Synovial Facet Cyst
The facet joints are present above and below each vertebra. They are formed where the superior and the inferior articulating facets of the adjoining vertebrae meet. A synovial joint is a joint consisting of a tight fluid-filled capsule. The synovial fluid is generated by the capsule’s inner lining, which lubricates and nourishes the facet joint.
With growing age, there may be degenerative changes in the spinal column. The water content of the intervertebral disc may decrease which may lead to decreased disk height. The loss of height of the disk leads to degeneration and instability of the facet joint, known as facet joint syndrome. The bones forming the joint may rub against each other, causing pain in the lower back.
The synovial fluid formation is increased by the body to help lubricate the facet joint. At times, the extra fluid may get caught in the lining of the capsule and form a fluid-filled sac. The fluid-filled sac may encroach upon the precarious space in the neural foramen and cause pressure symptoms such as spinal canal stenosis.
The fluid buildup in the cyst occurs slowly but may happen fast if there is bleeding inside the cyst (facet cyst hematoma). The majority of the facet cyst formation occurs in the L4-L5 spinal level.
The patients may complain of low back pain. The back pain may be associated with radiating leg pain. At times, patients may complain of feeling numbness and tingling sensation in the legs. The symptoms may progress suddenly in the case of synovial facet hematoma.
Neurogenic claudication may occur in patients with synovial facet cyst. The patients may complain of pain in the buttocks and the legs, which is worse on walking. The pain is relieved at rest by bending forward. The space in the neural foramen is reduced on bending backward and standing. The effect is exacerbated with a synovial facet cyst encroaching the space.
The diagnosis is made on an MRI with clinical examination eliciting nerve root defects. The physician may perform a thorough neurological test to look for the nerves’ motor and sensory function. The synovial facet cyst is visible on MRI as an MRI is able to differentiate between various soft tissue structures.
The management of synovial facet cyst is mainly conservative. The conservative management consists of nonsteroidal anti-inflammatory medications to relieve pain and inflammation. Physical therapy is initiated to improve muscle strength and flexibility. Heat and cold therapy may help relieve the pain and stiffness in some patients.
Epidural injections may also help in the temporary control of pain. In patients where the symptoms clearly correlate with the synovial facet cyst, a CT guided cyst rupture and cyst steroid injection may be done. Repeat injections may be required in some patients.
Operative management is indicated in patients with persistent symptoms despite conservative management. Surgical management may be done in the form of lumbar laminectomy and decompression. The surgery consists of creating an opening in the lamina and the facet joint to take out the cyst. Laminectomy and decompression surgery are generally done in patients with unilateral symptoms.
Facetectomy with fusion surgery is the treatment of choice when indicated. The surgery is indicated in patients with bilateral symptoms, recurrence following laminectomy and decompression, and central canal stenosis.