Diagnosis and Safe Excision of Lumbar Synovial Cysts and Accompanying Pathology: A Perspective
Background:Lumbar synovial cysts are often not sufficiently diagnosed prior to spine surgery. Utilizing both MR and CT studies is critical for recognizing the full extent/severity of these lesions.
Methods:In patients with chronic, acute, or subacute lumbar disease, obtaining both MR and CT studies is critical to correctly diagnose; disc disease, hypertrophy/ossification of the yellow ligament (OYL), stenosis, with/without degenerative spondylolisthesis, and/or synovial cysts (SC).
Results:MR T2 weighted images directly demonstrate hyperintensity within a SC. They initially cause lateral recess/caudad nerve root and/foraminal compromise, with larger extrusions causing significant lateral thecal sac, and far lateral/superior cephalad root compromise. CT 2 mm cuts often better demonstrate mid-vertebral level compression of cephalad nerve roots with/without SC calcification, along with the extent of mid-vertebral stenosis, hypertrophy/OYL, and DS. When CT studies directly document SC calcification, it alerts the surgeon to the increased potential risk of creating a cerebrospinal fluid fistula with full SC excision, and should prompt the adoption of alternative measures such as decompression/partial removal. Most critically, surgery for synovial cysts often warrants a 2-level laminectomy for fuller visualization of the cephalad and caudad nerve roots, and clearer differentiation of neural tissues from the large fibrotic SC capsule, to effect safer removal.
Conclusions:Preoperatively, establishing the full cephalad and cauda extent of lumbar synovial cysts with both MR and CT studies is critical. Anticipation and better visualization of the foraminal/far lateral and superior extent of these lesions often warrants more extensive multilevel laminectomies for thecal sac and both cephalad and caudad root decompression.
Both MR and CT studies are essential to preoperatively document the full extent of lumbar stenosis, hypertrophy/ossification of the yellow ligament (OYL), with/without degenerative spondylolisthesis (DS), and synovial Cysts (SC) [Tables 1 and 2; Figures 1-16].[1-15] The smaller, more typical unilateral SC occupies not only the lateral recess where they compress the caudad nerve root, but extend significantly foraminally, far laterally, and often superiorly to the mid-pedicle level where they impinge on the ipsilateral cephalad nerve root. Due to double nerve root compression (e.g. at the L4-L5 level, there is compression of the cephalad L4 and caudad L5 nerve roots), two-level lumbar laminectomies are often warranted to adequately/more safely excise SC. Larger/massive SC may occupy the majority/ entire spinal canal, resulting in not only nerve root, but also severe cauda equina compression. SC occurring alone or in combination with DS, may be managed without fusions in many patients, particularly older individuals with multiple significant comorbidities. However, for those with evidence of instability, noninstrumented vs. instrumented posterolateral fusions (PLF) vs. rarely, interbody fusions (e.g. transforaminal lumbar interbody fusions (TLIF) particularly for spondylolisthesis/lysis or full unilateral facetectomies).
Anatomy of Synovial Cysts and Radiological Appearance on MR
Pathoanatomically, synovial cysts are comprised of cystic dilatations of synovial sheaths that have directly extruded from the overlying facet joints into the spinal canal due to disruption of the facet joint capsule [Table 1]. On T2 weighted MR images, SC frequently demonstrate a hypointense outer perimeter indicative of an enlarged/hypertrophied, and/ or ossified/calcified multi-layered fibrinous capsule. The centers are inhomogeneously hyperintense reflecting the variegated soft synovial tissue intermixed with hemorrhage, and/or thick crank case fluid (e.g. rarely clear) [Table 1].[2,5]
Radiological Diagnosis of Synovial Cysts with MR
MR studies are usually the first and best examinations performed to identify lumbar synovial cyst extrusions in conjunction with lumbar stenosis, OYL, with/without DS (e.g. some cite a 40% incidence of DS with SC) [Figures 1,3,5,6,9,10 and 12] [Tables 1 and 2].[1,2,5,8,10,12,15] SC occur typically at L4-L5, followed by the L5-S1, L3-L4, and L2-L3 levels. Lateral/foraminal/far lateral SC contribute to ipsilateral thecal sac and dual cephalad/caudad root compression, while larger central/dorsolateral lesions often fill the spinal canal resulting in cauda equina syndromes.
Limitations of MR
MR axial 5 mm thick sections are focused at the disc space levels. Typically, one images is taken above, another at, and the final section just below the interspace. A limitation of axial MR studies is that they may mis/underrepresent mid-level vertebral pathology [Figures 1,5,10 and 12]. Here, sagittal/parasagittal 5 mm MR images may detect/document the missed mid-level disease [Figures 3,6 and 9].
Utility of CT Examinations in Diagnosing Lumbar Stenosis, OYL, DS, and SC
However, the non-contrast CT 2 mm axial and sagittal scans may better demonstrate mid-level vertebral disease along with stenosis, OYL, DS, spondylolisthesis/lysis, and SC, especially when considering surgery [Tables 1 and 2] [Figures 4,7,8,11,13 and 16].[1,2,5,8,10,12,15] Further, CT studies directly show ossification/calcification of SC capsules, warning of probable significant dural adherence, and prompting surgeons to consider decompression rather than full excision of SC to avoid intraoperative dural tears.
Case: When MR/CT Examinations are Interpreted as Disc, Missing Synovial Cyst
A 77-year-old female presented with several weeks of increasing left lower extremity neurogenic claudication/ radiculopathy accompanied by proximal left leg weakness (2/5), and numbness (pin loss L2-L3 distributions) [Table 2]. The preoperative MR and CT studies both “showed” L2-S1 lumbar stenosis, and a “typical” large left L2- L3 herniated disc with inferior migration to the mid-pedicle level. At surgery, the “disc” proved be a massive, extruded left L2-L3 synovial cyst. Following the L2-S1 laminectomy, no fusion was performed as there was no documented instability. Postoperatively, the patient was neurologically intact, and remained so two years later.
Pain Management (PM) Specialists’ Fail to Manage Lumbar Synovial Cysts
The 2012, Epstein and Baisden reviewed the SC literature; it showed 50-100% failure rates for PM attempts at synovial cyst “rupture/aspiration” under fluoroscopic/ CT-guidance while performing ESI (e.g. ESI with no documented long-term efficacy) [Table 1]. The PM who perform these procedures, typically including radiologists, physiatrists, and anesthesiologists, are not trained in both how to perform a neurological exam (except physiatrists), and adequately read/interpret MR/CT studies (except radiologists).[2,5] PM typically perform ESI/SC “aspiration/ rupture” attempts x 3 over 3 months, thus often critically delaying necessary spine surgery. Further, they also subject patients to dural tears, contributing to the risks of; adhesive arachnoiditis, infections, spinal headaches, intracranial hypotension, and others. Alternatively, the surgical resection of SC is highly effective in resolving back (91.6- 92.5%), and radicular pain (91.1-91.9%).
Case; PM Fail to “Rupture/Aspirate” Synovial Cyst Critically Delaying Surgery
PM followed an elderly male (e.g. >75) for over 6 months with progressive low back pain, neurogenic claudication, and radiculopathy [Table 2]. At 3 months, PM obtained an MR showing a massive L3-L4 synovial cyst with severe stenosis at L3-L4 and DS, and moderate L2-L3 stenosis. Despite continued clinical worsening, PM chose to perform 3 ESI with 3 failed attempts at SC “rupture/aspiration” over these final 3 months [Table 2]. When ultimately seen by neurosurgery, the patient had a cauda equina syndrome with repeat MR and a new CT study confirming the prior findings without a documented decrease in the size of the SC. Following a L2-L4 laminectomy, the patient fully recovered without further sequelae.
More Extensive “Open” Surgery for Safe Synovial Cyst Excision
A 2-level decompression simultaneously provides safe excision of SC, along with decompression of bilateral stenosis/ OYL with/without DS. This is typically warranted due to SC’ foraminal, far lateral, and superior extension [Tables 1 and 2].[1-15] The decompression, therefore, initiated at the superior level, allows for full visualization/decompression of the cephalad nerve root, while the inferior extension of the laminectomy facilitates decompression of the lateral thecal sac and inferiorly exiting nerve root.
Undercutting Laminectomy/Decompression of Stenosis/ OYL with/without DS/SC
Using an angled Kerrison rongeur, performing an undercutting laminectomy for SC/stenosis/OYL/DS decompression/excision involves working under an operating microscope from the opposite side of the table; further the patient is rotated/angled away from the surgeon. This technique largely provides adequate exposure while facilitating preservation of the overlying laminae/facets, use; maintaining stability, and averting fusion. It is essential to attain sufficient exposure to avoid the minimally invasive (MI) (e.g. including TLIF) increased complications that too often include; inadvertent neural/dural injury, and incomplete cyst removal.
Documentation of Location/Level of Synovial Cyst Removal with 2 X-rays
When opening at the level of a SC, the lesion may not be readily apparent. It is imperative to obtain two intraoperative radiographs to confirm the correct level; first, a cross table lateral X-ray with a clamp on the correct interspinous ligament, and second, placing a Penfield elevator in the correct disc interspace (e.g. not just in the canal). This is how to both confirm the level of the SC extrusion, as well as to avoid wrong-level surgery.
Surgery for Multilevel Stenosis/OYL, Synovial Cysts (SC), and a Foraminal (FOR)/Far Lateral Disc (FLD)
A patient (2018) presented with L2-L5 stenosis/OYL, a left L3-L4 foraminal (FOR)/far lateral disc (FLD), and bilateral L3-L4/L4-L5 synovial cysts [Table 2]. Utilizing the operating microscope, and performing L2-L5 laminectomies with medial facetectomy/foraminotomy, and undercutting the laminae/facet joints, avoided the need for fusion.
Fusion vs. No Fusion for Lumbar Synovial Cysts with Other Pathology
2004: Recommended Possible Fusion for SC with Lumbar Stenosis/OYL with/without DS
In a 2004 study, Epstein evaluated the outcomes/ frequencies of instability 2 years after multilevel laminectomies for stenosis/OYL (average 3.8 levels: 45 patients) with SC vs. multilevel laminectomies for stenosis/OYL (average 3.5 levels: 35 patients) with synovial cysts (SC), and degenerative spondylolisthesis (DS) [Table 1]. Increased olisthy (to Grade I) was seen postoperatively in 5 of 45 of the former no-DS patients, while Grade I olisthy progressed to Grade II olisthy for 11 of 35 of those with preoperative DS. Interestingly, both groups showed nearly comparable moderate postoperative improvement (e.g. good/excellent results (58% and 63% using Odom’s Criteria), and improvement in SF-36 scores (e.g. Physical Function Scale +44 and +38 points respectively). The conclusion was; “As synovial cysts reflect disruption of the facet joint and some degree of instability, primary fusion should be considered to improve operative results for patients in both categories.”
2017: No Fusion Typically Required for Laminectomy Stenosis/OYL with/without SC/DS
In 2017, Epstein documented no need for fusion following 2-3 level (58 patients) vs. 4-6 level (79 patients) lumbar laminectomies for spinal stenosis/OYL with/without SC, and DS. [Table 2]. For those undergoing 2-3 level laminectomies, all 58 had stenosis/OYL, while 48 additionally had herniated discs, 20 (34.4%) additonally had synovial cysts, and one had DS. For the 79 patients having 4-6 level laminectomies, all 79 had stenosis/OYL, 45 (56.9%) additonally had synovial cysts, 39 had lumbar discs, and 26 had DS. Despite 26 of the latter 79 patients undergoing 4-6 level laminotomies with preoperative DS, none developed postoperative instability requiring fusion [Table 2]. This represented a significant change in opinion, regarding no necessity for fusion, compared to the 2004 study.
Tisseel: Promotes Hemostasis Following Lumbar Laminectomies
Tisseel (Baxter International Inc., Westlake Village, CA, USA), a fibrin sealant, was also routinely used to minimize postoperative bleeding, facilitate hemostasis following the 2-3 (58 patients) vs. 4-6 (79 patients) level lumbar laminectomies for stenosis/OYL with/without SC, and DS [Table 2]. For both procedures, the postoperative drainage was reduced. For the 2-3 level procedures, the average drainage was 87.26 cc, and 59.62 cc on postoperative days 1 and 2 respectively, allowing for routine discharged. For those undergoing 4-6 level laminectomies, average drainage was 156.63 cc.(79 patients), 115.8 cc. (79 patients), 85.7 cc (44 patients), and 93.6 cc (6 patients) respectively on postoperative days 1-4; discharges followed at postoperative day 2 (29 patients), day 3 (44 patients), and day 4 (6 patients) Further, Tisseel was used to treat 3 dural tears (DT) attributed to calcified synovial cysts, and one DT due to scar associated with a recurrent disc out of the box 79 patients undergoig 4-6 level decompressions.
Noninstrumented PLF for Laminectomy with Stenosis/ OYL with/without SC/DS Using Different Bone Graft Expanders
Non-Instrumented PLF Rates Using Vitoss
Select patients undergoing decompressive lumbar laminectomies for stenosis/OYL, foraminal/far lateral discs, synovial cysts, and DS requiring full facetectomy with major comorbidities may warrant noninstrumented posterolateral fusions (PLF) [Tables 1 and 2].[4,8,9] In 2008, in 60 patients averaging over 70 years of age underwent average 5.4 level lumbar laminectomies and 1-2 level noninstrumented PLF; This included 48 DS, 10 degenerative scoliosis, 8 patients with synovial cysts, and 2 with spondylolysis [Table 1]. The fusion mass consisted of lamina autograft, Vitoss/B-TCP (Orthovita, Malvern, PA, USA), and bone marrow aspirate (BMA). The fusion rate was 85% based on dynamic X-rays/ CT studies obtained up to 2 years postoperatively; only 1 patient of the 15% with pseudarthrosis required secondary fusion. He was a mid-fifties vasculopathy who had to immediately go back on Aspirin therapy.
In a second study in 2016, 336 patients underwent multilevel laminectomies with noninstrumented multilevel fusions using Vitoss/B-TCP/lamina autograft/BMA [Table 1]. Patients averaged 66.5 years of age, and had average 4.7 level lumbar laminectomies, and 1.4 level noninstrumented fusions addressing; stenosis/OYL (336), DS (Grade I (195 patients), Grade II spondylolisthesis (67 patients), disc herniations (154 patients), and/or synovial cysts (66 patients). Over the average follow-up of 7.1-years, only 9 (2.7%) patients required secondary surgery an average of 6.3 years postoperatively; 7 developed Grade I DS, one progressed to a Grade II DS, 2 to new disc herniations, and/or 1 a synovial cyst.
Noninstrumented Fusion Rates for Vitoss vs. Nanoss
In 2015, Epstein compared the relative efficacy of Vitoss (213 patients) vs. Nanoss (45 patients; Regeneration Technologies Corporation: RTI, Alachua, FL, USA) using comparable noninstrumented PLF techniques [Table 1]. The average times/rates for fusion based on dynamic X-rays/2- 3D-CT studies were nearly comparable; Vitoss (5.3 months; 98.6%) vs. Nanoss (4.8 months: 100%), with pseudarthroses respectively occurring in 3 (1.4%) vs. 0 patients.
Noninstrumented Fusion Using Nanoss Alone
Subsequently, Epstein (2017) assessed 59 patients undergoing average 4.0 level laminectomies and average 1.2 level noninstrumented fusions for stenosis/OYL, DS (51 patients), synovial cysts (32 patients), and other pathology using Nanoss (RTI Surgical Alachua, FL, and USA) with lamina autograft/BMA [Table 2]. Postoperative dynamic X-rays and CT studies documented a 97% fusion rate occurring at an average of 4.9 mos. postoperatively. Notably, the 2 (3%) patients with pseudarthrosis had severe osteoporosis, were morbidly obese, and were smokers; neither, nevertheless, was sufficiently symptomatic to require additional surgery.
Frequency of Dural Tears (DT) with Lumbar Synovial Cyst Surgery
The presence of synovial cysts increases the risk of intraoperative dural tears (DT) (range 3-27%) during multilevel lumbar laminectomies with/without noninstrumented vs. instrumented lumbar fusions [Table 1].[3,7] In a 2007 retrospective analysis of 110 patients undergoing multilevel laminectomies with noninstrumented PLF, Epstein identified DT in 10 of the 110 patients [Table 1]. These patients averaged 74 years of age (e.g. vs. 69 seen for those without DT), and also correlated with slightly more extensive laminectomies (5.5 with DT vs. 5.0 without DT), and noninstrumented PLF (1.8 vs. 1.6 levels). Additionally, 3 factors positively correlated with DT; 10 DT with severe OYL, 5 of 10 patients with synovial cysts (e.g. vs. 8 synovial cysts out of 100 without DT), and 2 with prior operative scar (e.g. vs. 10 of 100 patients with scar but without DT). Next, in 2015, Epstein evaluated the incidence of DT for 336 patients undergoing average 4.7 level laminectomies, and 1.4 level noninstrumented PLF [Table 2]. DT were attributed to (in descending order); preoperative epidural spinal injections (ESI) (7 patients), synovial cysts with marked dural adhesions (6 patients), severe OYL extending through the dura (5 patients), postoperative scar (3 patients), and intradural tumors (3 patients). The overall frequency of DT was 24 (7.14%) out of 336 patients, but this number was readily reduced to 4.2% by eliminating preoperative ESI, and intradural tumors.
Recommended Repair Techniques for DT
Recommended repair techniques for DT include using 7-0 Gore-Tex (Newark, Delaware, USA) sutures (e.g. where the needle is smaller than the suture itself, thus filling the needle holes), micro-dural staples (1.4 mm), muscle patch/ bovine pericardial grafts, application of Duragen (Integra LifeSciences, Hawthorne, NY, USA), and use of a fibrin sealant (e.g. safely used Tisseel; Baxter International Inc., Westlake Village, CA, USA).
Intraoperative Neural Monitoring; Critical Adjunct to Lumbar Surgery
Extremely useful in performing multilevel laminectomies with/without non instrumented fusions is intraoperative neural monitoring. It typically consists of electromyography (EMG: some also including sphincteric monitoring), and somatosensory evoked potential monitoring (SEP); the EMG will signal root and/or sphincteri compromise, while SEP may indicate significant thecal sac/cauda equina compression. Anesthesia’s utilization of TIVA (total intravenous anesthesia) best protects the quality of these continuous EMG/SEP recordings [Tables 1 and 2].[1,2,4,6,8,9,10]
When to Say No to Surgery Due to Major Comorbidities
Not all patients with significant MR/CT documented spinal stenosis, OYL with/without synovial cysts and/or DS are appropriate surgical candidates. Major comorbidities must be carefully taken into consideration, as the risks of surgery may outweigh the benefits. The following case report illustrates this point. A 65-year-old male presented with 6 months of 2-block neurogenic claudication, but a normal neurological exam [Table 2]. MR/CT studies documented multilevel L2-S1 stenosis/OYL, Grade I L4-L5 DS, and bilateral multilevel L3-L4, and L4-L5 synovial cysts. However, he had required over 5 stents placed within the last five years, and 2 years ago, underwent placement of a bovine aortic valve, and left ventricular wall aneurysmal repair; he still required full-dose ASA (325 mg/day) and Clopidogrel 75 mg po bid therapy. Due to these multiple comorbidities and the normal physical exam, the patient was referred for conservative management (e.g. exclusive of ESI or other invasive procedures).
Lumbar synovial cysts should be more fully diagnosed preoperatively utilizing both MR and CT to demonstrate foraminal/far lateral, and superior compression of the cephalad, cauda nerve roots, and lateral thecal sac [Tables 1 and 2]. Surgery for SC with accompanying stenosis/ OYL with/without DS, typically requires 2 or more-level decompressions, avoiding the higher risks of neural/ dural injury seen with inadequate exposures provided by minimally invasive approaches.[1-15]
Declaration of patient consentNot required as there are no patients in this study.
Financial support and sponsorshipNil.
Conflicts of interestThere are no conflicts of interest.
- Spine Iphila Pa 1976). 2004;1:29(9):1049-55Lumbar laminectomy for the resection of synovial cysts and coexisting lumbar spinal stenosis or degenerative spondylolisthesis: an outcome study.
- [Google Scholar]discussion 1056
- J Spinal Disord Tech. 2004;17(4):321-5Lumbar synovial cysts: a review of diagnosis, surgical management, and outcome assessment.
- [Google Scholar]
- J Spinal Disord Tech. 2007;20(5):380-6The frequency and etiology of intraoperative dural tears in 110 predominantly geriatric patients undergoing multilevel laminectomy with noninstrumented fusions.
- [Google Scholar]
- Spine J. 2008;8(6):882-7An analysis of noninstrumented posterolateral lumbar fusions performed in predominantly geriatric patients using lamina autograft and beta tricalcium phosphate.
- [Google Scholar]
- Surg Neurol Int. 2012;3:S157-66The diagnosis and management of synovial cysts: Efficacy of surgery versus cyst aspiration.
- [Google Scholar]
- Surg Neurol Int. 2015;6:S318-22Preliminary study showing safety/efficacy of nanoss bioactive versus vitoss as bone graft expanders for lumbar noninstrumented fusions.
- [Google Scholar]
- Surg Neurol Int. 2015;6:S463-8Incidence and management of cerebrospinal fluid fistulas in 336 multilevel laminectomies with noninstrumented fusions.
- [Google Scholar]
- Surg Neurol Int. 2016;7:S331-6Low reoperation rate following 336 multilevel lumbar laminectomies with noninstrumented fusions.
- [Google Scholar]
- Surg Neurol Int. 2017;8:153High lumbar noninstrumented fusion rates using lamina autograft and Nanoss/bone marrow aspirate.
- [Google Scholar]
- Surg Neurol Int. 2017;8:246Nursing review of diagnosis and treatment of lumbar degenerative spondylolisthesis.
- [Google Scholar]
- Surg Neurol Int. 2017;8:299Tisseel’s impact on hemostasis for 2-3 and 4-6-level lumbar laminectomies.
- [Google Scholar]
- Surg Neurol Int. 2018;9:56Spinal case of the month with short perspective: How would you treat this L3-L4 synovial cyst?
- [Google Scholar]
- Surg Neurol Int. 2018;9:87Case presentation and short perspective on management of foraminal/far lateral discs and stenosis.
- [Google Scholar]
- Surg Neurol Int. 2019;10:44Avoiding inappropriate spine surgery in a patient with major cardiac comorbidities.
- [Google Scholar]
- Surg Neurol Int. 2019;10:168Case of the Week: Preoperative MR/CT Diagnosis of Left L2-L3 Disc Surgically Documented As Massive Synovial Cyst.
- [Google Scholar]
- Anatomy of Synovial Cysts and Radiological Appearance on MR
- Radiological Diagnosis of Synovial Cysts with MR
- Utility of CT Examinations in Diagnosing Lumbar Stenosis, OYL, DS, and SC
- Case: When MR/CT Examinations are Interpreted as Disc, Missing Synovial Cyst
- Pain Management (PM) Specialists’ Fail to Manage Lumbar Synovial Cysts
- Case; PM Fail to “Rupture/Aspirate” Synovial Cyst Critically Delaying Surgery
- More Extensive “Open” Surgery for Safe Synovial Cyst Excision
- Surgery for Multilevel Stenosis/OYL, Synovial Cysts (SC), and a Foraminal (FOR)/Far Lateral Disc (FLD)
- Fusion vs. No Fusion for Lumbar Synovial Cysts with Other Pathology
- Tisseel: Promotes Hemostasis Following Lumbar Laminectomies
- Noninstrumented PLF for Laminectomy with Stenosis/ OYL with/without SC/DS Using Different Bone Graft Expanders
- Frequency of Dural Tears (DT) with Lumbar Synovial Cyst Surgery
- Intraoperative Neural Monitoring; Critical Adjunct to Lumbar Surgery
- When to Say No to Surgery Due to Major Comorbidities