Neuro: 2:00 - 3:00 Scribe: Kosha Shah and Susan Whitt

Neuro: 2:00 - 3:00 Scribe: Kosha Shah and Susan Whitt

Wednesday, January 13, 2010 Proof: Rylee Burt

Dr. Nicholas Cerebral Circulation and Disease Page 1 of 10

I.  Cerebral Circulation and Disease [S1]:

a.  Today’s next hour is going to be about the diseases that are associated with cerebral circulation

b.  Primarily we are going to be talking about strokes and bleeds

II.  Patient may awaken [S2]

a.  Patient is found down, paralyzed on one side of the body. And maybe a little out of it as their level of consciousness is concerned.

b.  It is the physician’s job to try to figure out the pathological passage and if there is something we can do about it.

III.  Image [S3]

a.  Most strokes—the name seems to mean when people are struck down. That is where the name comes from.

b.  This is a classic description of a person with stroke. Even though this is the classic description, it is not the only description.

c.  Most times, when you think about a stroke, a person is paralyzed on one side of their body or weak on one side of their body. They also have a sensory loss on the side that they are weak.

d.  These are usually situations where a clot forms somewhere in the arterial system and flies to the brain and blocks an artery, the main artery being middle cerebral artery. That’s what winds up with the patient looking like this.

e.  As you know, one side of the brain controls the opposite side of the body.

f.  If you were to have a stroke on the right side of brain, obviously the person’s weakness and sensory deficit would be on left side of brain and vice versa.

g.  As far as the face and head is concerned, the face and head is a little bit different from what happens in the body. Certainly the deficit is the same thing as the body deficit would be.

h.  One interesting thing about the deficits above foramen magnum is that the weakness of the face only includes the lower two-thirds of the face. So the forehead is spared.

i.  I realize that might be counterintuitive, but the facial nerve that is designed in that the top part of the nerve gets bilateral innervations: So you can have one side is completely out, but part of that nucleus on that spare side is getting bilateral forehead muscles.

j.  If the person is paralyzed on the right side, right arm and leg, their lower part of their face will be weak, but their forehead would be spared. That is what we typically see.

k.  As you may also see, there is an idea called dominance. Dominance means a number of different things, but for the most part we think dominance as being associated with language areas. The language areas are found on one side of brain and not other.

l.  Many times, there is correlation with their handedness as far as their writing is concerned. 99.99% of people who are right handed would be left-hemisphere dominant for language. However, about 80% of lefties are left hemisphere dominant for language. So it’s only a small percentage of lefties have a more balanced brain or right-sided dominant brain for language.

m.  These emboli that go to middle cerebral artery and infarct the surface of the cortex. If that happens on dominant side, you would get a language problem, and that is known as aphasia.

IV.  Critical Questions [S4]

a.  Some of the critical answers we have to answer when dealing with stroke.

b.  Is this a thrombo-embolic process or process within the blood vessel itself, a process we called ischemia in-situ?

c.  If it is a thrombo-embolus (thrombus is clot that forms and embolus is when that clot flies to another place), is this a problem with the anterior circulation or posterior circulation? What do I mean by that?

d.  The brain has two arterial supplies, which are known as the anterior and posterior circulation. The internal carotids will go to the brain—that is anterior circulation. You get another circulation through the back of the brain, the foramen magnum in the back of the your skull, which is through the vertebral vessels. As a result, you get an arterial supply from both places.

e.  Where is the thrombo-embolus going? Is it going up the anterior circulation or posterior circulation? And where did they originate?

f.  One spot that can generate thrombo-embuli that go into either circulation is the heart. We are talking specifically more about the left side of the heart, where the arterial blood is. That could go to the entire body, especially the brain when we are talking about a stroke.

g.  But there are also large spots where large arteries bifurcate. These areas, for some reason, there could be a potential for the inside of vessels to collect grunge. As a result, blood can slow down in those areas and you can have a thromboses forming there as well.

h.  Ischemia in-situ is a different matter in that this disease process in certain caliber blood vessels, penetrating vessels in the brain. They are associated primarily with two common diseases: diabetes and hypertension. In diabetes, we think that it is accelerated arterial sclerosis is the disease process while in hypertension, we think it is vascular wall hypertrophy that cause these blood vessels to choke off.

V.  Image [S5]

a.  When a person has a thrombo-embolus as we see in a typical case that winds up in the middle cerebral artery, this is what you see.

b.  You see a wedge shape in the ischemia. And they vary depending on the person.

c.  Most of these, but not all, the wedge goes all the way out to the cortex. When that happens, we are primarily talking about the pre and post central gyrus, which is the main motor and sensory strip in controlling motor and sensation from the opposite body.

d.  That is why the person ends up like you saw previously.

VI.  Arteries of Brain [S6]

a.  – This is the blood vessel we are talking about—the middle cerebral artery, which is found in the Sylvian fissure, which is this big crack that separates the temporal lobe from the rest of the body.

b.  It supplies the lateral aspect of the brain, so it is the most important blood vessel in the body.

c.  There are certain parts of the cortex that are related to certain parts body parts. They figured this out by doing surgery on people with them being awake.

VII.  HAL [S7]

a.  They would poke at a certain part of the brain and a certain part of the body would move.

b.  That is how they figured out that you could draw a little main on the surface of the cortex. The little man is known as a homunculus. This picture is a homunculus.

c.  As you can see, this is a coronal section, so you are looking at one side from the Sylvian fissure to the midline.

d.  You can see that most near the Sylvian fissure is the language areas-tongue, swallowing, those types of things.

e.  There is a large area that represents the face. There is a larger area that represents the hand. And then the trunk, and your butt is on top. And your legs and feet dangle between hemispheres.

f.  There are particular spots on the cortex that are related to specific body parts on the opposite side of the body.

VIII. Image S8]

a.  The Middle cerebral artery, again, is the main one we are talking about when see people with strokes.

b.  You can see this gray area, looking at the lateral aspect or medial aspect of brain, represents the area that is supplied by the middle cerebral artery.

c.  There are two other cerebral arteries as well. The one that goes down the midline, around the top like a Mohawk, are the two anterior cerebral arteries. And the one goes primarily to the back of the brain, including the occipital lobe, which is the site of the brain that is supplied by the posterior cerebral artery.

d.  What I kind of tell students, if they want to know the anatomy of the vasculature of brain, they should be able to draw the drawing that I am about to draw on the board.

e.  We refer to this as Willy or Willly the Spider because he kind of looks likes like a spider. We call him Willy for the Circle of Willis, which is the anatomical structure that makes up his face and surrounds the pituitary gland, which is the master gland of your brain.

f.  If we are looking at ventral aspects of the brain (took brain out and looked at bottom surface), we would see two cut ends of two blood vessels, which are your internal carotid arteries. These are the ICAs and they represent the anterior circulation.

g.  Lets keep a tally here: Cerebral arterie-1 2 3. Cerebellar arteries 1,2,3. Communicating arteries 1,2

h.  Coming out of the internal carotid artery and heading in between the two hemispheres like the antennas on an insect, this blood vessel will go down the midline as shown in the purple. That is the anterior cerebral artery.

i.  The big artery-The most important artery that comes out laterally on both sides out of the anterior circulation coming off the internal carotid is represented by the gray area. That is the middle cerebral artery.

j.  Wouldn’t it be nice if the anterior circulation take care of all of this and the posterior circulation take care all of this? But no, that is not how it works. Actually, you are looking at anterior circulation right there. That is kind of where it ends.

k.  Posterior circulation starts at foramen magnum with the two vertebral arteries. It makes an upside down V—maybe that can help you remember vertebral. They will come into form a blood vessel that sits at the base of the pons, which is called basilar. Many times anatomical names will make sense.

l.  The basilar will come up to a point where it will bifurcate and form two blood vessels that go posteriorly. What is next on our list? We have anterior, middle.

m.  Posterior is next. Since it is cerebral, that is what these are- the PCA. They are going to represent the yellowish green area of the cortex.

n.  Very near where the PCA comes off, there is another blood vessel that mirrors it. In between this vessel and PCA, there is a landmark, which is the third cranial nerve. If you see the third cranial nerve, this is the landmark that you may want to try to find. With the third cranial nerve, you should see two blood vessels go behind it, which are the PCAs, and two blood vessels that will go in front of it, and that would be the first cerebellar vessels that we come next to.

o.  Would it be nice if these names of these three vessels mirrored these names? But they don’t.

p.  The first one is called the superior cerebellar artery. Now we have two more to go. What is the opposite of superior? Inferior. But we have two to go. So how are going to do this? Well, they are both inferior. One is anterior inferior and the other is posterior inferior. The anterior inferior cerebellar artery is also known as AICA, and the posterior inferior cerebellar artery is known as PICA.

q.  AICA comes off “like about here”. PICA comes off the vertebrae. Not all of the cerebellar arteries come off the basilar. The PICAs come off the vertebral.

r.  In the picture, this is where the face is cause internal carotid arteries are like the eyes of the insect. It makes the circle of willis, but we don’t see the full circle yet.

s.  Don’t see a face yet-The pituitaries sit right “here” In order to finish the circle, we do so with vessels called communicating vessels.

t.  We have anterior and posterior vessels. Anterior, or ACOM, connects the two anterior cerebrals while PCOM comes off the posterior cerebral artery, and now we have Circle of Willis. That kind of looks like an insect. You should be able to draw this picture.

u.  Now what happens is when blood comes up the vertebral system, the posterior circulation, if there was an embolus there, it could lodge in any one of these blood vessels. While blood that comes up the internal carotid artery usually will lodge in MCA but can go up to the ACA.

v.  The communicating vessels—there is not much blood that is communicating there. But if you have an embolus going into the anterior circulation, you usually don’t see it actually going through PCOM to go into post circulation-usually don’t see that.

w.  Even though there is a connection there, many times you don’t see embuli taking advantage of that connection.

IX.  Image [S9]

a.  This is a very nice picture because it has all of these in here, but shows you how its related to the brain structures. Here is your post circulation, the two vertebrals. They come together to form the basilar, which on the surface basilar surface of the pons. Here is the PICA coming off the vertebral, AICA coming out, and then the superior cerebellar artery and posterior cerebral artery.

b.  Coming up the anterior circulation, the interior carotid, which does a little loop to loop before it gets into the skull and into the brain, one of the vessels (important vessel) is one that is not in his picture. It is the very first one, the ophthalmic artery. It comes off the anterior circulation and provides arterial blood to the eye. And then we get into our picture here. We have ACA and MCA.

X.  Clinical Signs of Carotid Artery Ischemia[S10]

a.  Many of you will have special interest in that first vessel, which is the ophthalmic artery. If you have a thrombus embolus, many times that thrombus embolus continues on to the MCA.