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Welcome to the Mastery course

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on salivary gland imaging.

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Some of you may have heard my 1-hour noon conference

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on salivary gland imaging, but we are going

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into a lot more depth today and show a lot

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more cases of salivary gland pathology.

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So that way, you're much more comfortable

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with salivary gland imaging.

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I have no disclosures other than the fact that I am a

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speaker for MRI online and one of the board members.

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So we're going to be talking about the

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anatomy of the salivary glands,

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the various scan sequences that we use in MRI for

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salivary gland imaging, as well as with CT.

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And then we'll separate into the neoplastic

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lesions and then the inflammatory lesions.

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Saliva is very important for those patients

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who undergo, for example,

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radiation therapy and develop

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xerostomia or dry mouth.

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That becomes a real problem with regard to oral

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hygiene, as well as the comfort

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that you have in your mouth.

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So we do produce about one to two liters of saliva a

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day, and it is predominantly created by the parotid

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gland, followed by the submandibular gland. And the sublingual

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glands and the minor salivary glands have a

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small contribution to the overall

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production of saliva each day.

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When we think of the major salivary glands,

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we're referring to the parotid gland,

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the submandibular gland, and the sublingual gland.

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Obviously, the minor salivary glands

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are scattered throughout.

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Let's talk initially about the parotid gland.

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This is a gland that has predominantly serous fluid.

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By that, I mean that it's relatively thin,

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it's not very viscous.

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The parotid gland weighs about 25 grams

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and has arterial supply,

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as one would expect from the external carotid artery

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and drains via the retromandibular vein

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which courses through the gland, and it drains

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from the retromandibular vein into the external

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jugular vein. It has lymphatics that

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drain into the cervical chain.

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The innervation of the parotid gland is through

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the sympathetic nervous system, parasympathetic nervous

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systems, as well as through branches of the third

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division of the fifth cranial nerve and the seventh

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cranial nerve: the greater superficial petrosal nerve.

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You may recall that the greater superficial petrosal

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nerve comes off of the geniculate ganglion in the

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temporal bone and courses anteriorly to predominantly

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provide salivation and lacrimation.

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So here are couple of diagrams and

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figures of the parotid gland.

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And on the sagittal view, you

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can see the parotid tissue.

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It goes down basically to the angle of the mandible,

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and the portion down at the angle of the mandible

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is what we call the tail of the parotid gland.

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As you can see, you have branches

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of the external jugular vein,

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retromandibular vein, and arteries from

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the external carotid artery.

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And then you have the duct leading from the gland and

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moving anteriorly to pierce the buccinator muscle

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at the second molar region.

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On our axial view,

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you see the parotid tissue and the predominant

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role of the retromandibular vein.

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And here we have portions of the parapharyngeal space.

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Now, the parotid gland has superficial and deep portions.

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Sometimes people will refer to them

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as the lobes of the parotid gland,

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but there really isn't a separate fascia that

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separates the superficial from the deep

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portion of the parotid gland.

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It also has parotid tissue that courses along the

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masseter muscle, one of the muscles of mastication,

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and also minimal parotid tissue that

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courses all along the duct.

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The duct of the parotid gland is called Stensen's

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duct, and it courses anteriorly to pierce at the

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second molar region of the maxillary molars.

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As I mentioned, the tail of the parotid gland,

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we use that term for that portion

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which is the inferior portion near

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the angle of the mandible,

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and the entire parotid space is encapsulated

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by portions of the deep cervical fascia.

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Okay, so here is our superficial portion

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of the parotid gland.

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And you see that there is the retromandibular vein

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which sort of marks the plane between the superficial

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portion and the deep portion of the parotid gland.

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We actually don't use the retromandibular vein.

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We should be using the facial nerve

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which is the true demarcation of the separation

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of the two portions. As you can see,

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it closely opposes the retromandibular vein,

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and that's why we tend to use that term.

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Some people use the stylomandibular tunnel, and that is

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from the styloid process to the mandible as the plane

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that separates the superficial from the deep portion.

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As you can see,

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this is the masseter muscle, and there is that portion

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of the parotid tissue which courses

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over top of the masseter muscle.

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So here is our MRI diagram.

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And what this is showing

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is a nice example of the facial nerve.

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Now, normally it's difficult to identify the facial nerve

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as it courses through the parotid gland because we

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don't really have a high-resolution imaging

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that is able to show that.

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However, in cases of pathology involving the facial nerve,

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particularly when it's enlarged or enhancing,

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we can see the actual facial nerve coming out

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from the stylomandibular tunnel. So here is

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the stylomastoid foramen.

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And this is the egress of the facial nerve

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from the temporal bone. So remember,

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we have the descending portion of the facial nerve, and

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it exits the skull base at the stylomastoid foramen.

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And this is being demonstrated here,

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where we have just a little bit of the mastoid tip,

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seen as the dark signal intensity.

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If we follow this facial nerve,

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we see it comes out. And then in close proximity

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to the retromandibular vein, it runs into the

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more superficial portion of the parotid gland.

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So in this patient,

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this would be termed the superficial portion

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of the parotid gland.

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And this tissue here, deep to the facial nerve,

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would be the deep portion of the parotid gland.

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So the facial nerve is very important for parotid

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surgery and for all considerations regarding the

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parotid gland because the surgeons don't want to

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sacrifice the facial nerve when they're doing surgery

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for superficial lesions, and they want to try to

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protect the facial nerve when they're doing surgery

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for deep lesions. And if they don't,

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then the patient obviously wakes up from

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surgery with a facial nerve palsy.

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This is a diagram showing that facial nerve for you

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diagrammatically running from along the plane

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of the stylomandibular tunnel. Again,

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from the styloid process to the back of the ramus of

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the mandible is that stylomandibular tunnel, and that

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approximates the location of the facial nerve.

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In this case, we can actually see the facial nerve.

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And this is a reminder to you that there is parotid

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tissue overlying the mastoid muscle.

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So this is our mastoid muscle.

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This is our pterygoid muscle.

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Here's our mastoid and our pterygoid muscle.

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And you note that there is a mass here

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superficial to the masseter muscle.

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And this was a pleomorphic adenoma of the parotid gland.

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So normally we think of the parotid gland back here,

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but there is a portion of the parotid tissue

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which overlies the masseter muscle.

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We also see here the duct of the parotid gland

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piercing the buccinator muscle at the level

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of the second maxillary molar tooth.

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So Stensen's duct.

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And here's Stensen's duct on the other side.

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More superficially,

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you see a little slip of something here. That's

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actually the zygomaticus muscle. It's a muscle.

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So we look for the one that comes right to the second

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molar region as the Stensen's duct and the one more

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superficial being the zygomaticus muscle.