One very painful degenerative condition of the spine that I commonly see in my clinic is the facet cyst. These are also referred to as synovial cysts as they originate from the synovium (lubricating tissue that lines the opposing surfaces of a joint) of the spinal facet joints. While facet cysts theoretically can originate at any level of the spine, they most commonly occur in the lower lumbar spine (i.e. L4/5 and L5/S1.) These cysts typically grow from the medial (inner) aspect of the joint were they then begin to compress the traversing nerve root as it passes nearby (see figure 1.) This compression can be quite severe and, when coupled with the movement of the joint, can lead to excruciating pain (at the time of surgery I’ll often see a dent on the nerve root from the severe pressure of the cyst.) After far lateral disc herniations, this is probably the most painful non-traumatic pathology that I encounter in my clinic.
Figure 1: Sagittal (left) and axial MRI showing large facet cyst (red arrows) emanating from the left L4/5 facet joint. Note how the cyst originates from the medial (inner) aspect of the joint and severely narrows the right side of the spinal canal.)
First and foremost, facet cysts are not cancerous. Many patients equate the term “cyst” with cancer so the first thing they want to know is whether or not they have cancer in their spine (reason #146 NOT to read your MRI reports because those terms you don’t understand will FREAK YOU OUT unnecessarily.) Facet cysts are benign and simply indicate advanced arthritis of the joint from which they emanate.
The treatment of facet cysts is a bit controversial and can provoke colorful discussions at meetings of spine surgeons. Most of the controversy stems from the question of how aggressive to be with initial surgical treatment of the cysts. More on that later. For now, let’s review the treatment options of facet cysts here:
- Watchful waiting. This usually isn’t a good option for patients. First of all, most patients with this condition are in so much pain when they walk in that they want surgery yesterday. If I even begin to discuss waiting another 6-8 weeks for spontaneous resolution of their pain they look at me like I’m crazy and immediately begin looking for another doctor to provide another opinion. The problem with watchful waiting is that unlike a herniated disc fragment which can be reabsorbed by the body, facet cysts typically don’t involute spontaneously. To be fair, though, I have seen cases where the compressed nerve becomes accustomed to the irritation and becomes less painful over time without intervention. Usually, however, an invasive treatment is needed to take care of the problem.
- Interventional pain management. Here’s one of those areas of controversy; even my partner and I don’t always agree on the utility of this treatment for facet cysts. The thought is that a pain management physician can guide a needle to the cyst using fluoroscopic guidance and then aspirate the fluid within the cyst to decompress it and thus take the pressure off the adjacent nerve. There are two problems with this approach in my opinion. First, if you were to come into the OR and watch me resect one of these cysts you’d see that 90% of the time the cyst is filled with a thick gelatinous substance rather than a thin fluid that can be aspirated. It’s easy to see how this needle aspiration could fail. Second, cysts that are simply aspirated will often recur. Without removing the cyst wall the underlying structure of the cyst remains, only to fill up with fluid again later. Now, I never discourage a patient from trying cyst aspiration or an epidural steroid injection prior to committing to surgery. I certainly have seen it work. It’s just important to understand that aspirating the cyst either isn’t possible or doesn’t permanently ablate the cyst so often any symptom improvement achieved with interventional pain management is short lived.
- Surgery. When watchful waiting and/or interventional pain management treatments have been tried unsuccessfully (or if the patient is just too miserable), surgery should be considered. There is some debate on how aggressive that surgical treatment should be right off the bat, though. Some surgeons will jump straight to recommending a fusion for a patient with a facet cyst. The thought is that the presence of a facet cyst suggests that the facet joint is structurally incompetent and that without a fusion these cysts will only recur. There is some truth to this. I quote up to a 20-30% rate of recurrence for facet cysts without fusion. Typically, though, I like to avoid a fusion initially if possible. Thus, my algorithm for the surgical treatment of facet cysts is as follows (see flow chart):
- MRI shows facet cyst that correlates with patient’s pain. Patient has failed conservative management.
- If the facet cyst occurs in the setting of a spondylolisthesis (which they often do) I’ll usually offer a fusion right away (XLIF at L4/5 and above, ALIF at L5/S1.)
- If there is no concurrent spondylolisthesis I’ll check flexion-extension Xrays to evaluate for instability (I may also just do this for the patient WITH spondylolisthesis if for some reason I’m trying to spare them a fusion.) If the motion segment in question is unstable then the patient gets a fusion. If there is no instability I’ll do a minimally-invasive laminectomy to resect the cyst.
- If the cyst recurs after laminectomy the patient gets a fusion.
Lastly, and here’s where it gets really controversial, whenever I do an XLIF or ALIF on a patient with a facet cyst I no longer directly resect the facet cyst. I rely completely on indirect decompression to take care of the cyst. By using the appropriately sized spacer to restore disc height and correct spondylolisthesis, the facet cyst is essentially stretched out so that no longer compresses the adjacent nerve (see figure 2.) It’s also believed that by eliminating the motion at the facet joint with a fusion the facet cyst can then spontaneously resolve. It’s like magic. This always makes the patient nervous though. They always want to know why I’m not cutting that painful cyst out to be sure it’s off the nerve. What I tell them is that I know, after looking the data on all my patients, that in just about every case the height restoration provided by the spacer is enough to decompress the nerve (there’s less than a 5% chance of failing indirect decompression in our experience.) Also, these cysts are usually densely adherent to the underlying nerve and dura. Dissecting these cysts off of the dura can be quite treacherous and the rate of dural tear and cerebrospinal fluid (CSF) leak in these cases is not insignificant (5-10% in our hands). Thus, why would I subject the patient to the risk of CSF leak (not to mention the risk of spending the extra time under anesthesia that it takes to do the laminectomy) that is greater than the risk of them failing indirect decompression? As we’ve discussed previously: believe in indirect decompression!
Figure 2: Preoperative (left) and postoperative MRI images showing a patient with a left L4/5 facet cyst (red arrow) and spondylolisthesis that was treated with XLIF and percutaneous pedicle screw fixation (NO direct cyst resection.) Patient’s leg pain was relieved immediately after surgery. Note on the postop MRI (taken about 3 months after surgery) that the facet cyst has disappeared.
Thanks for reading!
J. Alex Thomas, M.D.