Lumbar synovial or ganglion cysts.

Most reports regarding synovial cysts of the spinal canal have been presentations identifying an unusual pathological entity that is to be included in the differential diagnosis of cauda equina compression syndromes. Most of the 26 cases reported represent isolated examples of this pathological process. We present five cases of lumbar synovial cysts encountered in our practice in the past 8 years. Patients with lumbar synovial cysts do not demonstrate any predictable clinical picture. They may present with a unilateral sciatica or neurogenic claudication. Lumbar extension is usually restricted, whereas flexion is full. Mechanical signs of nerve root entrapment or lumbosacral plexus irritation are unimpressive. Neurological deficits are usually mild, if present. Radiological findings include degenerative spondylosis, spondylolisthesis, and a rounded posterolateral extradural mass of low attenuation value adjacent to a facet shown on computed tomographic scan. The etiology of lumbar synovial cysts is not known. Histological findings of myxoid degeneration, microcystic change, calcification, and hemosiderin deposits suggest that chronic microtrauma with occasional focal hemorrhage may play a major role in the etiology of the cysts. With resection of the cyst, the postoperative course is usually uneventful. Recurrences have not yet been encountered in our patients.