Synovial Cyst

A synovial cyst describes a benign fluid filled sac located in a synovial joint – such cysts may occur throughout the body, however adverse symptoms more commonly present as a result of lumbar synovial cysts which have extruded into the spinal canal.

What Can Cause a Synovial Cyst?

Spinal synovial cysts often manifest in the L4/5 region of the lumbar spine, a particularly flexible area of the spine – they are rarely found in the thoracic and cervical regions.

Synovial cysts are typically associated with facet joint arthropathy; degenerative changes, such as osteoarthritis and spondylolisthesis, affect the spinal joints, causing a breakdown of cartilage and other tissues. Such changes are due to the ageing process, most commonly occurring in the 6th decade of life, with a very slight female predominance.

The facet joints are located between the bony projections at the back of the vertebrae, they are covered by a thin film of tissue referred to as the synovium, which produces lubricating fluid. Changes to the facet joints as a result of ageing and the wear and tear process, can cause degeneration. In response, the body produces additional fluid in an attempt to protect the joint from further damage, in some people this excess fluid may be retained within the synovium, creating a sac like protrusion described as a synovium cyst.

Other systemic diseases such as rheumatoid arthritis, which can affect the joint, are also associated with the degeneration of the facet joints.

Symptoms

The growth of epidural cysts into the spinal canal can provoke compression or irritation of nearby neural structures. Any associated symptoms will depend very much on the size and location of the synovial cyst. If the cyst is large enough, it can cause significant narrowing of the spinal canal, provoking symptoms of spinal stenosis and in rare cases, symptoms of Cauda Equina may develop. Cauda Equina is a medical emergency requiring immediate attention, if left untreated it may cause irreversible damage and paralysis.

Synovial cysts of the lumbar spine can cause a wide range of neurological complaints including unilateral (or bilateral in rare cases) radicular pain, numbness, weakness and tingling of the legs, drop foot, neurogenic claudication, which may present as pain and cramping in the legs with difficulty walking or standing, as well as localised pain in the lumbar spine itself. Spinal instability due to the degeneration of the facet joints may also be present.

Symptoms often ease when the patient is in the seated position, this is because the spinal canal narrows slightly when in a standing position.

Diagnosis

Diagnostic imaging techniques such as MRI (usually the preferred method) and CT Scans are helpful in identifying synovial cysts and spinal stenosis, X-Ray may also be used to ascertain the stability of the spine – it is important to identify any spinal instability if surgical removal of the cyst is being considered, as the instability should be addressed at the same time as the surgery.

Treatment

Synovial cysts are only treated when symptomatic – some people may have a synovial cyst yet be unaware of it.

Conservative treatments

A course of pain relief medication is likely to be the first course of action, this will typically include over the counter medication such as analgesics (paracetamol) and NSAIDS (ibuprofen, asprin). This type of medication is helpful at reducing painful symptoms without the risk of causing dependency, as can often be the case with other stronger prescription based medication such as opiods.

Corticosteroid Injections

In some cases an injection of steroid and anaesthetic may be helpful to provide short term relief of painful symptoms and reduce swelling.

Surgery

Surgical management may be considered in the case of a clear diagnosis and when all conservative methods have failed. The main aim of surgery is to relieve the compression by removing the cyst and creating more space in the spinal canal. Decompression surgery with or without fusion, depending on the associated instability, aims to remove the cyst and decompress any affected neurological structures. Minimally invasive surgery with excision of the cyst may be viable in some cases, this type of surgery minimises the effects of soft tissue trauma and blood loss as well as recovery time.

Pain Management

The pain management clinic devices a comprehensive treatment program which often incorporates a variety of different treatments to be used simultaneously. The pain management team is multidisciplinary, consisting of pain management consultants, surgeons, physiotherapists, psychologists and other health professionals, to help treat symptoms and manage chronically painful conditions.

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