Surgical strategy for multiple huge spinal extradural meningeal cysts

J Neurosurg (4 Suppl Pediatrics) 107:297–302, 2007

Surgical strategy for multiple huge spinal extradural meningeal cysts Case report KAZUHIRO SAMURA, M.D.,1 TAKATO MORIOKA, M.D., PH.D.,1 YASUSHI MIYAGI, M.D., PH.D.,1,3 SHINJI NAGATA, M.D., PH.D.,1 MASAHIRO MIZOGUCHI, M.D., PH.D.,1 FUTOSHI MIHARA, M.D., PH.D.,2 AND TOMIO SASAKI, M.D., PH.D.1 Departments of 1Neurosurgery and 2Clinical Radiology, Graduate School of Medical Sciences, and 3 Division of Digital Patient, Digital Medicine Initiative, Kyushu University, Japan

PThe authors describe the case of an 8-year-old boy who developed spastic paraparesis and hypalgesia below the middle thoracic level. Magnetic resonance (MR) imaging showed huge and multiple extradural cystic lesions posterior to the spinal cord from T-5 to S-1, which were associated with severe spinal cord compression, especially at the T5–8 level. Using constructive interference in steady state (CISS) MR imaging, many septa were visible that were dividing the cysts in a tandem arrangement, and the multiple cysts were distributed far laterally, extending to the root sleeves. Three transdural communications of cerebrospinal fluid into the cysts, including one that was located ventrally, were revealed by multiangled observation using CISS MR imaging and intraoperative inspection. The huge and multiple appearances of the extradural meningeal cysts on MR images suggested various stages of growth of these cysts. As this case demonstrates, cysts of this type (huge, multiple, extradural meningeal [arachnoid] cysts) need to be completely removed during one-stage surgery. (DOI: 10.3171/PED-07/10/297) KEY WORDS • constructive interference in steady state • extradural arachnoid cyst • magnetic resonance imaging • multiple cystic lesion • pediatric neurosurgery • spinal meningeal cyst

A

N SEMC is an uncommon lesion that communicates

with the subarachnoid space through a small dural defect and expands into the extradural space with progressive spinal cord compression. It is believed that the one-way valve mechanism of CSF flow causes the arachnoid membrane to become herniated and enlarged in the extradural space.10 In this report, a very rare case of huge multiple SEMCs posterior to the spinal cord extending from T-5 to S-1 is described. Although standard treatment for a solitary SEMC is cyst removal and closure of the transdural CSF communication, surgery for multiple SEMCs is more complex. The neuroimages obtained in this case provided important clues for identifying the site of CSF communication, the mechanisms of SEMC development, and possible surgical strategies for removing the multiple SEMCs.

Abbreviations used in this paper: CISS = constructive interference in steady state; CSF = cerebrospinal fluid; MR = magnetic resonance; SEMC = spinal extradural meningeal cyst.

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Case Report Presentation and Examination. This 8-year-old boy developed progressive spastic paraparesis and hypalgesia below the middle thoracic level. On admission, his paraparesis deteriorated further and he occasionally suffered urinary incontinence. An anterior view of the spine on a plain radiograph showed a widening of the interpeduncular distance of the vertebrae from the cervical to the sacral region. A computed tomography scan demonstrated thinning of the pedicles and enlargement of the spinal canal from the thoracic to the lumbar region, which suggested slow and progressive expansion of a lesion. The MR imaging results showed huge extradural lesions posterior to the spinal cord at the T-5 to S-1 level. The lesions produced low and high signal intensities on T1- and T2-weighted MR images, respectively (Fig. 1A and B). Diffusion weighted MR imaging demonstrated homogeneous low signal intensities in the lesion, indicating a cystic lesion containing CSF. Spinal cord compression was severe, especially at the T5–8 level, 297

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FIG. 1. Magnetic resonance images demonstrating massive SEMCs compressing the thoracolumbar spinal cord in an 8-year-old boy. Sagittal images of T1-weighted (A) and T2-weighted (B) sequences show the cystic lesions forming a tandem arrangement. The arrows indicate the signal change in the spinal cord due to compression. The coronal CISS MR image (C) shows the lateral extension of meningeal cysts into the intervertebral foramen. A 3D reconstruction of the CISS MR image (D) demonstrates the spatial relationship between the multiple cysts, the dural sac, and their areas of communication (left, anterior view; right, lateral view).

where the spinal cord showed a T2 elongation on MR images (Fig. 1B). On sagittal CISS MR images, many septa were visibly dividing the lesion into multiple cysts, some of which extended far laterally into the intervertebral foramen, as noted on coronal MR images (Fig. 1C). Three-dimensional reconstruction of CISS MR images demonstrated the spatial relationship between the multiple cysts, the dural sac, and their areas of communication (Fig. 1D). Cine MR imaging failed to detect CSF flow between the subdural space and the cystic lesions; however, meticulous observation using CISS MR imaging at multiple angles revealed three sites of CSF communication with the subarachnoid space—at the T-8, L-3, and L-5 levels (Fig. 2). First Operation. The extradural cystic lesions were initially explored using laminoplastic laminotomy at T8–12, where the spinal cord compression appeared most severe on MR imaging. Under the laminae, three cysts were found embedded in the epidural fat tissues, and the cysts were squeezed and divided by the septa with fibrovascular tissues (Fig. 3A). The cysts were filled with watery, clear CSF, and were dissected from the surrounding fat tissues and excised. The cyst at the T-8 level had a pedicle, which communicated with the subarachnoid space through the dural fistula. Normal spinal cord was visible through the pedicle (Fig. 3B); the pedicle was ligated with a silk suture to close the transdural communication with the subarachnoid space 298

FIG. 2. Multiangled CISS MR images showing the transdural communications of CSF (arrows). The axial views at the T-8 (A) and L-3 (B) levels and the oblique view at the L-5 (C) level show the fistulas communicating between the cyst and the subarachnoid space.


Multiple spinal extradural meningeal cysts

FIG. 3. Intraoperative photographs (left) and accompanying illustrations (right). A: Under the T8–12 laminae, multiple cysts were embedded in a tandem arrangement (arrows). The cysts were squeezed by fibrovascular trabeculae. B: Intraoperative inspection inside the SEMCs revealed the communication with the subarachnoid space, as had been identified on CISS MR images (Fig. 2), where the spinal cord (S) and roots (R) could be seen. C: The pedicle of the L1–2 cyst was closed with a silk suture and filled with saline. The cyst had a complicated shape, as was shown in 3D reconstructed images (Fig. 1D), suggesting an extension in the direction of lower tissue resistance.

(Fig. 3C). The other two cysts were not associated with transdural CSF communication and were easily extirpated. Postoperative Course. Histological examination of the cyst wall demonstrated the presence of thick fibrocollagenous tissue. The inner wall was not covered with an arachnoid cell layer; however, arachnoid cells were embedded in the thick collagen tissues. After surgery, the patient’s paraparesis did not improve. On postoperative MR imaging (Fig. 4A), the cysts had disappeared at the T5–8 level, the extradural cavity was filled with the same signal intensity as CSF, and the spinal cord compression was slightly reduced. After 2 weeks, the extradural dead space became larger and the spinal cord compression became much more severe than before (Fig. 4B). The patient’s spastic paraparesis did not improve but gradually worsened in the third week. No constipation J. Neurosurg: Pediatrics / Volume 107 / October, 2007

was noted. Finally, the patient developed much more severe urinary incontinence and became unable to walk by himself in the fourth week after surgery; therefore, a radical emergency second surgery was required. Second Operation and Postoperative Course. During the second surgery, a double-door laminoplastic laminotomy was extended from T-4 through L-5 to explore and remove all the multiple meningeal cysts in the extradural space. The extradural space was filled with CSF, suggesting that the extradural dead space was hindered from shrinking by the residual cysts rostral and caudal to the dead space. Two separate dural fistulas and cyst pedicles were found at the L-3 and L-5 levels, as was revealed by preoperative CISS MR imaging (Fig. 2B and C). The pedicles were ligated with a silk suture and the cysts were excised. There were some 299

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FIG. 4. Postoperative T2-weighted midsagittal MR images of the SEMCs after the first (A and B) and second (C) surgeries. The image on the third postoperative day (A) showed that cyst removal had relieved spinal cord compression. Two weeks later (B), the extradural cavity had expanded in association with CSF reaccumulation, and the residual cysts had again produced a significant mass effect on the spinal cord. At the 6-month follow-up after the second surgery (total removal of the cysts; C), the mass effect of the extradural cavity on the spinal cord had completely resolved. The images from the neck (T4–7) and body (T8–S1) coils in panel C were combined to represent the same area as panels A and B.

cysts that were also filled with clear CSF, but they were not associated with either pedicle or dural fistulas. After the removal of all cysts and repair of the dural fistulas, the dura mater was lifted up to the lamina using tenting sutures to minimize the extradural dead space. The patient recovered gradually over 3 months, and MR imaging (Fig. 4C) after 1 year showed complete relief of the spinal cord compression. Discussion An SEMC is uncommon, and symptomatic cases are even more uncommon.6 These cysts occur predominantly in the thoracic spine and, to a lesser extent, in the lumbar and lumbosacral spine.3 Nabors and colleagues10 classified SEMCs as Type IA congenital spinal meningeal cysts. The SEMCs are believed to result from a dural defect or fistula due to some type of spinal dysraphism or trauma, congenital diverticulum of the dura, or herniation of the arachnoid membrane through a congenital defect in the dura.1,2,14 The pathogenesis of cyst enlargement is considered to be a one-way valve mechanism in which pulsatile CSF enters the cyst and reflux is blocked at the neck of the diverticulum.15 300

The most common symptoms of SEMCs are pain, paresthesias, intermittent claudication, and variable degrees of paraplegia. In some cases, pain and weakness in the lower extremities are specifically aggravated by a Valsalva maneuver, which increases pressure within the cyst.3,4 These symptoms are relieved by bed rest or bending forward, which is thought to decrease pressure within the cyst.16 The natural history of SEMCs is not well understood. The unique aspect of the present case is the multiplicity and size of the SEMCs. There have been only two previous case reports of multiple SEMCs,2,8 in which each SEMC protruded from a separate dural fistula. In the present case, we detected 14 cysts on preoperative CISS MR imaging. Ten meningeal cysts were recognized during surgery and three transdural CSF communications were revealed near the T-8, L-3, and L-5 root sleeves. Nakagawa and associates11 reported a case involving huge SEMCs at the T-11 to S-1 level; however, the cysts in our case were distributed from the T-5 to the S-1 level, which was a much larger area than in any previous reports. Most SEMCs have transdural communications with the subarachnoid membrane,10 and are often found in the posJ. Neurosurg: Pediatrics / Volume 107 / October, 2007

Multiple spinal extradural meningeal cysts terolateral dura around the root sleeve during surgery.2,7,10,12 Although the use of myelography or computed tomographic myelography for SEMCs can usually demonstrate the existence of transdural CSF communication,10,16 it is sometimes difficult to accurately localize the communication point with these methods—even a meticulous inspection sometimes fails to localize transdural CSF communication or dural defects in up to 30% of cysts during surgery.6,8,10,13 Therefore, the possibility cannot be excluded that some cysts are isolated and are closed spontaneously by meningeal septa in the course of their development. In this case, three sites of transdural CSF communication were detected using 3D CISS MR imaging, which has high spatial resolution and excellent contrast between CSF and solid structures.11 The sequences of CISS MR images have been described in detail in our previous reports.5,9 The ventrolateral location of transdural CSF communication (the cyst pedicle), as detected on preoperative CISS MR imaging (Fig. 2), was also observed in another case report.8 This finding suggested a rotational shift of the dural sac caused by unilateral anterior compression by the cyst around the root sleeves, because the cyst pedicles were actually found at the posterolateral surface of the dural sac during surgery, as has been widely reported.2,7,8,10,12 The oblique views from multiple angles reconstructed from CISS MR images using 3D image reconstruction software were helpful in detecting transdural communication, especially in this case involving a complex form of cyst pedicles and the rotational deformity of the dural sac (Fig. 2C). Cine MR imaging may also be useful for visualizing the pulsatile CSF flow between cysts and the subarachnoid space, through the transdural communication.4,12 In the present case, however, cine MR imaging failed to detect CSF flow below the level of spinal cord compression, probably because of severe blockage of the spinal canal. It is thus suggested that the spinal canal stenosis itself might also have worked as a valve mechanism; that is, pulsatile CSF flow entered the subarachnoid space below the level of spinal cord compression, increasing the cyst pressure and the severity of spinal cord compression, and inhibiting the transmission of CSF pulsation. This hypothesis may explain why no CSF flow was detected by cine MR imaging. The various shapes of cysts and/or septa observed on CISS MR imaging in this case (Fig. 1C and D) suggested that cyst extension occurred in the direction of lower tissue resistance. Thus, these cysts may appear at the dural fistula in the posterolateral dura near the root sleeve, extending initially to the midline and then in a rostrocaudal direction, until they collide with adjacent cysts; finally, these cysts may extend laterally into the intervertebral foramen. Fibrovascular trabeculae in the epidural fat may intercept the enlargement of meningeal cysts, leading to septum formation. This hypothesis should be verified after further experience with SEMCs. Nakagawa and coworkers11 performed neuroendoscopic surgery and found multiple septa inside a cyst. In their case, the cyst proved to be solitary, but they could not find any dural fistulas. After the first surgery, the fistula was detected on CISS MR imaging, and they had to close it during the second surgery. There has been a case report of an intradural/extradural arachnoid cyst treated by percutaneous aspiration of the cyst contents under MR imaging guidance, which proved to be successful after 1 year of follow-up;1 J. Neurosurg: Pediatrics / Volume 107 / October, 2007

however, standard treatment for a solitary SEMC is considered to be complete removal of the cyst and closure of the transdural CSF communication between the cyst and the subarachnoid space.10,13 According to a review of 10 cases of SEMCs by Hatashita et al.,6 simple closure of the dural fistula or cyst pedicle is ineffective: there was no CSF reaccumulation in the extradural space of any patient who underwent cyst removal alone without closure of the transdural CSF communication. Nine of the ten patients in that study achieved complete recovery or some neurological improvement and the other experienced no change. In contrast, Sato and associates16 reported that total resection of SEMCs is unnecessary if the posterior wall of the thecal sac has been explored and the dural fistula has been closed. Radical removal of the SEMC is accepted as a primary treatment, and simple aspiration of the cyst contents is not sufficient.2,8,13 In the present case with huge and multiple SEMCs, simple removal of only the largest cyst left an extradural dead space between the remaining cysts. This extradural dead space was soon filled with leaked CSF, grew larger, and elicited the spinal cord compression again. Nabors and colleagues10 reported a similar experience with spinal meningeal cysts, in which the insertion of a ventriculoperitoneal shunt was required for treating a recurrent cyst. Based on previous reports and this case, it appears necessary to remove all of the SEMCs and to close the dural fistulas during the initial surgery. Use of tenting sutures to lift up the dura to the vertebral arch may help to avoid CSF reaccumulation in the extradural cavity in cases of huge, multiple SEMCs. Conclusions Multiple SEMCs, as seen in this case, are extremely rare. The MR imaging appearances of the SEMCs in this case suggested various stages of SEMC development. Great care should be taken when deciding on a surgical strategy for treating multiple SEMCs. Complete removal of multiple SEMCs is recommended, because partial removal of the largest cysts may result in CSF reaccumulation in the extradural dead space, which in turn may elicit spinal cord compression. References 1. Bellavia R, King JT Jr, Naheedy MH, Lewin JS: Percutaneous aspiration of an intradural/extradural thoracic arachnoid cyst: use of MR imaging guidance. J Vasc Interv Radiol 11:369–372, 2000 2. Chang IC, Chou MC, Bell WR, Lin ZI: Spinal cord compression caused by extradural arachnoid cysts. Clinical examples and review. Pediatr Neurosurg 40:70–74, 2004 3. Cloward RB: Congenital spinal extradural cysts: case report with review of literature. Ann Surg 168:851–864, 1968 4. Doita M, Nishida K, Miura J, Takada T, Kurosaka M, Fujii M: Kinematic magnetic resonance imaging of a thoracic spinal extradural arachnoid cyst: an alternative suggestion for exacerbation of symptoms during straining. Spine 28:E229–E233, 2003 5. Hashiguchi K, Morioka T, Fukui K, Miyagi Y, Mihara F, Yoshiura T, et al: Usefulness of constructive interference in steadystate magnetic resonance imaging in the presurgical examination for lumbosacral lipoma. J Neurosurg 103 (6 Suppl): 537–543, 2005

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Manuscript submitted July 18, 2006. Accepted June 27, 2007. Address correspondence to: Takato Morioka, M.D., Ph.D., Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka, 8128582, Japan. email: [email protected].
