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A Rare Cause Of Radiculopathy In Young Patients: A Report Of Multilevel Discal Cysts And Literature Review 2013

Category General Spine Austin C. Bourgeois, MD, BS
Kevin Liaw, MD
Scott Embry, MD
Judson Gash, MD
Purpose Magnetic Resonance Imaging (MRI) plays a prominent role in the imaging of low back pain, providing high yield in identifying space-occupying lesions attributable to focal neurological deficit.  Extradural cysts are such lesions that are prevalent and readily identified by MRI.  Their potential etiologies of include: synovial cysts, cysts of the ligamentum flavum, epidural extension of interspinous bursitis, arachnoid cysts, perineural cyst, dermoid cysts, and discal cysts.  Discal cysts are among the most rare of these entities, having less than 100 reported cases. They are usually solitary in nature, most prevalent in young males, and do not always associate with concomitant same-level disc pathology.  At least one case report describes the presence of two synchronous discal cysts (6). We report a case of a single male adult presenting with three synchronous discal cysts, providing insight into the evolutionary process of their development. A focused literature review and discussion of current diagnostic criteria, pathogenesis, and treatment will be incorporated into the discussion. Materials & Methods Following IRB approval, a retrospective chart review was performed of a recent case of three synchronous discal cysts in a young male.  Pertinent imaging findings, clinical features, and followup were included.  Literature review was performed in pubmed using the criteria "discal cyst", "disc cyst" and "extradural cyst".  Pertinent case reports and review articles were included.  Results A 22 year-old male was referred to neurology clinic with progressively worsening low back pain that began 5 weeks prior. Routine non-contrast MRI of the lumbar spine demonstrated a large central disc extrusion at L3-L4.  Intimately associated with the dorsal aspect of the extruded disc material a 7 x 12 mm ovoid lesion demonstrated high T2 and low T1 signal intensity.  Smaller cystic lesions were also present at L5-S1 and L4-L5.

  Given their size and signal characteristics, these were most compatible with discal cysts. Discal cysts, initially referred to as “disc cysts”, were first described in the English literature in 1999 (5).  Two years prior to this, in 1997, the initial description of an extradural cyst communicating with an adjacent disc was described in Japaneese.  Discal cysts are rare entities, having fewer than 100 reported cases since their discovery. They are defined as extradural cystic structures possessing intimate communication with the margin of the adjacent intervertebral disc.  Aside from their ventral anatomic location, certain associated MRI and clinical findings account for accurate diagnosis of discal cyst with relatively high specificity. They are most prevalent in young adult males, generally in the late third or early fourth decade; an age in which other advanced degenerative phenomena such as synovial cysts are uncommon. Presence of an intimate or pedicled attachment to the adjacent disc and absence of communication with adjacent facet also aids diagnosis. If discal origen is uncertain, discography has demonstrated communication between the discal cysts and discs (5).  Many discal cysts have been associated with same-level disc herniations, including the earliest reports.  However, since this time they have been described in the absence of significant same-level degenerative disc disease (1).  They may present clinically with generalized lower back pain, unilateral nerve root symptoms, bilateral radiculopathy, and neurogenic claudication. Discal cysts occur almost exclusively at one level. Our case is a unique presentation of three syncronous discal cysts, demonstrating different stages in their evolution.  Our patient presented with symptomatic radicular pain, likely as a result of moderate to severe central canal stenosis and nerve root effacement produced by the 12mm discal cyst at L3-L4.  Additionally, a small developing cyst appears at the L4-L5 level, and intermediate size cyst is present at L5-S1. A number of potential mechanisms of discal cyst pathogenesis have been proposed. The two most common of these are trauma-induced cyst formation, and cystic discal degeneration (5).  The trauma-induced theory proposes that a herniated disc ruptures a fragile epidural vein either at the time or after time of disc herniation.  The resultant small subsequent epidural hematoma is then resorbed, forming a small cyst (1).  This theory is supported by the serosanginous appearance of these cysts upon surgical examination (6).  However, lack of hemosiderin in the disk walls upon microscopic examination argues against this mechanism.  The alternative hypothesis suggests that discal cysts are a result of disc degeneration and remodeling, in a similar fashion to meniscal cysts.    Kono et al propose this method, hypothesizing that a small pseudomembrane forms around the degenerated disc material and fluid, leading to the formation of a cyst.  This is supported by the histologic findings of one surgically resected discal cyst membrane, which were compatible with a pseudomembrane (5). Conclusion Discal cysts are a rare cause of low back pain and radiculopathy in young patients.   They should be considered in the differential diagnosis of a patient with a cystic extradural mass.  MRI has proven accuracy in making this diagnosis.  The pathogenesis and treatment of discal cysts remains controversial, limited by low case volume experience.  References 1. Chiba K, Toyama Y, Matsumoto M, Maruiwa H, Watanabe M, Nishizawa T. “Intraspinal cyst communicating with the intervertebral disc in the lumbar spine: discal cyst.” Spine. 2001 Oct 1;26(19):2112-8. 2. Hyung-Jun K, Dae-Yong K, et al.  “Lumbar discal cyst causing bilateral radiculopathy.” Surg Neurol Int. 2011 Feb 23;2:21. 3. Khalatbari MR, Moharamzad Y.  “Discal Cyst in Pediatric Patients: Case Report and Review of the Literature.”  Neuropediatrics. 2012 Aug 31. 4. Koga H, Yone K, Yamamoto T, Komiya S. “Percutaneous CT-guided puncture and steroid injection for the treatment of lumbar discal cyst: a case report.” Spine 2003 Jun 1;28(11):E212-6. 5. Kono K, Nakamura H, Inoue Y, et al. “Intraspinal extradural cysts communicating with adjacent herniated disks: imaging characteristics and possible pathogenesis.” Am J Neuroradiol 1999;20:1373–7. 6. Lame A, Kaloshi G, Xhumari A, Vreto G, Petrela M. “Insights on the natural history and pathogenesis of multilevel discal cysts.” J Clin Neurosci. 2012 Apr;19(4):617-9. 7. Prasad G, Kabir SM, Saifuddin A, Casey AT. “Spontaneous resolution of discal cyst around L5 nerve root: case report and review of literature.” Br J Neurosurg. 2011 Dec;25(6):761-3. Epub 2011 Apr 18. Review. 8. Takeshima Y, Takahashi T, et al.  “Lumbar discal cyst with spontaneous regression and subsequent occurrence of lumbar disc herniation.”  Neurol Med Chir (Tokyo). 2011;51(11):809-11.