Facet cysts were first described by Kao.1 These

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1 16 Percutaneous or Endoscopic Treatment of the Facet Cysts 93 Introduction Etiopathogenesis Facet cysts were first described by Kao.1 These cysts, which mostly originate from synovial, are typically located in the posterolateral aspect of the thecal sac in lumbar vertebras. 2-7 Lumbar facet cysts are in the lower rows in the list of causes of neurogenic claudication, radiculopathy and low back pain. 8,9 There were difficulties in the diagnosis in the past years. However, with the advancement and spreading of the imaging techniques in the recent years, reaching the diagnosis have become easier and greater numbers of cases are being reported. Incidence and Demographic Characteristics Ninety-four percent of the synovial cysts located in the vertebral column are in the lumbar area, and are much rarer in the thoracic (2%) and cervical (2%) areas. 4 They are most frequently seen in the L4-L5 level and is accompanied by the degenerative arthropathy of the facet joints. 10,11 It is more frequent in the sixth decade. The average age was found as 65 in the study of Trummer and colleagues. 12 However, it has been shown in different series that it can be seen between 28 and 94 years of age. 13,14 Male/female ratio varies. Hsu et al. showed this ratio as 2:1 in their study, and Lyon et al. reported as 1:1. 5,11 It frequently causes central and/or lateral stenosis of the lateral recess. Although etiology is not exactly known, segmental hypermobility or instability are factors that are most frequently accused factors in the pathogenesis. 8 It has been shown in many postmortem studies that synovia of the facet joints brim over the joint surface and enters the flavum ligament. 13 Pathologically, it is seen that the synovial epithelium is surrounded with a cover, and this ensures the differentiation of the cystic degeneration of the flavum ligament. Synovial cysts are markedly connected to the synovial sheath or the articular capsule within the synovia-like cover, and this cover contains a xanthochromic fluid. 14,15 Clinic and Diagnosis While the diagnosis or some cases are entirely coincidental, most the cases have a symptomatic course. Cysts that grow into the epidural region compress the neural structures within the dura and cause symptoms. Severity of these symptoms is directly related with the volume and localization of the cyst. 16 The most frequent symptom is radiculopathy, which is mostly one-sided. Neurologic claudication is the second most frequent symptom. Neurologic losses, which can be sensory or motor, follow these. 11,16-18

2 94 Direct x-rays among the imaging methods has no place in the diagnosis. However, it can be helpful in the differential diagnosis of the destructive lesions including the spondylodiscitis and metastatic conditions or degenerative problems. Computerized tomography and particularly the magnetic resonance imaging (MRI) are rather valuable both in the diagnosis and planning of the treatment. MRI displays the image of the cyst and its relation with the surrounding neural structures in detail (Figure 1). Cysts is rather well-limited and gives higher signal intensities both in T1 and T2 as compared to the cerebrospinal fluid because of its protein contents. 19 Treatment a. Conservative approaches: Follow-up, bed rest, oral analgesics, physical therapy, aspiration under CT guidance and intrarticular steroid injection can be listed under this headline. Aspiration under CT guidance is one of the minimal invasive methods applied. However, However, leaving the cyst wall behind increases the risk of recurrence and recurrence is seen within one year in the majority of the cases. 20 Steroid injection within the facet joint is a method applied since the 80s. Although the results are Figure 1: T2-weighted sagittal (a) ve axial (b) magnetic resonance imaging (MRI) sections in the 55-year old female presenting with sciatica variable, it is known that it provides relief to a certain extent. 6,21 Technically, facet joint is entered under the guidance of the facet joint and under local anesthesia. Later, the misture of depot steroid and local anesthetic is injected to the joint and then diluted nonionic contrast agent is injected in the cyst to make it burst. Spreading of the contrast agent in the epidural space shows that the cyst had burst. Martha et al. succeeded in making the cyst burst in 81% of the cases that had applied this technique. However, recurrence was observed in more than one half of the patients in 80% that follow-up was possible. These patients were revised surgically later. 22 Bureau et al tried cyst rupture with percutaneous corticosteroid injection in symptomatic patients. Full regression was obtained in 50-70% of the patients in control MRI. Two or more injections were needed in more than 50% of the patients within 6 months. While excellent results were reported for 75% of the patient, no improvement was seen in 17%. 6 It has been reported that epidural steroid injection can provide relief for the short term. However, the effects for mid- and long-term are not known. 15,21 b. Surgical approaches: Synovial cysts can be treated with percutaneous aspiration or with steroid injections into the facet joint; however, surgical excision is the most definitive treatment method particularly in cases with excruciating pain or neurologic impairment. Classically, medial facetectomy with laminectomy or partial parsiyel laminectomy is a method used for complete visualization and removal of synovial cysts with severe adhesions. 17 Injuries of neural structures, CSF leakage, epidural hematomas and instability or requirement of spinal fusion in later periods can be listed among the complications of such interventions. 11 Successful results with the use of minimal invasive methods have been reported

3 Percutaneous or Endoscopic Treatment of the Facet Cysts 95 Figure 2: Determining the L4-5 level under fluoroscopy guidance and placement of the working cannula in the recent years. The surgically recognized techniques include the posterior interlaminar endoscopic technique and the MetRx tube endoscopy technique. 17,23 In both techniques, level is determined under the fluoroscopy control (Figure 2). Later, the surgical incision is by making a 2-cm longitudinal paramedian skin incision. The subcutaneous tissue and muscles are separated with blunt dissection and the lower border of the lamina adjacent to the facet joint to be approached. The endoscopic working cannula to be used is placed and the procedure is thus started. Hemi laminectomy is performed by starting from the caudal part of the lamina of cranial vertebra that form the facet joint tills the origin of the flavum ligament. Then, flavectomy is performed starting from the cranial end and advancing towards the caudal. The facet cyst appears when extending the lamiectomy towards the facet joint, and the contents of the cyst is excised together with the cyst wall (Figure 3). Figure 3: See the cystic contents in the neighborhood of the dura (a). It is seen in the control MRI at the end of the postoperative year 1 that there is no recurrence (b)

4 96 The patient can be mobilized in the postoperative day 1 without any need for a corset. 23 Discussion Synovial cysts of the vertebra are most frequently seen in the lumbar region. It is most frequently found in the L4-L5 vertebral level adjacent to the degenerative facet joint. 4 The reason for frequency in this level is that this segment is more hypermobile and the facet joint degeneration is more common in this level. It can cause radiculopathy frequently, and severe low back pain and neurogenic claudication are the symptoms seen most frequently. Conservative approaches can be tried in the first place in the treatment of these lesions. There are a few publications stating the benefits of immobilization and medical treatment; however, there is no information concerning the failure of these treatment methods. 18,24 Percutaneous cyst aspiration and steroid injections to the facet joint are other possible treatment methods. Koenigsberg reported that percutaneous aspiration of the cystic contents had provided radiologic and symptomatic improvement. However, the follow-up period is only 10 days. 20 The surgical excision of the cyst is the best treatment method. Laminectomy and medial facetectomy are most frequently used methods. Adhesion of the cyst to the dura and neural roots can increase the risk of dural tears and nerve root injuries. Instability that can develop in the vertebral column after the laminectomy can require fusion in the late period. Lyons et al. reported the complication rate as 4% in their series of 194 patients. 11 It is reported in the literature that instability develops with a rate of 9 11% and requires fusion. Minimal invasive treatment methods were started to be used frequently in the excision of the vertebral synovial cysts to prevent the possible complications and shorten the period of hospital stay. Sandhu excised 18 synovial cysts in 17 patients with minimal invasive approach using the tübüler retractor system, and reported good and excellent results with a rate of 94%. None of the cases required spinal fusion. 17 Oertel et al. reported successful results with microsurgery with a rate of 83%. 25 Deinsberber et al. reported good and excellent results in their study with minimal invasive treatment methods with a rate of 80.7% after a follow-up rate of months. Although spondylolisthesis was found in 45.4% of the patients, spinal fusion was not required perioperatively or within the follow-up period. 26 The minimal invasive approaches in the treatment of the synovial cysts in the spine significantly prevent the complications and reduce the risk of vertebral instability development after laminectomy by preventing the injuries of the paravertebral structures (ligaments and bony structures). Reducing the anesthesia period for the patients with internal problems and reducing the hospital stay and workforce loss are other advantages.

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