The Retrodural Space of Okada

Transcription

1 Musculoskeletal Imaging Pictorial Essay Murthy et al. Imaging of Retrodural Space of Okada Musculoskeletal Imaging Pictorial Essay Downloaded from by on 11/19/17 from IP address opyright RRS. For personal use only; all rights reserved Naveen S. Murthy 1 Timothy P. Maus 1 harles prill 2 Murthy NS, Maus TP, prill Keywords: contralateral, facet joint, infection, injection, retrodural DOI: /JR Received September 8, 2010; accepted after revision November 5, Department of Radiology, Mayo linic Rochester, 200 First St SW, harlton 2-290, Rochester, MN ddress correspondence to N. S. Murthy (murthy.naveen@mayo.edu). 2 Departments of Radiology and Medicine, Louisiana State University Health Sciences enter, New Orleans, L. WE This is a Web exclusive article. JR 2011; 196:W784 W X/11/1966 W784 merican Roentgen Ray Society The Retrodural Space of Okada OJETIVE. The retrodural space of Okada is a potential space that can act as a conduit for the spread of inflammatory or infectious processes, connecting ipsilateral adjacent facet joints, contralateral adjacent facet joints, adjacent neural foramen, paraspinal musculature, and spinous process adventitial bursa (i.e., aastrup disease). ONLUSION. wareness of these potential retrodural communications during diagnostic imaging interpretation and interventional spine injection procedures can play an important role in patient care and management. communication pathway between single-level bilateral cervical facet joints was first described by Dr. Kikuzo Okada in 1981 [1]. He found that 80% of the studied cervical facet joints could communicate with the interlaminar region, interspinous region, and contralateral facet joints via an extradural space that lies dorsal to the ligamentum flavum (Fig. 1). This retrodural and retroligamentous communication described by Dr. Okada is illustrated in Figure 2, wherein a therapeutic right 5 6 facet joint injection was performed for mechanical neck pain. ontrast agent opacification is seen to fill the intended facet joint but then spread across the midline to the contralateral facet joint. Subsequent reports have described communications of lumbar spondylolytic defects with adjacent and contralateral facet joints [2 7]. The pars interarticularis forms the only boundary between the inferior articular recess and the superior articular recess of adjacent ipsilateral facet joints [5]. Therefore, when there is a break in the pars interarticularis, a communication can form between the inferior and superior articular recesses of the two adjacent ipsilateral facet joints. In addition to this communication, the ligamentum flavum is absent at the level of the pars interarticularis, which can permit transverse extradural, or retrodural and retroligamentous, communication to the contralateral facet joint. Figure 3 illustrates this communication, whereby an attempted transforaminal epidural injection was performed for diagnostic and potential therapeutic purposes. Rather than filling the epidural space, contrast agent was seen to flow into the adjacent facet joint and pars interarticularis defect, then across the midline to the contralateral pars interarticularis defect and facet joint. There have been additional reports of retrodural and retroligamentous communications with adjacent ipsilateral and contralateral facet joints, with and without spondylolysis, during arthrography [8, 9]. Therapeutic facet joint injections shown in Figures 4 and 5 illustrate the spread of contrast agent from the targeted facet joint across the retrodural and retroligamentous space into the contralateral facet joint. Four different configurations of the ventral aspect of lumbar facet joints have been described [10]. In one of these (type 2), the ventral joint capsule extends under or dorsal to the ligamentum flavum toward the midline. This finding is likely related to the observations made by Dr. Okada [1]. The inferior articular recess normally has an opening along its inferomedial aspect that communicates with the extracapsular fat that is bounded by the attachments of the paraspinal musculature [5]. recent report described septic arthritis of bilateral lumbar facet joints not associated with spondylolysis [11]. The authors reported contiguous extension of the joint infection into the paraspinal musculature and soft tissues without involvement of the vertebral body, disk, or epidural space. These findings would support the anatomic communication between the inferomedial aspect of the inferior articular recess with the extracapsular fat bounded by the paraspi- W784 JR:196, June 2011

2 Imaging of Retrodural Space of Okada Downloaded from by on 11/19/17 from IP address opyright RRS. For personal use only; all rights reserved nous musculature. Figure 5 depicts this extracapsular extension during a therapeutic facet joint injection performed for mechanical back pain. It can be postulated that the inflammatory process from within the joint may spread through the retrodural space transversely to involve the contralateral facet joint. The superior articular recess is entirely intracapsular; however, there have been reports of a communication with the neural foramen and an opening along the lateral aspect of the superior articular recess [12]. Figure 6 exemplifies this reported finding. facet joint injection was performed in hopes of addressing an intraspinal synovial cyst arising from the targeted facet. During the injection, contrast agent was seen to opacify not only the retrodural and retroligamentous space but also the adjacent ipsilateral epidural space within the neural foramen. dditional communications with the retrodural space have been described in patients with advanced degenerative changes or adventitial bursa formation between the spinous processes (i.e., aastrup disease) and the adjacent facet joints [13]. These findings also lend support to an extensive potential retrodural space seen with inflammatory or infectious processes. s seen in Figure 6, the injected contrast agent also communicates with the adventitial bursa between the spinous processes. The MRI scans in Figure 7 reveal contiguous T2 signal hyperintensity within the same level facet joints, the retrodural space, and the adventitial bursa between the spinous processes in a patient with a presumed inflammatory right L5 radiculopathy. In another case, an interlaminar epidural injection performed in a patient with pseudoclaudication inadvertently accessed the retrodural and retroligamentous space because of a premature loss of resistance (Fig. 8). ontrast agent opacification revealed the extradural position while communicating with the adjacent facet joint. Yet another case (Fig. 9) depicts a communication between the facet joint and the adventitial bursa between the spinous processes during a therapeutic facet joint injection. wareness of these potential retrodural communications during diagnostic imaging interpretation and interventional spine injection procedures can play an important role in patient care and management. These communications may be conduits for infectious or inflammatory processes, as discussed previously in the article, but may also depict intended or unintended avenues of contrast agent spread in cases where a steroid injectate will be used for diagnostic or therapeutic purposes. References 1. Okada K. Studies on the cervical facet joints using arthrography of the cervical facet joint. Nippon Seikeigeka Gakkai Zasshi 1981; 55: Duprez T, Mailleux P, odart, oulier, Malghem J, Maldague. Retrodural cysts bridging a bilateral lumbar spondylolysis: a report of two symptomatic cases. J omput ssist Tomogr 1999; 23: Ghelman, Doherty JH. Demonstration of spondylolysis by arthrography of the apophyseal joint. JR 1978; 130: Maldague, Mathurin P, Malghem J. Facet joint arthrography in lumbar spondylolysis. Radiology 1981; 140: Mcormick, Taylor JR, Twomey LT. Facet joint arthrography in lumbar spondylolysis: anatomic basis for spread of contrast medium. Radiology 1989; 171: Park WM, Mcall IW, enson D, Seal PV, O rien JP. Spondylarthrography: the demonstration of spondylolysis by apophyseal joint arthrography. lin Radiol 1985; 36: Shipley J, eukes. The nature of the spondylolytic defect: demonstration of a communication synovial pseudarthrosis in the pars interarticularis. J one Joint Surg r 1998; 80: Sarazin L, hevrot, Pessis E, et al. Lumbar facet joint arthrography with the posterior approach. RadioGraphics 1999; 19: annon DT. The lumbar retroligamentous space: description and implications for the spinal injectionist. International Spinal Injection Society Newsletter 2000; 3: Xu GL, Haughton VM, arrera GF. Lumbar facet joint capsule: appearance at MR imaging and T. Radiology 1990; 177: Doita M, Nishida K, Miyamoto H, Yoshiya S, Kurosaka M, Nabeshima Y. Septic arthritis of bilateral lumbar facet joints: report of a case with MRI findings in the early stage. Spine (Phila Pa 1976) 2003; 28:E198 E Lewin T, Moffett, Viidik. The morphology of the lumbar synovial intervertebral joints. cta Morphol Neerl Scand 1962; 4: hen K, Yeh L, Resnick D, et al. Intraspinal posterior epidural cysts associated with aastrup s disease: report of 10 patients. JR 2004; 182: Fig. 1 Schematic of retrodural space of Okada. Reprinted with permission from Mayo Foundation for Medical Education and Research. ll rights reserved. JR:196, June 2011 W785

3 Murthy et al. Downloaded from by on 11/19/17 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with mechanical neck pain., Image shows 25-gauge needle appropriately placed in midportion of right 5 6 facet joint. ontrast opacification shows contrast agent flow (arrows) into facet joint and toward midline. and, ontrast agent continues past midline (arrows, ) into contralateral facet joint (white arrows, c) via retrodural space. ontrast agent is seen within lateral recess of contralateral facet joint (black arrow, c). D Fig year-old man with right leg dysesthesia of uncertain cause., Image shows 25-gauge needle (arrow) appropriately positioned in superior and ventral aspect of right L4 neural foramen for transforaminal epidural steroid injection. ilateral L5 S1 pars interarticularis defects (arrowhead) are seen., Test contrast agent injection shows opacification of superior articular recess of right L4 L5 facet joint (arrow) and of ipsilateral pars interarticularis defect (arrowhead)., ontrast agent continues to fill ipsilateral facet joint and pars interarticularis defect (white arrow), with extension into and across retrodural space to fill contralateral pars interarticularis defect and contralateral facet joint (black arrow). D F, T images obtained immediately after study confirm fluoroscopic findings. ontrast agent is seen in retrodural space (arrows, d), opacification of pars interarticularis defects is seen (arrows, e), and contrast agent is seen within bilateral facet joints (arrows, F). E F W786 JR:196, June 2011

4 Imaging of Retrodural Space of Okada Downloaded from by on 11/19/17 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with right L5 radiculopathy related to right L4 L5 facet joint intraspinal synovial cyst. T images were acquired to opacify intraspinal synovial cyst emanating from superior articular recess of right L4 L5 facet joint., Unenhanced injection image shows gas within facet joints and intraspinal synovial cyst (arrow). and, Subsequent T fluoroscopy images acquired over ensuing 5 seconds with contrast injection show contrast agent filling retrodural space (arrows, ) and subsequent contralateral facet joint (arrow, ). D E Fig year-old man with mechanical low back pain., Image shows 22-gauge needle placed in left L4 L5 facet joint., ontrast injection shows ipsilateral facet joint opacification and opacification of retrodural space (arrows)., Image shows subsequent filling of contralateral facet joint (arrow). D and E, T images confirm fluoroscopic findings. ontrast agent is seen within retrodural space (arrows, D) with eventual opacification of both facet joints (arrows, E). Note contrast agent leakage into extracapsular fat bounded by paraspinous musculature (arrowhead, E), which can explain contiguous involvement of these structures and facet joints with inflammatory or infectious processes. JR:196, June 2011 W787

5 Murthy et al. Downloaded from by on 11/19/17 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with right L5 radiculopathy related to right L4 L5 facet joint intraspinal synovial cyst., Image shows 25-gauge needle placed in right L4 L5 facet joint, with contrast agent filling facet joint and retrodural space to midline (arrows). and, T images confirm contrast agent opacification of right L4 L5 facet joint (arrow, ) and retrodural space (black arrow, ). Faint contrast opacification of ipsilateral epidural space (white arrow, ), presumably resulting from reported communication of neural foramen with lateral aspect of superior articular recess, is seen. D and E, ontrast agent eventually fills adventitial bursa (arrow, D and E) between spinous processes. Fig year-old man with right L5 radiculopathy., Image shows increased T2 signal (arrows) representing inflammatory change or fluid involving both L4 L5 facet joints and retrodural space. and, dditional abnormal T2 signal is seen extending into interspinous region (arrow, and c), representing communication to interspinous adventitial bursa. D E W788 JR:196, June 2011

6 Imaging of Retrodural Space of Okada Downloaded from by on 11/19/17 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with pseudoclaudication., Interlaminar epidural steroid injection was performed, with false loss of resistance dorsal to ligamentum flavum into retrodural space. Subsequent contrast opacification of retrodural space connecting interspinous region or adventitial bursa with adjacent facet joint occurred. ontrast agent accumulation (arrows) is seen within superior and inferior articular recesses of right facet joint., Image shows slight ventral advancement of needle, resulting in epidural opacification (arrows). Fig year-old woman with left L5 radiculopathy related to left L4 L5 facet joint intraspinal synovial cyst., Image shows 25-gauge needle placed in left L4 L5 facet joint, with contrast agent filling facet joint (arrow)., T maximum-intensity-projection image better depicts contrast agent opacification of left L4 L5 facet joint (white arrow) and retrodural space extending into adventitial bursa between spinous processes (black arrows)., T maximum-intensity-projection image in sagittal plane also depicts contrast agent within retrodural space (arrows) extending into adventitial bursa between spinous processes. JR:196, June 2011 W789