Interactive Transcript
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My name is Suresh Mukherjee and I'm a clinical
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professor of radiology at the University
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of Illinois at Radiation Oncology at the
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Robert Wood Johnson School of Medicine.
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I'm also a faculty member of otolaryngology head and
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neck surgery at Michigan State University.
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I also serve as national director for head
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and neck radiology at ProScan Imaging.
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This talk will be on the brachial plexus.
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The brachial plexus is something that we covered
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in medical school for a fair amount of time, but
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unfortunately, many of us forgot that anatomy.
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And it can be complex, but if you are
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a radiologist, eventually you will
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have to deal with the brachial plexus,
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whether you're a neuroradiologist looking
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down at the base of the neck, or whether
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you're a musculoskeletal radiologist.
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Because the shoulders are
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innervated by the brachial plexus.
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And even chest radiologists, because oftentimes
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you'll have pathology extending into the lung
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apices that can involve the brachial plexus.
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So therefore, you really can't escape it.
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So what we're going to do is discuss the
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classical anatomy of the brachial plexus.
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And then we'll show you how you can
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look at this on your imaging studies.
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So the classical anatomy of the brachial
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plexus that we learned in medical
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school is that it's divided into the
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roots, the trunks, the divisions, and cords.
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And sometimes, this type of
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anatomy is hard to remember.
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So, for me, I always like mnemonics.
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So, if I can always remember that
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radiology techs drink cold beer, and you
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can change beer to beverages if you like,
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but if you could remember the radiology
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techs drink cold beer, you could say,
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you'll always be able to understand
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the components of the brachial plexus.
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So when we break down the brachial
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plexus, the brachial plexus is supplied
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by C5 through the T1 nerve roots.
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And the C5 and the C6 roots
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combine to form the upper trunk.
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The C7 nerve root is by itself
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and forms the middle trunk.
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And then C8 and T1 combine
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to form the lower trunk.
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So in this schematic illustration, here's
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C5 and C6, and it forms the upper trunk.
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This is C7, which forms the middle trunk.
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And then you have C8 and
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T1 forming the lower trunk.
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Then eventually what happens is
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that these trunks end up dividing.
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So these trunks end up dividing and
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then the divisions eventually go on to
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form the cords of the brachial plexus.
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So the cords of the brachial plexus
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are named based on their relationship
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with the axillary or subclavian artery.
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So this red rectangle is here to identify and
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illustrate the axillary/subclavian vein.
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You have one cord
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that's posterior to the vein.
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You have another cord
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that's lateral to the vein.
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And then you have another cord
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that's medial to the vein.
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So again, the cords are named in relationship
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to the axillary/subclavian artery.
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So that's the classical anatomy of the brachial
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plexus that we learned about in medical school.
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So again, just to reiterate,
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C5, C6, C7, C8, and T1.
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We talked about the trunks,
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then we talked about the divisions,
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and then we talked about the cords.
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Now, the surgeons have their own definition
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of the brachial plexus, and that's based
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on the relationship to the clavicle.
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So on this schematic illustration, we can see
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the clavicle here, and the surgeons look at
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the brachial plexus as a component that's above
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the level of the clavicle, then you have a
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component that's behind the clavicle, and then
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you have a component that's below the clavicle.
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So this is the supraclavicular plexus,
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which is comprised of the roots,
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some of the nerves, and the trunks.
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The retroclavicular portion of the brachial
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plexus includes the divisions, and then the
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infraclavicular portion is predominantly
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comprised of the cords and the distal nerves.
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So you can see how the surgical anatomy
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has to take into account the standard
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anatomy that we learned back in medical
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school, the classical anatomy, if you will.
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So to put it all together, the
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third type of anatomy that I refer
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to is the radiological anatomy.
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And the radiological anatomy is as follows:
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In order to really understand the
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brachial plexus, there are three main
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components and three main anatomical
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areas that you have to be aware of.
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And if you can remember these three
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main anatomical areas, the brachial plexus
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actually will literally jump out at you
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on any type of study that you look at.
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So, the supraclavicular plexus that we
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talked about, and that's a nomenclature
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that the surgeons use, is comprised of the
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anterior and the middle scalene muscles.
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So, if you look at this schematic illustration,
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this is the anterior scalene muscle, this is the
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middle scalene muscle, and between these muscles
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comprises the supraclavicular brachial plexus.
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So, when we look at this anatomic image on the
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left, there's a lot of stuff going on right
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here, because we can see the thyroid
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gland, we can see the trachea, we can see the
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esophagus, we can see the vertebral body, we
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can see the paraspinal muscles, we can see
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arteries and veins, so it's relatively complex.
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But what I want you to be able to do is
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identify this muscle right here, which
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is the anterior scalene, and this muscle
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posterior to this with the middle scalene,
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and then if you look between the plane of
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the anterior and the middle scalene muscles,
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there's the brachial plexus.
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If you look at the opposite side,
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there's the anterior scalene, there's
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the middle scalene, and there's the
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brachial plexus right between them.
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So when you look at the brachial plexus,
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there's a lot going on, but these
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muscles, the anterior and middle scalene
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are pretty big muscles, and if you can find
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those, the brachial plexus is located within them.
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On the right-hand side is
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an axial T1-weighted image.
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And right here, we can see
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the anterior scalene muscle.
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There's the middle scalene muscle
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and there's the brachial plexus.
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Notice how it jumps right out at you.
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That's the supraclavicular
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component of the brachial plexus.
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On the patient's left-hand side, there's
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the anterior scalene, there's the middle
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scalene, and right between these are
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the supraclavicular brachial plexus.
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Now, this image on the right-hand side is
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really taken from a cervical spine MRI.
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And depending on how you do your cervical
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spine MRIs, whether or not you use a pre
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saturation pulse, if you don't use it, what
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I would encourage you to do is, yes, go
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ahead and look at all the pathology that's
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involved in the cervical spine, but over
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the next 20 cases, literally just look at
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the anterior and middle scalene muscles,
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and you'll see that brachial plexus.
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And once you do that, that supraclavicular
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portion of the brachial plexus will
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be very, very easy for you to see.
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That second component of the brachial
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plexus is comprised of the retro-
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and the infraclavicular plexus.
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And we can always find this by looking
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for the third main piece of anatomy,
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that we have to be familiar with:
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And that's the axillary
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slash subclavian artery.
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So, when we look at the anterior scalene muscle
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here, this artery that's medial to the anterior
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scalene muscle is the subclavian artery, and
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as it extends laterally to the anterior scalene
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muscle, it changes names to the axillary artery.
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And we can see on this schematic illustration
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that the cords of the brachial plexus are
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directly adjacent to the subclavian artery.
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In fact, when we talked about how these
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cords are named, they're specifically named
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based on the relationship to this artery, and
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once it gets lateral to the anterior scalene
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muscle, it's called the axillary artery.
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So when we look at the coronal images
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on this anatomic section, the arrow is
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pointing right here at the subclavian
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artery, and then just above it, we can
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see the cords of the brachial plexus.
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Similarly, on the left-hand side,
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here's that subclavian artery.
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As it extends laterally, it changes
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the name to the axillary artery.
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And right above it, we can see
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the cords of the brachial plexus.
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Laying right on top of it on the right-hand
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side is a fat-suppressed T2-weighted image. The
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arrow points at the subclavian artery, and right
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above it, lo and behold, we can see the cords
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of the brachial plexus. In fact, it looks just
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like spaghetti or some type of linguine
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that is literally laying on the subclavian
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artery on the left-hand side. Again, there's
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that subclavian artery, and right above it are
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the cords of the brachial plexus. So we can
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use this now to look at the brachial plexus
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on the sagittal images. The sagittal images
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were the way I initially learned to look at the
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brachial plexus, and quite frankly, I thought
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it was a little bit confusing, so I always
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default to the axial and the coronal images.
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But if you do look at the sagittal images,
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this is the anterior scalene muscle here.
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Here is the subclavian artery located
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just posteriorly to the anterior scalene
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muscle, and just adjacent to this
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are the cords of the brachial plexus.
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So, in summary, what we covered was
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the anatomy of the brachial plexus
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and how to find the brachial plexus.
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So as we begin this mastery course, it's
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important to understand that what you
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always have to look for are the anterior
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scalene muscle and the middle scalene muscle,
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because this identifies the supraclavicular
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portion of the brachial plexus.
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The third component is the subclavian artery.
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The subclavian artery is a big structure,
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and once you find that subclavian
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artery, you'll always be able to find
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the cords of the brachial plexus.
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And then, as the mastery course progresses,
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we're going to talk about a variety
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of entities that can cause brachial
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plexopathies, which include things like
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trauma, neoplasms, and inflammatory processes.
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And as we do this, we'll always revert back to
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the anatomic localizer, the brachial plexus.
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And hopefully, by the end of this course,
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you'll learn to love the brachial plexus.
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