Larger anular defects and less disc removal increased the risk of reherniation. Greater volumes of disc removal were associated with accelerated disc height loss. In the setting of larger anular defects or less aggressive disc removal, concern for recurrent herniation should be increased during outpatient follow-up. In this situation effective anular repair may be helpful.

In patients at high risk of herniation recurrence after lumbar microdiscectomy, annular closure with a bone-anchored implant lowers the risk of symptomatic recurrence and reoperation. Additional study to determine outcomes beyond 2 years with a bone-anchored annular closure device is warranted.

Objective-Synovial cysts of the vertebral facet joints are a source of nerve root compression. DiVerent surgical procedures are in use, but no consensus has been formed so far as to which method should be used in synovial cysts. To clarify the role of surgical management, the eYcacy of operative procedures and factors influencing the outcome in our own series of 19 patients treated between 1994 and 1998 were analysed. Methods-Nineteen patients with a mean age of 65 years underwent surgery for medically intractable radicular pain or neurological deficits caused by synovial cysts. The patients' records were retrospectively analysed for neurological deficits, cysts diameter, operative approach, segmental hypermobility, and clinical outcome; CT and MRI were analysed for additional degenerative changes. Results-In 17 patients an excellent result and in two patients a good postoperative result was achieved. Twelve patients were found to have hypermobility of the facet joints and six had spondylolisthesis. There was no correlation between cyst diameter, operative approach, and outcome. No intraoperative or postoperative complications occurred. Conclusions-Age and hypermobility may play a part in the aetiology of facet joint synovial cysts. As all operative strategies showed equally good clinical outcome, total excision via a small flavectomy as the least invasive approach should be considered therapy of choice in patients with cysts causing neurological deficits. (J Neurol Neurosurg Psychiatry 2001;70:74-77) Keywords: facet joint; flavectomy; lumbar spine; spondylolisthesis; radicular pain; synovial cyst Space occupying lesions of the spinal canal often cause radicular pain or neurological deficits and are most commonly caused by either disc herniation or a bony stenosis of the spinal canal. In a few cases pain in the leg and accompanying paraesthesia is caused by neurinomas or inflammatory processes. A rare source of extradural mass eVects are cysts of the facet joints (accounting for an incidence of 0.8% in our institution). They are cited in the literature as synovial or ganglion cysts.

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Six cases of acoustic neurinomas with macrocystic components are presented. In three cases the cystic portion was within the tumor, while in the other three, the cyst was peritumoral, in the form of a cul-de-sac within the arachnoid, in other words it was not a true tumor cyst. The six tumors are from a series of 74 acoustic neurinomas treated by radiosurgery with a minimum follow-up of 18 months. In all cases, enlargement of the associated cyst was observed as early as 4 months after radiosurgery. Clinical signs and symptoms such as facial weakness, trigeminal symptoms, vertigo and dizziness and coordination disorders developed between 4 and 8 months. In three cases (two intramural cysts and one combined peri- and intramural cyst), subacute microsurgery was performed to treat the progression of neurological symptoms. One case had spontaneous rupture of an intramural cyst, one case of a peritumoral cyst, after progression showed a slow spontaneous size decrease after 2 years, and one case is still under observation. In the reported series, the dose at the tumor margin ranged between 11 and 17 Gy (mean 13.8 ± 2.5 [SD] Gy) and the maximal dose between 24 and 40 Gy (mean 30.6 ± 6.2 Gy). In view of the findings in this study, one should perhaps be cautious in advising radiosurgery for this subgroup of acoustic tumors.