Synovial Facet Cyst

The human spine is formed by individual vertebrae and connective tissue discs in between. The vertebrae form the spinal canal. There are seven cervical, twelve thoracic, and five lumbar vertebrae. The intervertebral discs are the link between the individual vertebral bodies.

The little joints that link the vertebrae together are known as facet joints. They help to stabilize the spine and, together with the intervertebral discs, allow a certain degree of mobility of the spinal cord. The spinal canal should be wide enough to allow nerve roots to float freely in cerebrospinal fluid. The front border of the spinal canal is built by the vertebral bodies and intervertebral discs, the side by the intervertebral joints (facets) and back by the ligamentum flavum (yellow band) and vertebral arches. Discs consist of an outer fibrous ring (annulus fibrosus), which surrounds an inner gel-like center (nucleus pulposus). The spinal cord and nerve roots lie within the spinal canal. The spinal cord extends downwards approx. to the 1st lumbar vertebra. Below, only nerve roots are present in the spinal canal. At the level of the intervertebral disc the nerve roots pass through the neural root foramina to exit the spinal canal. The spinal cord and nerve roots conduct electric-like signals from the skin and joints to the brain, and process of movement is initiated from the brain to the muscles.

Synovial cyst is a benign cyst (a fluid-filled sac) arising from the facet joints of the lumbar spine due to degeneration. They usually cause chronic presure on the nerve roots. Rarely, intracystic hemorrhage in the cyst may cause acute compression of one or more nerve roots.

Gradually progressing compression of one or more lumbar nerve roots in the recessus/root canal

Tingling, shooting pain or muscle weakness (paresis) of one or both legs

The treatment may be non-surgical or surgical. Minimally invasive methods like percutaneous steroid injection and percutaneous cyst rupture improve the symptoms in about half the patients (PMID: 27683703). The rest of the patients usually require surgery to achieve long-term relief of symptoms.

Elective surgery should be considered when compression of a nerve root causes a significant muscle weakness (>72 hours) is present or the symptoms (e.g. pain) impair the patient’s quality of life and conservative treatment fails to achieve significant improvement within 6-8 weeks.

To release the compressed nerve roots

To improve symptoms (e.g. pain reduction)

To stop the worsening of the symptoms

To preserve the protective function of the spine

Posterior decompression of the spinal canal without fusion