Ultrasound was started by Karl Dussik in the 1930s and’40s and he was trying to diagnose intracranial tumors. Things have progressed extensively over the last several decades and so ultrasound is now being used to help locate peripheral nerves and to help coordinate injections and to even show some improved potential outcomes in safety when it comes to trying to help patients with chronic pain. What’s nice about ultrasound is that it can show the surrounding tissue and it can also show vasculature, as well as the actual nerves themselves.
Although CT and fluoroscopy are considered the gold standards, and fluoroscopy is typically used in outpatient-based procedures, fluoroscopy is really only good at showing bone and bony structures and not necessarily the actual targets that you’re looking for.
We think we know where that nerve should be, based on anatomical dissections and what we know of the anatomy, but everyone’s a little different and ultrasound can actually show that. You can use ultrasound pretty well with a lot of different types of injections and therapies for patients with chronic pain. There are certain types of injections for which the evidence is lacking. So for the typical epidural steroid injection, you can’t really see the spread of your local anesthetic, and so it’s not been very well considered for use in these types of situations.
There are other situations where it can be very useful, especially in the neck-type region, such as for cervical medial branch blocks or third occipital nerves or greater occipital nerves--there’s been very good evidence because the anatomy is favorable and it’s more of a superficial injection. Also in terms of sympathetic blocks, the stellate ganglion has been very well studied in ultrasound and you can avoid hitting vasculature, which you would normally have to do if you go through the classic approach using fluoroscopy. Typically, you have to go through the thyroid tissue which is pretty vascularized. You can avoid that using ultrasound-guided techniques.