What is a Synovial Cyst?

A synovial cyst is a sac that's filled with fluid your body produces to lubricate joints (synovial fluid). These cysts may form in the
lower (lumbar) portion of the spine when the spine's facet joints begin to deteriorate due to degenerative diseases, such as arthritis. Located behind the vertebrae, there are two facet joints at each level of your spine. The facet joints connect one vertebra
to another. They stabilize the spine while still allowing flexibility.

Arthritis and other degenerative diseases can cause changes in the facet joints and their lining (synovium) that result in the
production of excess synovial fluid. This fluid can build up within the synovium of the joint and create a synovial cyst. The cyst
may, in turn, place pressure on nearby nerve roots within the spinal canal, resulting in low back and lower limb pain among
other symptoms.

Treatment of a lumbar synovial cyst depends on several factors. If your symptoms aren't bothersome and don't disrupt your daily
routines, you might not need any treatment. Exercise and activity modification may be enough to relieve discomfort. Your doctor
could also recommend monitoring the cyst periodically with an imaging study, such as an MRI, to check for changes. If your symptoms are interfering with daily life, draining the cyst with a small needle (aspiration) may relieve pain and discomfort.
A neuroradiologist — a physician who specializes in using imaging techniques such as MRI and CT to diagnose and treat disorders of the nervous system, head and spine — typically performs the aspiration procedure. Aspiration is only an option if the cyst's size and location allow the neuroradiologist to safely place a needle by the facet joint and into the cyst. Although aspirating a lumbar synovial cyst may relieve symptoms, in some cases it's only a short-term solution, as the cyst may reform following aspiration. But if aspiration is a viable option for your situation, it may be worthwhile to try it, as aspiration is less invasive and less risky than surgery.

Steroid injections are another possible treatment option. Having a steroid medication injected into the facet joint or into the space surrounding the cyst can decrease the inflammation associated with a synovial cyst and reduce pain. This treatment is only temporary, however, and while it effectively reduces symptoms in some people, in others it does not provide relief. Most physicians recommend that patients receive no more than three steroid injections a year.

If your symptoms are severe, or if other treatment has been unsuccessful, surgery to remove the cyst may be necessary. In most
cases this involves decompression and removal of the cyst. In some cases, surgery may also involve fusing the affected facet joint due to recurrent cyst formation following an initial operation or if spinal instability is a concern. Fusion prevents the facet joint from moving and helps to ensure that the cyst will not form again. In most cases, surgery to remove the cyst with or without fusion is effective in treating lumbar synovial cysts, and the recurrence rate of cysts following surgery is low.

Adopted from mayoclinic.com