 Thank you so much for sharing your lecture with us today, Dr. Resnick. At this time, we will open the floor for any questions from our audience. So we do have quite a few already in the Q&A chat box. What is your feeling about HIZ and disc disease, chronic versus dramatic? I see this so commonly it appears that they are chronic. So again, like that, you're talking about high intensity zones. Is that what they, is HIZ they said? Yes. Yeah. So basically, that was a classic term that we used to use for right signal involving the annulus fibrosis of the vertebral disc, particularly posteriorly, which some people suggested might in fact predict that there was going to be a disc vertebral dis-displacement. I have not seen that particular finding as very useful in differentiating among the various inflammatory diseases or infectious diseases or degenerative diseases of the intervertebral disc. Thank you so much. How to differentiate degenerative form from trauma vertebral collapse and settings of trauma? OK, well, trauma is a very interesting aspect of things that occur at the disc over a people junction. One of my interests has always been, for example, what is produced as schmall's nodes or cartilaginous nodes? And probably one of the most common causes of that relates to micro trauma occurring at the disc over a people junction, allowing this material to enter the vertebral body. And that's why I suggested perhaps the Anderson lesions that we would see in ankylosing spondylitis might be explained by schmall's nodes, particularly if you have facet disease, you have an unstable spine, you have abnormal motion at the disc over a people junction. And so schmall's nodes may enter into the vertebral body. I don't think collapse vertebral bodies is something that I think of very often with any of the conditions that we spoke about today, degenerative or inflammatory in nature. Thank you so much. How to differentiate dish versus AS and the criteria? Yeah, it was interesting. There have been many articles written about dish since we just used that term back in, I guess it was in the 1970s when I was about five years old. And basically, we came up with some criteria that people have debated since. And one of them was, in fact, the involvement of four contiguous vertebral bodies. And so I wanted to emphasize that was a purely arbitrary, arbitrary finding. We also emphasize, in fact, that you didn't see infararticular bone fusion in dish as opposed to ankylosing spondylitis. But there have been articles since that have indicated that the degree of bone fusion may occur in dish could be at one particular disc over people junction early on. I'm sure it is. And in those cases, it can be difficult differentiating it from ankylosing spondylitis. I think early on it would be difficult. But once you get to the pattern of flowing ossification, I think it becomes easier to separate it from not only ankylosing spondylitis, but psoriatic involvement of the spine as well. And then finally, with regard to the SI joint, most patients with dish who have fusion of the SI joint, when you study that with CT, you'll see that it relates to osteophytes around the periphery of the joint and not bone fusion in the central aspect of the joint. So that allows you to distinguish it from ankylosing spondylitis. Thank you. Does the shiny corner sign occur only in AS? That's interesting. The answer is no, because what it relates to is an anthocytus. And indeed, anthocytus can be seen in psoriatic involvement of the disc over people junction reactive arthritis as well. And in some cases of degenerative disc disease, the pattern of bone sclerosis, for example, an inter vertebral osteocondrosis may not be diffused, but may involve a corner of the vertebral body. But in general, it's a great sign. It's a great sign, particularly when it's combined with squaring of the vertebral bodies and early syndesmophic formation. When you have that combination, I think you'd be pretty sure you're dealing with ankylosing spondylitis. Thank you so much. Is the stepladder appearance of rheumatoid and any way related to facet joint involvement? How are facet joints impacted in rheumatoid? Yeah, and that's a good question. I did not get into a discussion of facet joint disease very much in this lecture, but clearly many of the diseases that I spoke about will in fact involve the facet joints. For example, osteoporosis of the spine may predominate within the facet joints with now and bone sclerosis and osteophytes. And certainly degenerative diseases may involve the facet joints and posteropost disease, for example, Bastrup's disease. In ankylosing spondylitis and in rheumatoid facet joint involvement is common and can be significant. And some people believe that it is an early manifestation of ankylosing spondylitis that the facet joints are involved prior to discovertival involvement. In fact, there's a link between facet joint involvement and discovertival changes in ankylosing spondylitis. When you have bad facet disease, the abnormal motion that occurs at that discovertival junction may prevent syndesmophile formation from occurring. Syndesmophiles predominate where you don't have a lot of facet joint disease. Thank you so much. Do you grade SI joint disease with MR? We do, I kind of mentioned that we do not use MR a lot in our practice, our clinicians for sacroiliitis. And fortunately, a lot of the pictures that I showed you were sent to me from some of our previous visiting scholars from Brazil where they were doing a lot more of MR. So we are not doing it. Now, I happen to think, again, you remember, I grew up in the age of conventional radiography. And I think if you get AP views of the sacroiliac joints angled about 20 degrees toward that head that elongates the sacroiliac joint, I think we're pretty good at diagnosing early sacroiliitis in those particular diseases. Where I think MR is most useful is in following patients with sacroiliac joint involvement during therapy, because you can see a decrease in the inflammatory reaction and the change to that fatty infiltration that I talked about. Thank you so much. Have you seen psoriatic arthritis without skin lesions? Yes, I have. I also have seen cases where the clinician says there's no skin disease. We see imaging findings that suggest psoriasis. The clinician goes back and finds a little patch of psoriasis, perhaps the hairline, that he or she did not notice before. But you can have the skeletal abnormalities before you have obvious skin abnormalities. Thank you so much. There's been some debate about what represents the best MR sequence for identifying SI joint erosions. What do you believe is the best sequence? So as I said, in the cases that we've done and based on the literature that I've read, I think you should have two particular sequences. One would be a T1 weighted sequence. The other could be either a stir sequence or a fat suppress fluid sensitive T2 weighted sequence. And I think you should do that in two imaging planes, as I mentioned, in the coronal plane to the sacrum and in the right angle to those planes. Now, there are reports that it might be valuable to do larger field of view imaging, including a whole body imaging because of you can pick up endocytus, which is common in patients who have spondyloar apropathy. You can pick up the facet joint disease, et cetera. But we have no experience in the whole body imaging in patients who have ankylosis spondylitis. Thank you so much. Can bone mastasis be T1 and T2 black without bone edema? Is because you say that again, please? Yes, it's kind of bone mastasis. The T1 and T2 black without bone edema. Is that bone metastasis? Yes, I just can't pronounce the word. The answer is yes, but unusual. All right, I think, as you know, we think of carcinoma, the prostate in particular. I know there's a long list of other primaries that can lead to sporadic metastasis. But carcinoma, the prostate, I had seen examples where there is mainly low signal on T1 and T2 weighted images. And so the answer to that is yes. But in most cases, there is, in fact, a reaction around the metastatic deposit that will have high signal. Thank you very much. Is spondylitisis and introvertible osteocrondosis the same entity? No, I hope I made that clear. Introvertible osteocrondosis is degeneration. It is degeneration that begins in the nucleus propulsus of the introvertible disc. And spondylitis is an inflammatory reaction, which is totally different. Thank you so much. How to differentiate an imaging infection from early unilatera sacrolitus? OK, I think they want to know, and by that question, is an infection, discovertible infection, simulate discovertible changes in spondylitis? And the answer is yes, it can. For a number of reasons, some of which I kind of illustrated that the Anderson lesion can look very much like infection. So infection can look very much like an Anderson lesion. And the improper fracture healing that occurs in late stages of ankylosing spondylitis can look a lot like a discovertible infection. So the answer is yes, there are overlapping features. And what I found most useful is to study elsewhere in the spine. Now, I've got to be honest about it. I have seen over the years ankylosing spondylitis of the spine with a discovertible infection as well. But when I have a patient with ankylosing spondylitis with a rose of disease and a discovertible junction, I favor it as not infection. If the clinician says, well, we're really worried about it, then we'll go ahead and biopsy or aspirate to prove it is not infection. Thank you so much. And I appreciate you bearing with me with my pronunciations. How do you refer to rheumatoid changes of the C spine versus multi-level degenerative spondylitis, an OA? Yeah, so once again, I'd love to tell you we have rules that will make 100% accuracy in all of these differential diagnosis. But if I tell you that I am lying, I certainly have cases where I struggle. And I think I certainly can struggle in patients who have rheumatoid involvement, involved in the cervical spine that can look like degenerative disease of a disc. But one of the interesting aspects that I look for that I tried to emphasize was that some patients who have rheumatoid who have discovertible erosions, beginning at the joints of lusca extending across the disc, will not have prominent osteophytes. And because of that, if I see extensive discovertible erosion without any osteophytes, I always think of rheumatoid arthritis as a possibility. So again, in degenerative disease, remember there are two types of degenerative disease that I call the interlaseous space. Part of that space is occupied by a synovial joint. Degeneration within that joint, the sacroiliac joint, is called asterothorosis or asterothritis. The main features are joint space snarling, vacuum phenomena, and a sclerotic line or a small band of sclerosis, particularly on the ilio aspect of the joint, combined with osteophytes. And I showed you one that looked like carcinoma, the prostate metastatic develop. When we deal with sacroiliatus, there is erosive disease. There's initial widening of the sacroiliac joint. The band of the sclerosis is border and less defined. And I think those features, in most cases, will allow you to make a differential. Now, I can tell you a couple other points about that differential. I did not talk about osteitis condensants, ilio. And as you know, that's classically a disease of multiparous women, kind of rarely occur in men where you get very well-defined sclerosis, triangular in shape on the ilio aspect, with little or no sacral involvement. So I think in those cases, sometimes you run into a differential with ankylosing with sacroiliatus. And then one other point I would make, if you read the recent literature over the last five years of the value of MR in diagnosing sacroiliatus, you will see many examples of other diseases that on MR can simulate the sacroiliatus of ankylosing spondylatus. So there is a differential diagnosis for the MR imaging features. And I'll give you one example. Post-pregnancy, the mechanical changes that occur in the sacroiliate joint on MR can simulate sacroiliatus.