Lumbar Synovial Cyst

Abstract

A 48-yr-old man developed insidiously stabbing pain in the right posterolateral thigh and calf over a 7-mo period. Symptoms progressively worsened, accompanied by intermittent numbness in the same distribution. He denied weakness and bowel or bladder dysfunction. Aggravating factors included standing, walking, prolonged sitting, and Valsalva maneuver. Supine lying alleviated his pain. On physical examination, the patient had 2+ symmetric patellar and Achilles reflexes, normal 5/5 lower limb strength in all major muscle groups, and intact vibratory, light touch, and pinprick sensation in all lower limb dermatomes. Bilateral seated and supine straight-leg raises were negative. Magnetic resonance imaging demonstrated normal vertebral body height, alignment, and marrow signal. On T2-weighted images, L4-L5 disk dessication was noted. Severe facet joint arthropathy was present at L4-L5, associated with a synovial cyst extending medially, causing moderate central canal stenosis and compromise of the right L5 nerve root (Fig. 1). L5-S1 mild facet arthropathy was also noted (Fig. 2).FIGURE 1: T2-weighted magnetic resonance image of lumbar spine, axial image. A large synovial cyst arising from the right facet joint causes marked indentation of the thecal sac with nerve-root deviation.FIGURE 2: T2-weighted magnetic resonance image of the lumbar spine, sagittal image. L4-L5 synovial cyst is seen.The patient underwent a trial of neutral-based spine stabilization exercises, nonsteroidal anti-inflammatory medication therapy, and flexion/distraction manual therapy. Given the persistence of his radicular symptoms, a fluoroscopically guided L4-L5 synovial cyst aspiration was performed. At the same session, this was followed by an intraarticular right L4-L5 facet lidocaine/corticosteroid injection and a selective segmental right L5 epidural. Two weeks after aspiration and injection, the patient reported an 80% reduction in right leg pain, a marked improvement in function, and an ability to perform stabilization exercises. Eight weeks after the procedure, continued functional improvement was noted. Synovial cysts most commonly involve the joints of the limbs. Intraspinal synovial cysts are found uncommonly. They can serve as a cause of lumbar radiculopathy and low back pain. The pathogenesis of lumbar zygapophyseal joint cysts is unclear, but most cases are related to degenerative changes. There seems to be a relationship to abnormal and increased motion of the involved segment, most commonly at L4-L5, followed by L5-S1. Facet synovial cysts are frequently associated with degenerative spondylolisthesis.1 Some lumbar synovial cysts may be associated with trauma. Less common ganglion cysts can be seen in the same location but are differentiated by their lack of a synovial lining. Magnetic resonance imaging is the neuroradiographic technique of choice for imaging extradural spinal masses. A combination of its signal characteristics and site of the cyst enables an accurate diagnosis to be made on magnetic resonance imaging in the majority of cases.2 Slipman and Chow3 reported good or excellent results in 30% of patients with zygapophyseal joint cyst-induced radicular pain who were treated with the percutaneous manner above. Given the possible loculations and viscous nature of the cystic material, Lutz and Shen further recommended using a 20-gauge needle with a 10-ml syringe for aspiration.1 Surgical decompression and excision of the cyst remain the definitive treatment of choice for patients with intractable pain or significant neurologic deficit, unresponsive to nonoperative care. As synovial cysts reflect disruption of the facet joint and some degree of instability, decompression and primary fusion should be considered to improve operative results for patients with coexistent lumbar synovial cysts and degenerative spondylolisthesis.4