeding or excessive blood clotting.
Based on the size and location of an aneurysm, surgical treatment may be necessary.

10 thoughts on “Aneurysms – causes, symptoms, diagnosis, treatment, pathology

  1. Some fanfic author needs to crossover Speed with Osmosis Jones for that blood clot themed plot idea.

    Thanks for all the info!

  2. Every medical student en specialist should know atleast the basics of aneurysms! And this videos covers exactly that. Amazing 👍

  3. To add to the causes of aneurysms, there are connective tissue disorders that cause tissue fragility including vessels. I have Vascular Type Ehlers Danlos Syndrome, which is at a high risk of these developing, also Marfans syndrome is known for these too.

Leave comment

Your email address will not be published. Required fields are marked with *.