This post will be a little different in scope than my usual ones, but I am excited about it nonetheless. One of you out there (LPC) recently posted an article about high-resolution ultrasound (HRUS) as an imaging modality for the lesser occipital nerves. I first want to say congratulations for posting this article. It is so wonderful to see people educating themselves in this manner. Of course, I immediately went and pulled the whole article myself, read it including several of the cited references and have a few thoughts. These points are not meant to be pejoratively critical; quite the contrary, I commend the authors on using this new modality in a novel way and think/hope their efforts will continue so that it may be available to many people in the future. So here goes….
1.)HRUS certainly looks promising as an imaging modality, but also has a few drawbacks. The technology requires a user with many years of experience, because even in the images demonstrated, the structures that are noted to be the LON and the surrounding muscles are not exactly clear. Two, as any formerly pregnant woman would tell you, US imaging often requires moderate pressure on the area being imaged to optimally delineate the structures being sought out and if you have ON, this pressure might be prohibitive. Three, likely one of the reasons even simple US is not used more commonly is that the companies selling these devices charge a hefty premium for them. I would guess that a HRUS machine would likely run between $85,000 - $150,000 or more making it a prohibitive purchase for most practices, especially when insurance reimbursements are decreasing. Hopefully as then technology improves and more studies demonstrate their utility and accuracy, costs will come down and you’ll see more of these machines around.
2.)The authors describe several patients in whom they sonographically identified lymph nodes as possible compression structures for the LON, but I can personally attest that after many such cases, I rarely find a lymph node in my travels and dissections. This experience is vetted by the published literature from Dr. Guyuron cited in the article. I would therefore, wonder if what the authors presume is a lymph node is actually another structure. The authors also don’t mention any vascular compression which I have seen on a number of occasions (perhaps a function of this being a new modality for a new application - see above). Future studies will tell.
3.)It is hard to tell how far cranially and caudally the authors went in imaging the LON. In other words, I would wonder if you could image the nerve behind the sternocleidomastoid muscle as I have found fascial bands in that area which compress the nerve. Therefore a negative HRUS may not mean there is no compression, as is the case with any diagnostic modality. Having said all of the above, I really believe that HRUS has potential to be a wonderful adjunctive imaging modality. As peripheral nerve surgeons, we could use it to visualize structures pre-operatively and perhaps help in diagnostic blocks as well as in following patients post-operatively, both those who improve (you can see if their nerves change in imaging characteristics post-op) as well as those that don’t.
4.)Finally and most importantly, this article appears in the journal Cephalalgia, an important clinical neurology publication and one, I believe, associated in some way with the International Headache Society. The manuscript and others like it that are slowly appearing in such journals represent some acceptance of the peripheral nerve compression paradigm as a cause for headaches. Many of the cited references are from articles by peripheral nerve surgeons. Hopefully this acceptance will expand as more such articles come out. Furthermore, I believe that credit for this progress comes in large part secondary to the efforts of the people in forums like this one. As you search for answers yourselves, you will find a lot of good and reliable information and I encourage you to share that information with your other treating physicians. The good ones will appreciate it. Kudos and keep up the good work. For more information, please read some of our other blog posts and follow us on Facebook and Twitter, and check out some of the available resources on www.peledmigrainesurgery.com to learn more.