Synovial Cyst

What is a Synovial Cyst?

A synovial cyst refers to a small, abnormal fluid-filled lump that develops along the spine ¹. These cysts often remain asymptomatic for a long time and usually benign (non-malignant) and non-cancerous in nature.

A Synovial Cyst typically forms due to degenerative changes in the spine’s joint. They can develop around any joint in the body. However, over 90 percent of synovial cysts occur in the facet joints of the lumbar spine ².

What are the causes and risk-factors of Synovial Cysts?

The actual causes of synovial cyst formation remain unknown. A recent study shows that a damaged facet joint produce more synovial fluid than a healthy joint. This fluid provides lubrication and helps to avoid friction between the joint. However, a cyst may form when extra fluid produced by the joint builds up inside of the synovial sac.

Synovial cyst mostly occurs in older adults (over 65 years old) because of the degeneration of the facet joint in their spine. Peoples under 50 years of age will rarely develop a synovial cyst. Patients with joint conditions like rheumatoid arthritisprone to develop a synovial cyst.

Symptoms of a Synovial Cyst

Symptoms of a synovial cyst depend upon the size and the location of the cyst. Some patients with a synovial cyst may not experience any signs or symptoms ². However, people with a synovial cyst may suffer from the following one or more symptoms:

• Severe pain in the lower back
• Difficulties in walking and standing
• Numbness, or tingling in one or both legs because of spinal stenosis
• Radiating pain in one or both legs and foot, known as sciatica
• Weakness of muscle in both legs
• Loss of motor function in legs
• Cramping, weakness, or heaviness feeling with pain in one or both legs, known as neurogenic claudication
• Temporomandibular joint pain and reduced mouth opening in case of cyst present in this region ³;
• Rarely, cauda equina syndrome may develop because of synovial cyst

How do Neurosurgeons diagnose Synovial Cysts?

The initial diagnosis includes a clinical presentation and pain patterns of patients ⁴. Doctors may further confirm by:

• X-ray imaging (known as plain film): Flexion or extension motion x-rays;
• Magnetic resonance imaging (MRI);
• Computed tomography (CT) scan; and
• Ultrasonography;

What is the treatment of a Synovial Cyst?

Non-surgical treatment option for a synovial cyst include:

• General observation and modification: If the cyst produced no pain, your doctor may suggest leaving as it is and no medical treatment requires for this condition;
• Pain medications like non-steroidal anti-inflammatory drugs such as acetaminophen and ibuprofen can reduce pain caused by a cyst;
• Application of cold or hot therapy may relieve pain and reduce swelling;
• One or two-hour rest can help for a short time during a day;
• Steroid injection can use as a temporary pain reliever and a facet injection may use to drain out the synovial fluid;

If these non-surgical options may not help you, your physician can go for further surgical treatment ⁵. This method removes the cyst along with their root permanently. After removing the cyst, surgeons need to fuse the affected joint to prevent recurring of the cyst such as lumbar fusion surgery.

References

1. Wang J, Shao J, Qiu C, Chen Y, Liu B. Synovial cysts of the hip joint: A single-center experience 11 Medical and Health Sciences 1103 Clinical Sciences. BMC Surgery. 2018;18(1):1–5. doi:10.1186/s12893-018-0450-z
2. Splavski B, Rotim A, Brumini I, Koprek I, Gajski D, Božić B, Rotim K. Lumbar Spine Synovial Cyst: a Case Series Report and Review of Surgical Strategies. Acta clinica Croatica. 2019;58(3):491–496. doi:10.20471/acc.2019.58.03.13
3. Maribo Y, Stokbro K, Aagaard E, Larsen SR, Thygesen T. Synovial Cysts in the Temporomandibular Joint: a Case Report and Critical Review of the Literature. Journal of Oral and Maxillofacial Research. 2019;10(1):1–9. doi:10.5037/jomr.2019.10104
4. Epstein N, Baisden J. The diagnosis and management of synovial cysts: Efficacy of surgery versus cyst aspiration. Surgical Neurology International. 2012;3(4):157. doi:10.4103/2152-7806.98576
5. Bruder M, Cattani A, Gessler F, Droste C, Setzer M, Seifert V, Marquardt G. Synovial cysts of the spine: Long-term follow-up after surgical treatment of 141 cases in a single-center series and comprehensive literature review of 2900 degenerative spinal cysts. Journal of Neurosurgery: Spine. 2017;27(3):256–267. doi:10.3171/2016.12.SPINE16756