 All right. Hello and welcome to the 10th of many live stream noon conferences hosted by MRI online in response to the changes happening around the world right now in the shutting down of in person events. We have decided to provide free daily noon conferences to all radiologists worldwide. Today we are joined by Dr. Rush McCurgy. He is a recognized authority and head and neck and neuro radiology. He has authored over 400 scientific manuscripts and book chapters and written or edited 12 textbooks. He is a consulting editor to both neuro imaging clinics and magnetic resonance clinics of North America. He is a devoted educator and has been invited speaker on over 400 occasions reminder that there will be time at the end of this hour Q&A session. Please use the Q&A feature to ask your questions and we will get to as many as we can before our time is up. That being said, thank you so much for joining us today. Dr. McCurgy, I will let you take it from here. Great. Thank you very much. Again, thank you for everyone that have joined this. You know, first of all, I want to thank MR online for putting this together. It's unusual times we're going through right now. And first of all, after I say thank you, I also want to hope everyone is safe and healthy times that I was born in the last century I trained in the last century but I've never seen any times like this and it became a little bit closer to home one of my colleagues mother who was very healthy yesterday. All of a sudden came down with COVID and is now on the brink of renal failure besides arts and is on a respirator so this is a real disease and fortunately and with that again I applaud MR online for providing really a global community service. I think there are people from all over the world. I've already got some nice WhatsApps and WeChat's from my colleagues around the world so you know in this time we're supposed to be alone but it's also nice to be alone together and I think this type of forum helps us communicate with each other and work with each other to realize that we're all sort of facing the same crisis but you know we will get through it together as well. Two other things, requests. If you can just send like an email maybe it'll be fun from a, I think on your ability to put a little chat box in is just say where you're from and just share it from all over the world. I've always been amazed at the power of the internet and so I know I would love to see where you're from I think we're already up to I think 764 participants and so I'd love to see where you're from. And also if you are watching it with more than one person just to see how many people are actually in groups together and how many people are actually touching so if you could embellish me with that I would certainly appreciate it. So what we'll do in the next 45 minutes or so is talk about the spaces of the head and neck and despite what many of the residents may think the spaces of the head and neck were not created just to torture you on your training exams. I know that's a common myth but it's not but in fact the spaces of the head and neck have been around for over 230 years someone say even longer than that. And the space of the head and neck were first described by these incredible French anatomists. And so what we're going to do is that we're going to go over the spaces of the head and neck. Now I'm a head and neck radiologist and you know I'm not the smartest person in the world I'm sort of like a Fred Flintstone radiologist so I'm not going to talk a lot about CTology or or MRI or petology or anything like that. One premise if if that I've always adhered to in the last you know 50 60 70 years that I've been doing this is the purpose of imaging is to show the anatomy and the best way to look if you understand the anatomy you can understand head and neck radiology. If you start adjusting your protocols to some of these newer sequences and then newer techniques and that prevents you from seeing the anatomy. Well sometimes it is one step forward and two steps back but really the key to this is to really it's all about anatomy. So what I'm going to do is talk about the various spaces of the head and neck and I've listed them there and hopefully make it a little bit easier because for me head and neck is super exciting. You know we have a worldwide audience and I want all of you to become head and neck radiologists that's my ultimate goal. But what I hope to do at the end this lecture is at the very least demystify it and make it a little bit easier for you so you're not going to be scared of looking at the various spaces of the head and neck and the first space that we'll talk about is the massacred space. Now I don't know about where you went to medical school where I went to medical school we did have a gross anatomy class and you know we would spend like two months on the liver and two months on the leg and you know two months on the you know fill in the blank but when it came to the head and neck we barely spent maybe two weeks on the head and neck and then all of a sudden as radiologists and we see something in the neck we have this daunting task about trying to not only understand the normal but also understand the abnormal. So what I'm going to first start about is the masticator space and pure and simply the masticator space and the muscles of mastication. So in order to understand the masticator space we have to see that this muscle right here that I'm contouring is the masseter muscle. This muscle here is actually the medial pterogoid muscle not the superior not the lateral but the medial. Here's a temporalis muscle and here is the lateral pterogoid muscle. So the most the largest component of the masticator space is the muscles of mastication. The next component that I'm going to contour and it's a little hard to see is there's a little oval shaped structure right here that drops down below for Amino Valley and that's the third division of the fifth cranial nerve. And the last component of the masticator space is the bone. So if I had to contour the masticator space on the right hand side this would be my contour which would include the muscles it would include the bones and it would include this little oval shaped structure here which is the third division of the fifth cranial nerve. So the components of the masticator space are muscle, bone and nerve with the largest component being the muscle. And on the coronal images if I had to contour the masticator space it would come down like here come all the way up and all the way up there. So if we just looked at a patient that had a mass involved in the masticator space and knowing that the muscle is the largest component if I was to tell you that there was a 14 year old boy that had a mass in the masticator space the most likely diagnosis is what it's probably going to be a rabdo myosarcoma why because muscle is the most largest component of the masticator space and the most common soft tissue sarcoma in a child is going to be a rabdo myosarcoma. So just realize that the anatomically based differential diagnosis of a masticator space mass is very easily going to be a muscle it's going to be a bone and then it's going to be a nerve. Now if you take that same approach and you move away from the head and neck. And so let's say you go to an accessory organ like the leg right. I know I have a lot of colleagues that are musculoskeletal radiologists but for me it's all an accessory organ to the neck. But let's just say someone asked you to give a differential diagnosis of a mass involved in the thigh. Well very easily, you can pivot to a differential diagnosis involved in the muscle so you can talk about lyoma lyoma lyoma sarcoma and so on and so forth and you can also talk about the bones right so you can talk about metastases and myelomas and the various sarcomas that arise from the bone and then you can always talk about the nerves. So the nerves include things like schwannomas neurofibromas etc. So my point is is that it's the same type of tissue that's in the neck. But when it occurs in the neck or the spaces we tend to have palpitations and get nervous. All I'm asking you is that when you now look at the head and neck and especially in the masticator space you don't necessarily need to think the neck. But just step back and say well what are the differential diagnosis for lesions that involve the muscle, the bone and the nerve. And if you take that approach and you'll be able to come up with a pretty sophisticated diagnosis involved in the masticator space. So here's an example of the mass involved in the masticator space now how do I know it's in the masticator space. Well, normal or abnormal it's obviously abnormal and I draw a line down the middle. Now we can see the mass here on the left hand side but notice what it's doing to the paraphernalia space it's facing the paraphernalia space it's not involving it. And so if we see this that we know the mass is involved in the masticator space. So what's the most common component of the masticator space it's muscle. And the next thing you have to do is you have to ask the age so this is an elderly male like myself unfortunately. So the most likely diagnosed in this case was in fact a Lyoma sarcoma. Here's another patient here's another mass involved in the masticator space we can see it right here. But in this case this was a child and this was a 14 year old child that had a mass in the masticator space. The largest component the masticator space is muscle. This is involving the soft tissues. So this in fact was a rabdomyosarcoma. Here's another lesion these are these crazy jaw lesions that you always have to worry about but again, if you sometimes if you don't think head and neck and you think other areas you could easily make the diagnosis that this bony excrescence here is an osteoma. This person right here this lesion right here is one of those crazy jaw lesions, and this in fact is an ameloblastoma. So this is one of those head and neck lesions but again, you can come up with a relatively sophisticated diagnosis by remembering muscle bone, and then we always have to remember the nerve. So this was a patient that had a nasopharyngeal carcinoma. Here's the here's the lateral pterigoid muscle and we can see this mass right here. Remember v3 is just medial to the lateral pterigoid muscle. So because this muscle is displaced medially as is seen here and we see this rounded lesion, then we know that this is arising from the nerve and this happens to be perineural spread of tumor from nasopharyngeal carcinoma. And this lesion another lesion here again it's involved in the masticator space why because liquid it's doing to the lateral pterigoid muscle it's displacing it laterally. And when we look at the coronal images we can see this mass extending superiorly through Framono Valley. And again this was a schwannoma involving v3 extending into the Framono Valley. So when we talk about the masticator space. And again if you're taking notes this is what I would suggest writing down is muscle bone and nerve. And if you remember muscle bone and nerve for the masticator space, you'll be able to come up with a pretty sophisticated differential diagnosis. So the next space that we'll go on to is the visceral space. Now I don't like to memorize I'm a terrible memorizer so but here's one thing that you have to remember when we talk about the spaces of the head and neck. And that is the fascia of the head and neck now I would assume the majority of us. On this call are actually radiologists and maybe the reason we went into the radiology because we weren't good at dissecting. So if you did do your dissections you may remember hopefully coming across the fascia of the head and neck. Now this fascia right here which is the middle layer of the deep cervical fascia is referred to as the visceral fascia. Now this was the original name give it to it back in the 1930s. So this is the article by gradinsky and holy oak and I would strongly if you really like heading to go back and look at it, but they call this the visceral fascia. Now the thing about head and neck that again makes it difficult is that we can take the same piece of anatomy and different give it different names. So over time the visceral visceral fascia has acquired different names. Some people will call it the fringo mucosal fascia. At the top it transitions into the fringo basilar fascia, so on and so forth but I still use the term visceral fascia. So if I use the term visceral fascia what do I term the name of the space that's encompassed by the visceral fascia well pure and simply that's the visceral space. So how do you remember without memorizing what's in the visceral space. Well it's actually pretty easy. You know if you are with a group of people right now, or if you're by yourself and you're really bored take up a mirror and open your mouth and say ah, well if you do that. Everything that you can see in the mucosa of your mouth, everything you can see in your mouth or in your throat. That is the visceral space. The visceral space pure and simply is that space delineated by the visceral fascia and basically it's everything that you do when you look into your mouth. So that's how you can always remember the visceral space. So here's a patient right here that has a tumor that's involved in the visceral space. This is a nasal pharyngeal carcinoma. In the different part of the upper air digestive tract it could be a squamous cell carcinoma involving the oral cavity or the oral pharynx, so on and so forth but that's all in the visceral space. Now one thing to remember about the visceral space is that the majority of these imaging findings are non specific. So here's a mass involving the visceral space. This happened to turn out to be an adenocarcinoma. There's absolutely no way that you can make this diagnosis just based on imaging findings. But the important thing to remember is that the purpose of imaging, especially when you're looking at a mass involving the visceral space, is not to give a differential diagnosis of 10 things. Rather, the referring physicians can see this mass, they can biopsy and the pathologists can tell the diagnosis. Our job is to look for deep extent. So just remember when you're dealing with the visceral space mass, remember that the majority of physicians can see that lesion when they perform their agoscopy. Now this is a quote unquote visceral space mass in a child. We can see that there's a lot of increased soft tissue involved in the visceral space. But remember, in this particular case, this is just normal adenoidal hypertrophy. And how can we be sure of this? We can be sure of it is that when we look at these deeper structures, so here's a tensor vellipalatini, here's a levator vellipalatini, excuse me. Here's the tensor and here's the levator, apologies. And we can see there's no deep extension through the visceral fascia. So this is just benign adenoidal hypertrophy. And this is a lesion here, a submucosal lesion here below the visceral fascia. It's located in the pharyngeal bursa. It's high signal on T1 and this is the classic torn wall cyst. Again, this they may not be able to see on direct endoscopy because it is submucosal. And it's also quite a commonly incidentally found on endoscopy. Or excuse me, I should see on brain and Mars. So the next thing that we'll talk about is to talk a little bit about the next space and this is pure and simply what do you call the space that's located behind the pharynx. So the other name for the visceral faces is the pharynx because there's a nasal pharynx and oral pharynx and a hypo pharynx and pure and simply that space that's located behind the pharynx is referred to as the retro pharyngeal space. But if you look at the fascia that we talked about, there's one fascia right here, which I mentioned before, that's the visceral fascia. There's another fascia right here, which is the pre vertebral fascia, which we'll talk to. And there's another fascia layer right here, this dashed line, which is referred to as the alar fascia. So the true retro pharyngeal space is between the visceral space and the alar fascia. So this is the true retro pharyngeal space. The space that's located between the alar fascia and the pre vertebral fascia is referred to as the danger space. Look, I know we have a lot of things going on in our lives right now, and I know it's Friday, but on Saturday, if you can just remember that the space behind the pharynx is a retro pharyngeal space, I'm going to be very, very happy. But for the aficionados here, just realize that this space is subdivided by the alar fascia into a true retro pharyngeal space and the danger space. And this was just a pace that had trauma, and here we can see air in the retro pharyngeal space. This is another example of a lesion involving the retro pharyngeal space. Here we can see the carotid artery that wanders into the retro pharyngeal space. And this is, if you will, the wandering carotid artery. Now, when we look in the retro pharyngeal space, there's really not a lot of anatomy there. Basically, it's some fat, it's some fiber fatty tissue, but you do have these things in green right here. And these are the retro pharyngeal lymph nodes, and there's a medial and lateral group. So the normal retro pharyngeal lymph nodes here, there's a medial and lateral group of retro pharyngeal lymph nodes, and this is a metastatic lymph node involving the retro pharyngeal space. How do we know where it is? Because here's the carotid artery, and the retro pharyngeal lymph node is located right there. Now, this is a child that has sore throat and has swelling and is really worried about an infection. Now, this is not a true retro pharyngeal space abscess. What this is, is pus in the retro pharyngeal lymph nodes, and this is what we refer to as separative adenitis. Now, this is a true retro pharyngeal space abscess, and this abscess we can see crosses midline. Now, as I mentioned before, there's a retro pharyngeal space and a danger space, and these spaces extend inferiorly into the mediastinum. The inferior aspect of the retro pharyngeal space ends at approximately T2 to T6, and in this case we can see this retro pharyngeal space abscess extending into the mediastinum. So anytime you do see that fluid collection here involving the retro pharyngeal space, make sure you extend your imaging into the mediastinum because this is all continuous. The danger space, which is an orange, extends all the way through the mediastinum and extends into the crew of the diaphragm and is continuous with the retro peritoneum. So the bottom line is, is that that space that's located behind the pharynx is a retro pharyngeal space. So, so far we've covered the masticator space and one of the three things we want to remember muscle bone and nerve. Visceral space. Whoops, sorry about that. Visceral space. What do we remember about the visceral space? Open your mouth and say, ah, every time you can look in someone's mouth, you're actually in the visceral space. What's a retro pharyngeal space? Well, the retro pharyngeal space is really just that space behind the visceral space. Well, let's move now to the pre-vertebral space. Now, as mentioned before, there's this fascial layer right here, which is called the pre-vertebral fascia. That was the original name by Grodinski and a holy oak and also used by back in the days of Ruvier. But this has changed as well too. So now people now refer to this as the peri-vertebral space. So it depends again, we take the same piece of anatomy and give it different names. This one's really, really easy because every one of you that has looked at a spine MR, a cervical spine MR or a cervical spine CT has knows exactly what's in the pre-vertebral space. We don't call it the pre-vertebral space, but we call it the spine, right? But the bottom line is that you already know about this. So the most common pre-vertebral space masses are going to be what? Well, in this case, this is a retro pharyngeal space abscess that extended through C1, C2 and is causing a epidural abscess. This is a case of POTS disease here. Other causes of pre-vertebral space masses, well, and you can have discurneations, you can have osteophytes, you can have any type of degenerative causes of masses that are pre-vertebral space masses. Again, we don't think about it as a head neck space, but they are. Now, occasionally there are certain head and neck lesions that arise in the pre-vertebral space. So here's a patient that has a large aggressive mass that's involving the very top of the pre-vertebral space. If you will, it's at the top of the notochord. And on T2, it's high signal. So I think everyone knows what this diagnosis is. This is going to be a cordoma. And the reason why it's high signal on T2, but solid, it contains those famous fissiliferous cells or fissiliferous cells. Don't ask me to spell it, but that's what those are the cells that combine it. And this is just another example here of a patient that has a mass involving the pre-vertebral space. No way you can get this. It's a plexiform neurofibroma, but I show it to highlight the mass involving the skull base here. So this is involving the pre-vertebral space. And here's an example right here of a calcified lesion that's involving the pre-vertebral muscles. And this is an example of calcific tendonitis. So here's calcification of the longus coli muscles. The other term that I use for this is gout, if you will, involving the neck. And it's probably not the right thing to say, but that's the way to think of it. It's deposition of calcium hydroxyapatite. Another pre-vertebral space mass. This mass right here, patient with trauma, has a dissection involving the vertebral artery. Again, we don't think of this as a pre-vertebral space, but this is in our differential diagnosis of a pre-vertebral space mass. So when we think of the pre-vertebral space, we think of bone, we think of disc, we think of the vessels, and we think of some of those strange head-neck lesions that we always have to consider the cordoma. So the bottom line is, is any differential diagnosis that you have for spine lesion, you can immediately map that to the pre-vertebral space. So if you've looked at a spine M or a looked at a spine CT, believe me, you got this one. So the next one is really hard. See how hard the spaces of the head and neck are. If you really want to have something hard, go do mammography. I have no clue about mammography. On the other hand, what's the next space? Well, what do you call the space of the head and neck that contains the parotid gland? Well, that's exactly right. You call it the parotid space. So basically, it's very, very easy. The space that contains the parotid gland is the parotid space. Now, the parotid space contains a very important nerve, and this nerve right here, which is seen here, is the parotid space. I give credit. I think he may be on here. Martin Ferraro from Argentina. Martin gave me this beautiful case of morphologic institute. So Martin, if you're out there, thank you very much for letting me use this case. So the facial nerve right here separates the parotid gland into a superficial and deep lobe. Now, we can't always see the parotid gland, excuse me, the facial nerve, but we can have a pretty good approximation of where it's located. So there's a vein right here that's located behind the mandible. And what do we call this vein that's located behind the mandible? Well, that's called the retro mandibular vein. The facial nerve is located just lateral to the retro mandibular vein. And this facial nerve, as you can beautifully see here, and also in this diagram here, this is kind of interesting. This diagram is not something I created from PowerPoint, but this is from Charles Bell, the person that Bell's palsy was named after Charles Bell that he wrote in the 1800s. So this anatomy has been around for a long time. But the point of this is notice how the facial nerve provides this plane. So this plane separates the parotid gland into a superficial and a deep lobe. So when we think of the parotid gland, number one, the space that contains the parotid gland is the parotid space. The next thing we have to do is remember the facial nerve, and we can always find the facial nerve because it's just medial to the retro mandibular vein. And that separates the parotid gland into a superficial and a deep lobe. Those are the three main concepts when we talk about the parotid space. So what are some differential diagnosis involving parotid space masses? So here's a mass, a patient that has bilateral masses involving the parotid space. Now these masses are bilateral in this case, and sometimes these lesions can be multiple and to involve the same parotid gland. Now if the patient had no history of lymphoma or had no history of metastases, then the most likely diagnosis starts with a W, and that's the Wharton's tumors. Now why do Wharton's tumors arise in the parotid gland? Because the other name for Wharton's tumors is called cyst adenoma lymphomatosum. So basically the parotid glands contains multiple lymph nodes. They're located in the pretragal region below the capsule, around the facial nerve, and in the tail. And this lymphoid tissue is where Wharton's tumors arise from. So that's why Wharton's tumors can be bilateral and they can be midline. This was a page that has multiple cystic lesions involving the parotid gland. If I told you this patient was HIV positive, well this is the classic lymphoepithelial cyst that can involve the parotid gland. Now here's a patient that has this lesion that's involving the parotid gland. It's involving the deep lobe and extending deeply into the space that we'll soon talk about, which is a space next to the pharynx, and that's the parapharyngeal space. This lesion is solid, but also has high T2 signal. Now this is not a cordoma, but in a way these signal characteristics in a way mimic a cordoma, although they're histologically distinct, but this is a pleomorphic adenoma. So pleomorphic adenomas are solid lesions they enhance, but on T2 the classic appearance is its high signal. They can occasionally have heterogeneous signal as well too, but when you see this, it's a pleomorphic adenoma. And this is another pleomorphic adenoma here. So this one's just involving the superficial lobe, whereas this lesion is involving the deep lobe. So the key concepts here, parotid space mass, it's involving the deep lobe, it's extending into the parapharyngeal space, and this type of imaging appearance, you can make a pretty good diagnosis with a high degree of confidence that this is a pleomorphic adenoma. This is an example of the importance of understanding the facial nerve in the parotid gland. So this is a patient that has an adenoid cystic carcinoma, a aggressive malignancy involving the parotid gland. And remember, these tumors can jump along the facial nerve, and this is an example right here of retrograde perineural spread along the facial nerve involving the descending portion of the right facial nerve. So again, the importance of the parotid gland, what are those key pieces of anatomy? Again, you don't have to memorize everything. Just remember those key pieces of anatomy. So parotid gland is number one. What's the nerve? The facial nerve. How do we find the facial nerve? It's next to the retromandibular vein. The facial nerve divides the parotid gland into a superficial and a deep lobe. And remember, you can always have the potential for retrograde perineural spread. So if you just remember those four or five concepts about the parotid gland, that's going to allow you to evaluate and really understand how to better interpret lesions involving the parotid space. Well, the next space is really pretty easy. Again, all of this is pretty easy. Let's do a little review. So what do we call the space here that contains the masticator space? The muscles of mastication, that's the masticator space. What do we call the space here that you say, ah, you look into? That's the visceral space. What do we call the space behind the pharynx? Well, that is the retrofaryngeal space. What do we call the space that contains the spine? Very easy, right? The pre-vertebral space. And what do we call the space that contains the parotid gland? Well, that's just pure and simply the parotid space. Now I'm going to make it really hard now. Ready? What do you call the space that's next to the pharynx? Well, pure and simply, that's just the parapherangeal space. Head and neck really is that easy. And it's that easy if you understand the anatomy. So here's an example of a mass involving the parapherangeal space. So how do we know it's involving the parapherangeal space? Notice how the carotid artery is displaced posteriorly. And notice how the medial tear gourd is displaced anteriorly. This tells you that this is arising in a location that is pushing this muscle up, but is displaced in the carotid artery more posteriorly. So this is a mass involving that parapherangeal space. And this is a pleomorphic adenoma. The most common lesion to arise in the parapherangeal space to originate in the parapherangeal space is a pleomorphic adenoma. Now here's a mass that's involving the parapherangeal space. So if we look at the normal parapherangeal space on the right hand side, we can see the typical triangular fat pad here involving the parapherangeal space. But notice on the left hand side, the parapherangeal space is kind of squashed. It's compressed. And this is a tumor involving the tonsil that is extending into the parapherangeal space. So the most common lesion to extend into the parapherangeal space, the most common tumor to extend into the parapherangeal space is deep spread of a swamous cell carcinoma. So it's important to differentiate the most common tumor to arise in the parapherangeal space, which is pleomorphic adenoma from the most common tumor to extend into the parapherangeal space, which is deep spread of squamous cell carcinoma. All right. Hopefully everybody's with me so far. The next space, again, it's really, really easy. What do you call the space that contains the carotid artery? Well, that is pure and simply the carotid space. And again, it all boils down to anatomy. So when we talk about the carotid space, this was the term, again, that was used before with Grudinsky and Holyoke back in the 1930s. And I think the term has been able to weather the test of time. But there's another name for the carotid space. There's something called the carotid sheath. Again, if you're dealing with the ENT surgeons, the carotid space is also known as the post styloid parapherangeal space. Let me try to explain this anatomy to you. I mentioned earlier that the space next to the pharynx is called the parapherangeal space. And if we're radiologists, we call this space the carotid space. And if you're an ENT surgeon, sometimes they will refer to this space that we call the parapherangeal space as the pre-styloid parapherangeal space because it's anterior to the styloid process and the space posterior to the styloid process as the post-styloid parapherangeal space. So remember what I was telling you is that we take the same piece of anatomy and we give it different names. The nice thing now is I think there is a growing consensus that we will call this space the parapherangeal space and this space the carotid space. Now, what are the components of the carotid space? You know this already. You already know it. And that's the carotid artery, the jugular vein. You've got some nerves here, which are cranial nerves 9, 10, 11, and 12 in the upper part of it. You also have lymph nodes and then you have this lesion right here, which is a sympathetic chain. But the majority of pathology is going to be involving this. Now, just step back for a second. All of a sudden I can see everyone getting nervous. It's head and neck. I'm like, how am I going to memorize this? I'm going to tell you, don't worry about it. Just don't worry about it because any time that you have this normal anatomy of an artery, a vein, a nerve or a lymph nodes, anywhere in your body, you can take that same differential diagnosis and just map it directly into the head and neck. So let's see how this works because it's really not that bad. So everyone knows this big, large, enhancing dilated mass involved in the left carotid space. Well, this is an aneurysm. You get aneurysms everywhere. You get aneurysms in your chest. You can get it in your abdomen, get anywhere in your body. So you know that, right? But that's a carotid space mass. What if I told you this patient had a prior history of a central venous catheter? Well, this is jugular vein thrombosis. Why? There's a jugular vein. There's a carotid artery. There's a carotid artery. There's a jugular vein. Again, very, very simple stuff. Another example of a carotid space mass, this patient ended up having trauma. Here we can see a narrowed lumen and it's surrounded by this eccentric area of increased T1 signal. And that is just a dissection involving the left carotid artery. But now, another example here. Now, here's a mass and I'm going to trick you on this because I bet I know what everyone's going to say. Here's a mass that's involved in the carotid space. But be careful here, okay? This is intermediate signal on T1. And look at T2. It's very, very homogeneous. And when we do an MRA, we can see there's no flow at all. The diagnosis here is a schwannoma. And the key thing here is that if you see these masses involving the carotid space, and they're at least 2.5 centimeters in size, and you do not see flow voids, and that's a pretty accurate or definitive or confident way to say that these are not hypervascular lesions like a glomus tumor, but this, in fact, is a schwannoma involving the carotid space. This, on the other hand, is your classic case of a paraganglioma, or sorry about that, but let me go back there. Hold on. Don't look. There we go. Here's another example here of a patient that has a mass involving the carotid space. Now, how do we know it's in carotid space? Look at the carotid artery. It's being displaced anteriorly. If the carotid artery was being displaced posteriorly, then this would place it in the parapharyngeal space. So this is a hypervascular lesion arising in the carotid space, and this is a glomus tumor. And this is the coral of angiogram telling us that's what it is. Now, what types of glomus tumors arise in the head and neck? Well, there's actually four types. This glomus tumor is arising from the crotch of the internal and the external carotid artery. And notice how the external carotid arteries displaced laterally, and the internal carotid artery is displaced laterally. So this is a true carotid body tumor. If the internal and the carotid arteries were pushed together, then this would be a glomus vagalli tumor. If this lesion was arising right here at the skull base, in the jugular frame, and then that would be a glomus jugulari, and if this was arising in the middle ear cavity, then it would be a glomus tympanica. So remember, carotid body tumors displaced the internal and the external carotid arteries. The glomus vagalli tumors pushed them together. If it arises at the skull base, and that's a glomus jugulari, and if it arises in the middle ear cavity, it's a glomus tympanica. Well, the last couple of things that I'll talk about in the last two spaces, again, are very, very simple. Look what we've done so far. We've gone from massicator space to visceral space to rectifier and geospACE, to pre-vertebral space, to carotid space, para-ferring geospACE, carotid space. And I bet all of you can remember this. The next space, it's very simple. Again, very, very simple, but you have to learn a little bit about the classics. And you have to learn a little bit about the Greek and Latin roots of words. So the Greek root of tongue is glosses, and the Latin root of tongue is lingua. So when we talk about the next space, if we can remember that the sublingual space and lingua is Latin, then we'll remember that the sublingual space is that space that's below the tongue. So remember that friend you make, or in case you're bored, if you want to, very simple. How do we remember where the sublingual space is? Well, you just take your finger, and I'm going to demonstrate. Take your finger, work with me here, okay? Open your mouth, the guy of tongue. So that's now recorded. So if you ever forget where the sublingual space was, literally open your mouth, stick out your tongue, and then just go ahead and stick your finger below your tongue, and you'll always be able to figure out exactly where that sublingual space is. Now, what's the anatomy of the sublingual space? Well, the lateral margin of this is formed by the ramus of the mandible. The wall of the sublingual space is formed by the mylohyoid muscle, as is seen here, and then the floor of this is formed by the hyoid bone. So in this anatomic image again, there is the mandible. Here is the mylohyoid muscle. Here is the hyoid bone. And you can see on the opposite side, there's another mylohyoid muscle, and there's a mandible there. So the way I think of this, it's like a teacup. So basically, anytime that you can pour tea into a teacup, everything that's in that teacup is in the sublingual space. So for me, the rim of this is the mandible. This part here is a mylohyoid muscle, and the floor is the hyoid bone. So everything within that teacup is in the sublingual space. So here's a schematic illustration of a mass involving the floor of the mouth. Here we can see a tumor here. This is a classical example of a squamous cell carcinoma. Maybe one day later we can talk about imaging findings of squamous cell carcinomas of the oral cavity and the oral pharynx. We don't have time to do it today, but that's really in a lecture unto itself. But the most common tumor to involve the sublingual space is a squamous cell carcinoma of the floor of the mouth. Now here's an example of a tumor that's a lesion involving the sublingual space, and we can see this mass right here. We can see it's fluid. It could be a lot of things, but if I tell you the patient had a fever, you can go back and you can look at the bone right here. We can see that bone is very, very sclerotic. And if you have a really, really sharp eye, you can see this lesion right here around the tooth, this little leucency right here. And this is the rotten tooth. This is a little periapical abscess that has resulted in this chronic osteomyelitis that has now resulted in a floor-of-mouth abscess. Now, what about some of the cystic lesions that are involved in the floor of the mouth? Here we have an anterior midline cystic lesion. That's, again, an important thing. It's midline and it's involving the floor of the mouth. So this is an epidermal. Now, I'm going to break a little bit from here because I want to point out the name of this muscle. This muscle goes from the geniotubical to the tongue base. See the transverse fibers of the tongue base? And there is the muscle right here. Well, that muscle is the genioglossus muscle. So remember, sublingual is Latin for tongue. Glossus is Greek for tongue. So when we talk about the spaces, we use the Latin root and its sublingual space. When we talk about the muscles like the genioglossus muscle or the hyoglossus muscle, then then we use the Greek root. So that's where the confusion comes in. Now, sorry about my pointer here. It's, for some reason, it goes transversely. But you can see the cystic mass that's located right here. And that cystic mass is a pyramid line mass that is continuous in this particular case with this gland right here. And what do we call the gland in the sublingual space? That's right. It's pure and simply the sublingual gland. So this is a congenital obstruction and a little bit of a dilatation involving the sublingual gland. And we all know the name of this. You have to remember a frog. And if you remember the frog, you'll always be able to remember that this is a ranula involving the sublingual space. Another example of a ranula, ranulas can be bilateral, as is seen here. What muscle is this? It goes from the geniotupical to, you can see very nicely, the tongue base. So this is the genioglossus muscle. Here, we can see that the ranula right here is above the mylohyoid muscle. So this type of ranula that's located above the mylohyoid muscle that's contained in the sublingual space is referred to as a simple ranula. Now, if this ranula extended deeply through the mylohyoid muscle into the next space that we talk about, again, it's the same piece of anatomy. It has three different names. So the ranula that extends below the mylohyoid muscle, if it's not simple, it's complex. It can dive through the mylohyoid muscle or it can also plunge through the mylohyoid muscle. So complex diving or plunging, all of these names have been given to the ranula. And unfortunately, that's what makes head and neck hard. It makes it hard because we take the same piece of anatomy and we just give it different names. So apologies for that, but once you understand the concepts, it's pretty easy. And what's the last space? What's the last space that we're going to talk about? Well, the last space is that space that's below the mandible. And pure and simply, what do you call the space that's below the mandible? So here's our mandible here on this beautiful anatomic image. Here's our mylohyoid muscle here. Here's our mylohyoid muscle here. Everything above this is the sublingual space and everything below this is in the submandibular space. So pure and simply, the space that's located below the mandible is a submandibular space. Anyway, what's the name of the space up here? Easy, right? Even this muscle right here, this is all massicator space. There's your masseter muscle. There's your temporalis muscle. Here's your lateral pterogoid muscle. Here's, excuse me, here's your lateral pterogoid muscle and here's your medial pterogoid muscle. Again, it's all about anatomy. So the space below your mandible is a submandibular space. How will you always remember the submandibular space? Now, I think my wife was earlier on the call, but she signed off right now so I can say this and not get in trouble. So if you have a dog, a cat, or a spouse like this, I do this to my wife all the time. Actually, she'll hit me if I ever did this to her. But if you literally tick your chin, if you have a dog or a cat, don't they love to be petted like this under their chin? You should try to do that. If you're especially brave, do it to your spouse. You have a lot of time together. So, you know, why not make the best use of it? If you could do something like this, that is you've been palpating your dog, your cat, or spouse's submandibular space for the last, you know, how many years you've had that creature, right? So you can always remember the submandibular space. So what are the components of the submandibular space? Well, the most common component, the most numerous component are these lymph nodes. And these are the level one lymph nodes that are located in the submandibular space. And so, again, we don't have talk to get into the lymph nodes. Maybe one day I'll get invited back when we talk about head and neck lymph nodes. But these are all level one lymph nodes that are located in the submandibular space. Again, the most numerous component of the submandibular space. So here's an example. If you're in a busy private practice, this is one of the most common reasons you'll be doing head and neck imaging. Here we have dilatation of the left submandibular gland. We can see this lesion here. With a leap of faith here, we can see this dilatation of the duct. And the reason that duct is dilated is because of this little stone right here. So this is a Psyalibut involving the sublingual space, but because the duct of the submandibular gland runs in the sublingual space and enters at the phrenulum. This is causing an obstructive Psyladinitis involving the left submandibular gland. Another example here, this is dilatation of the left submandibular gland. It's not a lymph node. It's dilatation of the left submandibular gland. And if you draw a line down the middle here, we can see fat here on the right side, but very subtly notice how all that fat is gone on the left side. So this obstruction of the submandibular gland was due to a very, very subtle squamous cell carcinoma here that was causing an obstructive Psyladinitis. So it's a little bit of an older case, but again, makes a very, very important point. If you see obstruction of this gland, make sure you look for the stone, but very carefully scrutinize the fat in the sublingual space to see if there's a subtle little squamous cell carcinoma. And finally, the last case that we'll talk about is this. So I think we all know the diagnosis here. We have a pyramidaline cystic lesion involving the sublingual space. If we look in the submandibular space, we can see this ranula has now dived or plunged, however you want to say it, into the submandibular space. And really, if you look very closely, it has a little small little brother here on the left-hand side. So this is a plunging ranula that extended in the sublingual space into the submandibular space. The reason that's important is that if you, the radiologist say that the ranula is located in the sublingual space only, then the surgeons can marsupialize this through an intraoral approach. But if you, the radiologist say that this ranula has extended below the submandibular space, then the type of surgery that will need to be performed would have to be not only an intraoral but a cervical approach. So again, that's the real value added of radiology. So I think I'm on time. We'll have about 10 minutes for questions. But what I wanted to do is to again review and tell you away hopefully that you don't have to memorize anything. And just kind of take a holistic approach and just remember how we can remember some of these key concepts. So number one, the masticator space, it's the muscles of mastication. What are they? They're muscle, there's bone, and there's nerve. That will give you your masticator space mass differential diagnosis. What about the visceral space? The visceral space is open your mouth and say, ah, everything that you can see in the mouth is in the visceral space. The retrofaryngeal space is at space behind the pharynx. Very simply, the retrofaryngeal space. The pre-vertebral space is just the spine. The parotid space is what contains the parotid gland. The parapherangeal space is next to the pharynx. The carotid space just contains the carotid gland. The sublingual space, ah, below your tongue, and the submandibular space is right under your chin. So with that, I just want to thank all of you. I think we had up to 1200 attendees today. It's been a real pleasure. Thank you so much for taking time to attend. It means so much to me. And thank you for allowing me to, for us all, if you will, to be alone, but be together. Thank you very much for your attention. Thank you, Dr. McCurgy. Do you have a couple minutes for some Q&As? Sure. Perfect. Do you want to go ahead and open the Q&A section and answer the ones you see fit? Yeah, sure. Let me go into this. So here's one for you, Ashley. Someone emailed me and said, how can I access the larynx lecture that we gave last time? So can you answer that one for me? Yeah, I'll send them a message. Fantastic. Okay. Someone asked a question about how can you delineate the fascia on the CT? That's a great question. You really can't see the fascia in most instances. You just can't see it. So a lot of it is knowing where to expect to see the fascia. So you really can't see it, but that's why if you do know where the back of the pharynx is, if you do know where the back of the pharynx is, then you'll be able to identify the expected location of the visceral fascia. So if you know where the anterior margin of the spine is, you'll be able to delineate the anterior margin of the pre-vertebral space. So you really can't see it on CT, but it's good to know if you understand your anatomy, you should be able to approximate the location. Okay. Someone said here, what's the demarcation between the danger space and the perivertebral space? Again, they use the term perivertebral space, perivertebral space or pre-vertebral space. It's all the same. So the demarcation in the perivertebral space is going to be the pre-vertebral fascia. So the pre-vertebral fascia, so you have the danger space and behind it, you have the pre-vertebral fascia, and then behind that you have the pre-vertebral space. The next one is a normal cutoff of the pre-vertebral space at all cervical levels. I'm not sure what that means. Maybe it's the regular thickness. I would say it's about, if I remember back from my residency, I don't look at plane films that often. I would think it's maybe four or five millimeters, but I would have to defer to the pediatric textbooks for that. So how to locate the palentine tonsils easily? So I think I can answer that one. Let me see if I can close this up. And I can break from the script here, and I can show you very easily the palentine tonsils. Let me go back. So here's an example here. This was that case I showed of the wandering carotid artery. These guys right here are the palentine tonsils. So the palentine tonsils are located here lateral to the level of the aural pharynx. So the palentine tonsils are here. In fact, the reason they did the surgery on this patient is that they wanted to do a tonsillectomy. But when the surgeons looked down into the back of the pharynx, they saw something pulsating. So the reason they got the CT in this case was to see whether or not there was a wandering carotid artery, because that would be important here when they were doing their tonsillectomy. Well, I have 70 questions here. Thank you for your questions. How to differentiate intramural hematoma and dissection on MR. That's a really good question. The only way I can say that the the dissection obviously is going to slowly face the carotid artery immediately. I don't know if we can really differentiate a true intramural hematoma from a dissection. I think if we can differentiate clot and we can differentiate intraluminal clot because then you're going to actually see the clot in a regular margin of the lumen flow void from the intraluminal clot. But as far as intramural hematoma and dissection, I don't at least I can't differentiate between those two. The next one is is there a cutoff point to be sure that the carotid space lesion is malignant or benign. So that is an excellent question. We overall if you're trying to separate a benign versus malignant lesion if you just see a distinct lesion that's maybe two centimeters or something like that. The size criteria doesn't help. But what can help is the following is that sometimes we will see oftentimes are on a brain MR. We will actually see little lesions rounded lesions in the product land there somewhere between seven eight or nine millimeters are solid and they're bright on T2. And so you're not sure whether it's a very very early pleomorphic adenoma or whether it's a worthens tumor whether it's a lymph node. In general, what we do is that we use 10 millimeters. So, if I see a lesion, especially an asymptomatic patient incidentally on a brain MR and I see a lesion that's less than 10 millimeters, then I will just ascribe that to an intra parotid lymph node. If I see something that's 10 millimeters or 11 millimeters or 15 millimeters, then I would recommend build bringing the patient back for further imaging. So for me, that 10 millimeters is the cutoff between a lymph node and a primary intra parotid lesion. Another question here level 234 in which compartment are they in. So the level 23 and four lymph nodes are in the carotid space. The carotid space is also the post styloid paraphernal geospace. So the levels 234 are in what I referred to as the carotid space. But if you use the term post styloid paraphernal geospace. That's exactly right. So another one asked one of my favorite questions and I'm so glad they're asked they asked it. Is the floor of the mouth the same as the sublingual space and the answer is yes, 100% because if I was giving a talk and maybe I'll give this one day if you guys will allow me if I give a talk on the oral cavity and the oral fairings, then I will refer to the sublingual space as the floor of the mouth. But because I'm giving a talk on the spaces and I will call this the sublingual space. Can you demonstrate the mylohyoid muscle on CT. Yes, you can. Let me see if I can get a CT scan. Let's see. I think I know where that's located. Give me a second. There we go. So for the person that asked that question. So here's the mandible here. This is the mylohyoid muscle here. This is the mylohyoid muscle here. This is the mylohyoglossus muscle. So the mylohyoid muscle is just deep to the ramus in the mandible and directly attaches to the inferior the cortex of the lingual cortex of the mandible. I think we got I have two more minutes left. Is that right, Ashley? Yes, sir. Two more minutes. So if the cystic mass is, do you think about in the midline and sublingual space? It's a great question. So here's the scoop is that midline cystic mass is involving the four mouth. If it's anterior midline, it's an epidermal. If the cystic mass is located in the tongue base and it's midline, then that is located in the thyroid. This is the mylohyoid muscle duct cyst because the thyroid glass of duct cyst arises in the frame and seek them, which is located in the tongue base. Okay, here's a question. Someone asked me, what's my favorite space? What's my favorite space? Typically it's a bar. So, but that's not part of the lecture. So I'm sorry about that. I'm going to ask the infertemporal space versus the masticator space. That's a great question. So the masticator space has essentially replaced the term infertemporal fossa. So one of my jobs I mentioned this in the last lecture is I was a radiology representative for the staging criteria for the AJCC. We replaced the term infertemporal fossa with masticator space. So the infertemporal fossa is essentially the same thing as the masticator space. And here is another great question here. It says, can you please replete carotid vessel displacement on the basis of the mass? So I think that's a fantastic question. Let me stop there, Ashley, because I know we're going to run out of time and I want to be respectful of everyone's time. What I'm going to do here is that here's the carotid artery that's located here. If the carotid artery is displaced anteriorly, the majority of the time the lesion is going to be arising from the carotid space. If the carotid artery is displaced immediately, the majority of the times the lesion is going to be arising from the carotid space. If the carotid artery is displaced posteriorly, then it's going to be arising from the paraffaryngeal space. And if this carotid artery is displaced immediately, excuse me, if the carotid artery is displaced laterally, then it's going to be arising either from the pre-raterial space or potentially the retrofaryngeal space. There are four ways to do it and I'll do it one more time. Superior displacement is from the carotid space. Inferior displacement is from the paraffaryngeal space. Lateral displacement is going to be a retrofaryngeal space or pre-raterial space, or the medial displacement is going to be from the parotid space. So I probably should stop there. Again, thank you very much for everyone. I'm getting all sorts of what's apps and we chats. And so for me, it means so much for you that you take your time. I know everyone's on different time zones, but thank you very much. I'll turn it over to you, Ashley. Thank you so much for joining us today. Dr. McCurgy, I'm sorry if we did not get to your questions today. Thank you also to all of you for participating in this noon conference. There's been many questions about how to access this and other noon conferences. They are made on demand on MRI online.com. There is also, you can also sign up for future noon conferences there on Monday, April 6th at 12pm Eastern standard time. Dr. Daniel Ortiz will be joining us on the topic of managing COVID-19 in a low resource endemic hospital, how we do it. Please check on social media and online and register for our future noon conferences. Thank you so much and have a great day.