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Re-evaluation of foramen magnum decompression with dura left open for Chiari I malformation
Interdisciplinary Neurosurgery 10 (2017) 150–154
Contents lists available at ScienceDirect
Interdisciplinary Neurosurgery journal homepage: www.elsevier.com/locate/inat
Technical Notes & Surgical Techniques
Re-evaluation of foramen magnum decompression with dura left open for Chiari I malformation
MARK
Tetsuryu Mitsuyamaa,b,⁎, Yasuo Aiharaa, Takaomi Tairaa, Seiichiro Eguchia, Kentaro Chibaa, Yoshikazu Okadaa,c, Takakazu Kawamataa a b c
Department of Neurosurgery, Tokyo Women's Medical University, Tokyo, Japan Department of Neurosurgery, Shinagawa Shishoukai Hospital, Tokyo, Japan Department of Neurosurgery, St Luke's International Hospital, Tokyo, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords: Cerebrospinal fluid leak Chiari I malformation Durotomy Foramen magnum decompression
Objective: One of the controversies in foramen magnum decompression (FMD) is the management of dura. Graft adhesion is the most common finding in revisions after FMD with duraplasty. Furthermore, certain number of patients after FMD without dural opening required revision surgery. The most common cause is excessive fibrosis over the preserved dura. On the other hand, FMD with dura left open could reduce the risk for symptomatic recurrence, although it was generally abandoned because of the higher risk of postoperative CSF leakage or meningitis. Purpose of this study was to re-evaluate FMD with dura left open after the application of tight fascial closures in order to reduce the risk of cerebrospinal fluid (CSF) leakage. We compared CSF-related complications of this surgery with other FMD techniques based on literature review. Patients and methods: Our retrospective study included 13 patients who underwent FMD with dura left open. We paid particular attention to prevent CSF leak by the tight suturing of fascial layers especially at both ends of each layer and keeping muscle attachments to inion intact. Results: CSF-related complications and symptomatic recurrence were not observed. The postoperative CSF collection contained within the tightly closed fasciae became of limited size over several months. Conclusion: FMD with dura left open did not show higher rate of CSF leakage as compared to other FMD techniques. The tight closure of fascial layers is essential to minimalize CSF leakage in this surgery. Moreover, it has the advantage of reducing symptomatic recurrence over other FMD techniques.
1. Introduction Foramen magnum decompression (FMD) for Chiari I malformation is a well-established surgical technique, however, there is no general agreement on the details of surgical technique. One of the considerable controversies is the management of dura - without dural opening, with opening only the external dural layer, with keeping dura open, or with expansive duraplasty by different types of grafts. Although duraplasty with artificial dura has gained the greatest popularity, graft adhesion has been reported to be the most common finding in revisions after FMD with duraplasty [1]. It was also reported that about 30% of the patients after FMD without dural opening required revision surgery and thickening of overlying the dura with excessive fibrosis was the most common cause [2]. Therefore, both FMD with duraplasty and FMD without dural opening have the potential risk of symptomatic recur-
⁎
rence by graft adhesion or thickened fibrosis after the procedure. On the other hand, FMD with dura left open, termed “durotomy”, could reduce these potential risks for symptomatic recurrence after surgery. However, FMD with durotomy tended to be abandoned as an old-fashioned surgery with higher risk of complications. These negative impressions have not been confirmed by clinical studies in the current paradigm of global reduction of neurosurgical, especially wound complications. Within this context, we applied the technique with dura remaining open followed by the tight closure of fascial layers. We hypothesized that the tight multilayer closure of fasciae as an effective barrier for cerebrospinal fluid (CSF) could minimalize CSFrelated complications within the contemporary neurosurgical setup. In this study, we did not only provide special attention to the tight closure of fascial layers in FMD with durotomy, but also compared the risk of CSF complications in this procedure with the relevant literature.
Corresponding author at: Department of Neurosurgery, Shinagawa Shishoukai Hospital, 1-29-7 Kitashinagawa, Shinagawa-ku, Tokyo 140-0001, Japan. E-mail address: [email protected] (T. Mitsuyama).
http://dx.doi.org/10.1016/j.inat.2017.09.011 Received 30 June 2017; Received in revised form 21 September 2017; Accepted 30 September 2017 2214-7519/ © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Interdisciplinary Neurosurgery 10 (2017) 150–154
T. Mitsuyama et al.
2. Patients and methods 2.1. Patients We reviewed the medical records of patients who underwent FMD with durotomy for Chiari I malformation at Tokyo Women's Medical University from 2007 to 2015. Patients with secondary Chiari malformation due to craniosynostosis or brain tumors were excluded. We also excluded patients with bony malformations such as basilar impression or structural instability of craniocervical junction (CCJ). Surgical indications were intractable Valsalva headache and/or myelopathy. Thirteen patients (9 women and 4 men) were retrospectively evaluated for their clinical courses and outcomes. We inquired for the presence or absence of CSF-related complications including symptomatic pseudomeningocele, CSF leak, meningitis and hydrocephalus. We also assessed the sequential changes of CSF collections at the operative site on postoperative magnetic resonance (MR) images. The institutional medical ethics board approved this study.
Fig. 2. An additional stich beyond the end of the layer closure with retracting the more superficial layers.
2.2. Surgical technique Patients were positioned prone and their heads were fixed with Mayfield head holder. The upper neck was slightly flexed to improve the visualization of the CCJ. A midline skin incision began in a point just below the external protuberance to extend downwards, confined into the hairy skin as much as possible, especially in female patients. The lower occipital squama, the posterior arch of atlas and the upper part of axis lamina were subperiosteally dissected for exposure after the midline division of subcutaneous tissues and muscular layers through a strict mid-plane incision. The use of monopolar coagulation was avoided or minimalized in order to prevent shrinkage of muscles. Muscles attaching to the inion were left intact to prevent CSF leakage by the insufficient muscle closure in this area. If required, we undercut muscles below their attachment to obtain wider surgical field (Fig. 1). A small sub-occipital craniectomy below the inferior nuchal line with wider exposure than the transverse diameter of the spinal cord was followed by the removal of the posterior arch of atlas. The dura matter was opened in a Y-shape and flaps were reflected. We confirmed the reestablishment of CSF flow by the free pulsatile movements of the tonsils. We added arachnoid dissection or tonisillectomy only if necessary. We left the dura matter open and made an “artificial cisterna magna”, as described by Williams [3], by reconstructing with the vascularized muscle flaps in order to keep the CSF flow re-established. Muscles were loosely sutured at several points to minimalize the ‘dead’ space. To prevent CSF leakage out of this space, we paid special attentions to the tight closure of fascial layers as an effective barrier for CSF pressure. At first, we confirmed adequate hemostasis of muscles and fasciae to avoid blood contamination of CSF. Then, we meticulously sutured each of the
Fig. 3. Absence of air bubbles by pushing the both sides of the saline-covered closure line indicating tight closure.
layers, especially at both incision ends, where we made one more stich beyond the end of the incision line (Fig. 2). The tight closure of each layer was confirmed by the absence of air bubbles when squeezing the wound on both sides after filling it with saline (Fig. 3). Interlayer stitches were added to minimize the ‘dead’ space. The subcutaneous tissues Fig. 1. Muscles attaching to the inion (asterisks) are undercut to expose wider surgical field.
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Fig. 4. A 14-year-old girl with previous FMD surgery (case 11). Intraoperative photograph showing that the dura is left open after tonsillectomy and arachnoid dissection to foramen Magendie (A). Chronological sequence of preoperative (B), follow-up at 4 months (C) and 18 months (D) sagittal MR images demonstrating the formation of “artificial cisterna magna” without CSF penetration through the soft tissues. A postoperative axial image revealing the “artificial cisterna magna” is covered with muscle flaps (E).
are neural compression and CSF flow disturbance at the CCJ. The purposes of FMD are decompression of the neural structures and reestablishment of CSF flow at the CCJ. FMD was first introduced by Gardner in 1949 and the dura was left open in his surgery [4]. To reduce the risk of CSF leak and aseptic meningitis, surgical techniques such as dural plasty by different types of grafts, no dural opening or removal of only the outer dural layer had been introduced. On the other hand, Williams emphasized the need of leaving dura widely open to create an “artificial cisterna magna” for re-establishment of CSF flow at the CCJ [3]. In addition, Klekamp reported graft adhesion as a common operative finding in 45 FMD revisions [1]. Dural plasty in FMD has the possible risks of adhesion or formation of granulations, which causes symptomatic recurrence by compromising CSF flow again at the CCJ [3,5]. Furthermore, Krishna reported that subsequent surgery was necessary in 15 of 47 patients after FMD with only removal of the dural outer layer at an average of 2.6 years after surgery, although 11 patients initially reported complete resolution of symptoms [2]. The most common cause was thickening of the residual dura with excessive fibrosis. FMD without dural opening, even removing only the dural outer layer, also has the possible risk of symptomatic recurrence by insufficient decompression at the CCJ. The purposes of keeping dura open in FMD and creating the “artificial cisterna magna” are to preserve the re-established CSF flow together with sufficient neural decompression and reduce the potential risk of postoperative adhesion. However, FMD with dura left open has the potential risk of CSF leakage. To reduce the risk of CSF leakage when the dura is left open, tight multilayer closure of fasciae is necessary as an effective barrier for CSF leakage to subcutaneous tissues. This type of closure has some important technical details [6]. At first, sufficient hemostasis is necessary for prevention of CSF blood contamination, because it causes aseptic meningitis or adhesive arachnoiditis. Then, muscles are sutured to
and skin were closed in the same manner without placing a drainage tube. 3. Results The mean follow-up period was 37 months (range, 13 to 72). There was no patient with CSF-related complications such as external CSF leaks, pseudomeningocele or meningitis. In all cases, the postoperative CSF collection at the operative site in the short term successfully evolved into an “artificial cisterna magna” without CSF leakage and/or surgical wound bulging (Figs. 4, 5). The mean age of the 13 patients was 27 years (range, 7 to 70) and the following results are summarized in Table 1. Tonsillectomy with arachnoid dissection was performed in two patients: one (case 9) had intractable exertional headache after tonsillar contusion and another (case 11) had progressive myelopathy after previous FMD with duraplasty at another hospital. Syrinx formations were present in eight patients and all of them shrank after surgery. Clinical symptoms improved in all patients except one woman, who had presented with rapid progression of right hemiparesis before surgery and showed deterioration of her weakness after being operated. Her symptoms recovered after several months of rehabilitation. Exertional headache in 9 patients disappeared soon after surgery. There was no recurrence of syringes or any preoperative symptoms. Transient asymptomatic supratentorial subdural CSF collection without cerebellar herniation was observed in one patient. There was neither a postoperative wound CSF leak nor infection. 4. Discussion The main pathophysiological mechanisms of Chiari I malformation
Fig. 5. Postoperative fluid collection at the surgical site was reduced over time without outward CSF leakage (Case 6). Two weeks (A), five weeks (B) and eleven months (C) after surgery.
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Table 1 Demographics and clinical courses of patients with dura left open in FMD. Case
Age/sex
Headache
Myelopathy
Syrinx
Tonsillectomy
F/U, m
Clinical improvement
Complications
1 2 3 4 5 6 7 8 9 10 11 12 13
44/F 9/M 25/F 13/F 7/F 70/F 11/M 38/F 12/F 9/M 14/F 62/M 37/F
+ + − + + − + + + + − + −
+ − + − − + − − − − + − +
+ + + + − + − − − + + − +
− − − − − − − − + − + − −
13 21 26 27 40 54 56 62 62 72 18 18 16
+ + − + + + + + + + + + +
− − Worsening of hemiparesis − − Asymptomatic SDE − − − − − − −
F/U, follow up; F, female; M, male; m, month; SDE, subdural effusion.
minimalize the ‘dead’ space of the operative site, however they must be sutured loosely in order to avoid muscle ischemia. Tight sutures especially at both ends of the incision of each fascial layer are necessary, because they are the most common site of CSF fistulae. The tight closure of each fascial layer can be ascertained at each level by the absence of air bubbles when squeezing the surgical wound from both sides after filling it with saline, just like as fixing a flat tire of a bicycle. Proper interlayer stitches reduce the risk of ‘dead’ space, where the postoperative fluid can pool. To make effective barriers to CSF, we sutured fasciae from three to five layers in this case-series. In addition, keeping the muscle attachments to the inion intact is also essential for preserving an effective musculo-fascial barrier, because their detachments from inion make the tight closure difficult. Even in FMD with dural plasty, Klekamp also mentioned the importance of handling and closure of soft tissues to avoid CSF fistulae and emphasized the role of muscular layers as the most effective barrier to CSF [1]. Therefore, tight fascial sutures play an important role in preventing CSF leakage after FMD with dura left open. On the other hand, it is reported that a thin layer of gelatin sponge over the subdural space during dural closure is effective for preventing meningocerebral adhesion in brain surgery [8]. This method also has potential to reduce the graft adhesion in FMD with duraplasty. Williams reported a new layer formation covering the “artificial cisterna magna” from inside that reconstructs the CSF space and indicates appropriate tissue remodeling [3]. Its morphological formation is considered to be completed over several months, as sequential findings of postoperative MR images showed that the CSF collection surrounded by the tight-sutured fascial layers gradually reduced in size over time. The established mechanisms of tissue remodeling through the process of the surgical wound healing may play a role in this morphological change. Additionally, this remodeling of tissues increases their mechanical strength rapidly up to the sixth week and then the process reaches plateau up to one year in the maturational phase of the wound healing process [7]. Tight closures of fascial layers must be enough strong to prevent outward CSF leakage until the wound mechanical resistance becomes sufficient to counter the CSF pressure. Special attention to tight closure of fascial layers as mentioned above, has the potential of reducing CSF-related complications in FMD with durotomy. On the other hand, the latest knowledge on CSF dynamics proposes three absorption pathways: arachnoid villi, Virchow-Robin spaces and epidural lymphatics [9]. According to this theory, we hypothesized that enhancement of epidural lymphatic drainage at the postoperative CCJ may play an important role in absorbing any residual CSF collection. Recently, there were only three reports on FMD with dura left open [10–12]. Arachnoid dissection was performed in the first of them, additional tonsilar resection in the second and leaving the arachnoid intact in the last one. Complications related to this procedure in 55
patients were evaluated [10,12]. One patient with CSF leak required surgical repair. Two patients developed postoperative hydrocephalus requiring ventriculoperitoneal shunting. Based on these recent papers, complications of FMD with durotomy can be summarized for CSF leaks requiring repair surgery at the rate of 4% and hydrocephalus requiring VP shunt at 3–4%. On the other hand, three other large case series about FMD with duraplasty were also recently reported [13–15]. Additional procedures such as keeping the arachnoid intact, arachnoid dissection and tonsillectomy were different among these three studies. The incidences of CSF-related complications and hydrocephalus in studies about FMD with dural plasty were 4–10% and 3–4% respectively. Given these rates, CSF-related complications of FMD with dura left open are not more frequent than FMD with duraplasty. The principal limitation of this study is not randomized, only observational case-series study with small number of patients. The durotomy is a surgical technique mostly employed in revision surgery of children with posterior fossa tumor, especially after radiation therapy. In this study, six of 13 patients are adult. Case-control study with more cases may reduce such deficiencies. 5. Conclusion FMD with dura left open did not show higher rate of CSF-related complications compared to FMD with duraplasty. Tight closures of fascial layers are important for preventing CSF leak after this surgery. In addition, FMD with dura left open has the potential to reduce the risk of symptomatic recurrence as compared with other FMD surgery. Disclosures The authors have no conflicts of interest in this study. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Acknowledgment The authors thank Kostadin L. Karagiozov, M.D. for reviewing and editing of the manuscript. References [1] J. Klekamp, Neurological deterioration after foramen magnum decompression for Chiari malformation type I: old or new pathology? J. Neurosurg. Pediatr. 10 (2012) 538–547, http://dx.doi.org/10.3171/2012.9.PEDS12110. [2] V. Krishna, M. McLawhorn, L. Kosnik-Infinger, S. Patel, High long-term symptomatic recurrence rates after Chiari-I decompression without dural opening: a single center experience, Clin. Neurol. Neurosurg. 118 (2014) 53–58, http://dx.doi.org/ 10.1016/j.clineuro.2013.12.016. [3] B. Williams, Syringomyelia, Neurosurg. Clin. N. Am. 1 (1990) 653–685 (PMID: 2136163).
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T. Mitsuyama et al. [4] W.J. Gardner, R.J. Goodall, The surgical treatment of Arnold-Chiari malformation in adults; an explanation of its mechanism and importance of encephalography in diagnosis, J. Neurosurg. 7 (1950) 199–206, http://dx.doi.org/10.3171/jns.1950.7. 3.0199. [5] B. Williams, A blast against grafts-on the closing and grafting of the posterior fossa dura, Br. J. Neurosurg. 8 (1994) 275–278 (PMID: 7946015). [6] T. Mitsuyama, T. Sasaki, T. Taira, T. Kawatata, Technical details of the tight closure of fascial-subcutaneous layers without fibrin glue to prevent postoperative cerebrospinal fluid leakage (in Japanese), J. Spine Res. 7 (2016) 1105–1109. [7] M. Leomg, L.G. Phillips, Wound healing, in: C.M. Townsend, Jr.R.D. Beauchamp, B.M. Evers, K.L. Mattox (Eds.), Sabiston Textbook of Surgery, Elsevier, Philadelphia, 2012, pp. 151–171. [8] P. Gonzalez-Lopez, M.V. Harput, H. Türe, B. Atalay, U. Türe, Efficacy of placing a thin layer of gelatin sponge over the subdural space during dural closure in preventing meningo-cerebral adhesion, World Neurosurg. 83 (2015) 93–101, http:// dx.doi.org/10.1016/j.wneu.2014.02.032. [9] T. Brinker, E. Stopa, J. Morrison, P. Klinge, A new look at cerebrospinal fluid circulation, Fluids Barriers CNS 11 (2014) 10, http://dx.doi.org/10.1186/2045-811811-10. [10] P. Perrini, N. Benedetto, R. Tenenbaum, N. Di Lorenzo, Extra-arachnoidal cranio-
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cervical decompression for syringomyelia associated with Chiari I malformation in adults: technique assessment, Acta Neurochir. 149 (2007) 1015–1022, http://dx. doi.org/10.1007/s00701-007-1276-0. D.E. Sakas, S.I. Korfias, S.C. Wayte, D.J. Beale, K.P. Papapetrou, G.S. Stranjalis, K.W. Whittaker, H.L. Whitwell, Chiari malformation: CSF flow dynamics in the craniocervical junction and syrinx, Acta Neurochir. 147 (2005) 1223–1233, http:// dx.doi.org/10.1007/s00701-005-0645-9. M.D. Krieger, J.G. McComb, M.L. Levy, Toward a simpler surgical management of Chiari I malformation in a pediatric population, Pediatr. Neurosurg. 30 (1999) 113–121, http://dx.doi.org/10.1159/000028777. U. Batzdorf, D.L. McArthur, J.R. Bentson, Surgical treatment of Chiari malformation with and without syringomyelia: experience with 177 adult patients, J. Neurosurg. 118 (2013) 232–242, http://dx.doi.org/10.3171/2012.10.JNS12305. J. Klekamp, Surgical treatment of Chiari I malformation—analysis of intraoperative findings, complications, and outcome for 371 foramen magnum decompressions, Neurosurgery 71 (2012) 365–380, http://dx.doi.org/10.1227/NEU. 0b013e31825c3426. A. Alfieri, G. Pinna, Long-term results after posterior fossa decompression in syringomyelia with adult Chiari Type I malformation, J. Neurosurg. Spine 17 (2012) 381–387, http://dx.doi.org/10.3171/2012.7.SPINE12272.
Contents lists available at ScienceDirect
Interdisciplinary Neurosurgery journal homepage: www.elsevier.com/locate/inat
Technical Notes & Surgical Techniques
Re-evaluation of foramen magnum decompression with dura left open for Chiari I malformation
MARK
Tetsuryu Mitsuyamaa,b,⁎, Yasuo Aiharaa, Takaomi Tairaa, Seiichiro Eguchia, Kentaro Chibaa, Yoshikazu Okadaa,c, Takakazu Kawamataa a b c
Department of Neurosurgery, Tokyo Women's Medical University, Tokyo, Japan Department of Neurosurgery, Shinagawa Shishoukai Hospital, Tokyo, Japan Department of Neurosurgery, St Luke's International Hospital, Tokyo, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords: Cerebrospinal fluid leak Chiari I malformation Durotomy Foramen magnum decompression
Objective: One of the controversies in foramen magnum decompression (FMD) is the management of dura. Graft adhesion is the most common finding in revisions after FMD with duraplasty. Furthermore, certain number of patients after FMD without dural opening required revision surgery. The most common cause is excessive fibrosis over the preserved dura. On the other hand, FMD with dura left open could reduce the risk for symptomatic recurrence, although it was generally abandoned because of the higher risk of postoperative CSF leakage or meningitis. Purpose of this study was to re-evaluate FMD with dura left open after the application of tight fascial closures in order to reduce the risk of cerebrospinal fluid (CSF) leakage. We compared CSF-related complications of this surgery with other FMD techniques based on literature review. Patients and methods: Our retrospective study included 13 patients who underwent FMD with dura left open. We paid particular attention to prevent CSF leak by the tight suturing of fascial layers especially at both ends of each layer and keeping muscle attachments to inion intact. Results: CSF-related complications and symptomatic recurrence were not observed. The postoperative CSF collection contained within the tightly closed fasciae became of limited size over several months. Conclusion: FMD with dura left open did not show higher rate of CSF leakage as compared to other FMD techniques. The tight closure of fascial layers is essential to minimalize CSF leakage in this surgery. Moreover, it has the advantage of reducing symptomatic recurrence over other FMD techniques.
1. Introduction Foramen magnum decompression (FMD) for Chiari I malformation is a well-established surgical technique, however, there is no general agreement on the details of surgical technique. One of the considerable controversies is the management of dura - without dural opening, with opening only the external dural layer, with keeping dura open, or with expansive duraplasty by different types of grafts. Although duraplasty with artificial dura has gained the greatest popularity, graft adhesion has been reported to be the most common finding in revisions after FMD with duraplasty [1]. It was also reported that about 30% of the patients after FMD without dural opening required revision surgery and thickening of overlying the dura with excessive fibrosis was the most common cause [2]. Therefore, both FMD with duraplasty and FMD without dural opening have the potential risk of symptomatic recur-
⁎
rence by graft adhesion or thickened fibrosis after the procedure. On the other hand, FMD with dura left open, termed “durotomy”, could reduce these potential risks for symptomatic recurrence after surgery. However, FMD with durotomy tended to be abandoned as an old-fashioned surgery with higher risk of complications. These negative impressions have not been confirmed by clinical studies in the current paradigm of global reduction of neurosurgical, especially wound complications. Within this context, we applied the technique with dura remaining open followed by the tight closure of fascial layers. We hypothesized that the tight multilayer closure of fasciae as an effective barrier for cerebrospinal fluid (CSF) could minimalize CSFrelated complications within the contemporary neurosurgical setup. In this study, we did not only provide special attention to the tight closure of fascial layers in FMD with durotomy, but also compared the risk of CSF complications in this procedure with the relevant literature.
Corresponding author at: Department of Neurosurgery, Shinagawa Shishoukai Hospital, 1-29-7 Kitashinagawa, Shinagawa-ku, Tokyo 140-0001, Japan. E-mail address: [email protected] (T. Mitsuyama).
http://dx.doi.org/10.1016/j.inat.2017.09.011 Received 30 June 2017; Received in revised form 21 September 2017; Accepted 30 September 2017 2214-7519/ © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Interdisciplinary Neurosurgery 10 (2017) 150–154
T. Mitsuyama et al.
2. Patients and methods 2.1. Patients We reviewed the medical records of patients who underwent FMD with durotomy for Chiari I malformation at Tokyo Women's Medical University from 2007 to 2015. Patients with secondary Chiari malformation due to craniosynostosis or brain tumors were excluded. We also excluded patients with bony malformations such as basilar impression or structural instability of craniocervical junction (CCJ). Surgical indications were intractable Valsalva headache and/or myelopathy. Thirteen patients (9 women and 4 men) were retrospectively evaluated for their clinical courses and outcomes. We inquired for the presence or absence of CSF-related complications including symptomatic pseudomeningocele, CSF leak, meningitis and hydrocephalus. We also assessed the sequential changes of CSF collections at the operative site on postoperative magnetic resonance (MR) images. The institutional medical ethics board approved this study.
Fig. 2. An additional stich beyond the end of the layer closure with retracting the more superficial layers.
2.2. Surgical technique Patients were positioned prone and their heads were fixed with Mayfield head holder. The upper neck was slightly flexed to improve the visualization of the CCJ. A midline skin incision began in a point just below the external protuberance to extend downwards, confined into the hairy skin as much as possible, especially in female patients. The lower occipital squama, the posterior arch of atlas and the upper part of axis lamina were subperiosteally dissected for exposure after the midline division of subcutaneous tissues and muscular layers through a strict mid-plane incision. The use of monopolar coagulation was avoided or minimalized in order to prevent shrinkage of muscles. Muscles attaching to the inion were left intact to prevent CSF leakage by the insufficient muscle closure in this area. If required, we undercut muscles below their attachment to obtain wider surgical field (Fig. 1). A small sub-occipital craniectomy below the inferior nuchal line with wider exposure than the transverse diameter of the spinal cord was followed by the removal of the posterior arch of atlas. The dura matter was opened in a Y-shape and flaps were reflected. We confirmed the reestablishment of CSF flow by the free pulsatile movements of the tonsils. We added arachnoid dissection or tonisillectomy only if necessary. We left the dura matter open and made an “artificial cisterna magna”, as described by Williams [3], by reconstructing with the vascularized muscle flaps in order to keep the CSF flow re-established. Muscles were loosely sutured at several points to minimalize the ‘dead’ space. To prevent CSF leakage out of this space, we paid special attentions to the tight closure of fascial layers as an effective barrier for CSF pressure. At first, we confirmed adequate hemostasis of muscles and fasciae to avoid blood contamination of CSF. Then, we meticulously sutured each of the
Fig. 3. Absence of air bubbles by pushing the both sides of the saline-covered closure line indicating tight closure.
layers, especially at both incision ends, where we made one more stich beyond the end of the incision line (Fig. 2). The tight closure of each layer was confirmed by the absence of air bubbles when squeezing the wound on both sides after filling it with saline (Fig. 3). Interlayer stitches were added to minimize the ‘dead’ space. The subcutaneous tissues Fig. 1. Muscles attaching to the inion (asterisks) are undercut to expose wider surgical field.
151
Interdisciplinary Neurosurgery 10 (2017) 150–154
T. Mitsuyama et al.
Fig. 4. A 14-year-old girl with previous FMD surgery (case 11). Intraoperative photograph showing that the dura is left open after tonsillectomy and arachnoid dissection to foramen Magendie (A). Chronological sequence of preoperative (B), follow-up at 4 months (C) and 18 months (D) sagittal MR images demonstrating the formation of “artificial cisterna magna” without CSF penetration through the soft tissues. A postoperative axial image revealing the “artificial cisterna magna” is covered with muscle flaps (E).
are neural compression and CSF flow disturbance at the CCJ. The purposes of FMD are decompression of the neural structures and reestablishment of CSF flow at the CCJ. FMD was first introduced by Gardner in 1949 and the dura was left open in his surgery [4]. To reduce the risk of CSF leak and aseptic meningitis, surgical techniques such as dural plasty by different types of grafts, no dural opening or removal of only the outer dural layer had been introduced. On the other hand, Williams emphasized the need of leaving dura widely open to create an “artificial cisterna magna” for re-establishment of CSF flow at the CCJ [3]. In addition, Klekamp reported graft adhesion as a common operative finding in 45 FMD revisions [1]. Dural plasty in FMD has the possible risks of adhesion or formation of granulations, which causes symptomatic recurrence by compromising CSF flow again at the CCJ [3,5]. Furthermore, Krishna reported that subsequent surgery was necessary in 15 of 47 patients after FMD with only removal of the dural outer layer at an average of 2.6 years after surgery, although 11 patients initially reported complete resolution of symptoms [2]. The most common cause was thickening of the residual dura with excessive fibrosis. FMD without dural opening, even removing only the dural outer layer, also has the possible risk of symptomatic recurrence by insufficient decompression at the CCJ. The purposes of keeping dura open in FMD and creating the “artificial cisterna magna” are to preserve the re-established CSF flow together with sufficient neural decompression and reduce the potential risk of postoperative adhesion. However, FMD with dura left open has the potential risk of CSF leakage. To reduce the risk of CSF leakage when the dura is left open, tight multilayer closure of fasciae is necessary as an effective barrier for CSF leakage to subcutaneous tissues. This type of closure has some important technical details [6]. At first, sufficient hemostasis is necessary for prevention of CSF blood contamination, because it causes aseptic meningitis or adhesive arachnoiditis. Then, muscles are sutured to
and skin were closed in the same manner without placing a drainage tube. 3. Results The mean follow-up period was 37 months (range, 13 to 72). There was no patient with CSF-related complications such as external CSF leaks, pseudomeningocele or meningitis. In all cases, the postoperative CSF collection at the operative site in the short term successfully evolved into an “artificial cisterna magna” without CSF leakage and/or surgical wound bulging (Figs. 4, 5). The mean age of the 13 patients was 27 years (range, 7 to 70) and the following results are summarized in Table 1. Tonsillectomy with arachnoid dissection was performed in two patients: one (case 9) had intractable exertional headache after tonsillar contusion and another (case 11) had progressive myelopathy after previous FMD with duraplasty at another hospital. Syrinx formations were present in eight patients and all of them shrank after surgery. Clinical symptoms improved in all patients except one woman, who had presented with rapid progression of right hemiparesis before surgery and showed deterioration of her weakness after being operated. Her symptoms recovered after several months of rehabilitation. Exertional headache in 9 patients disappeared soon after surgery. There was no recurrence of syringes or any preoperative symptoms. Transient asymptomatic supratentorial subdural CSF collection without cerebellar herniation was observed in one patient. There was neither a postoperative wound CSF leak nor infection. 4. Discussion The main pathophysiological mechanisms of Chiari I malformation
Fig. 5. Postoperative fluid collection at the surgical site was reduced over time without outward CSF leakage (Case 6). Two weeks (A), five weeks (B) and eleven months (C) after surgery.
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Table 1 Demographics and clinical courses of patients with dura left open in FMD. Case
Age/sex
Headache
Myelopathy
Syrinx
Tonsillectomy
F/U, m
Clinical improvement
Complications
1 2 3 4 5 6 7 8 9 10 11 12 13
44/F 9/M 25/F 13/F 7/F 70/F 11/M 38/F 12/F 9/M 14/F 62/M 37/F
+ + − + + − + + + + − + −
+ − + − − + − − − − + − +
+ + + + − + − − − + + − +
− − − − − − − − + − + − −
13 21 26 27 40 54 56 62 62 72 18 18 16
+ + − + + + + + + + + + +
− − Worsening of hemiparesis − − Asymptomatic SDE − − − − − − −
F/U, follow up; F, female; M, male; m, month; SDE, subdural effusion.
minimalize the ‘dead’ space of the operative site, however they must be sutured loosely in order to avoid muscle ischemia. Tight sutures especially at both ends of the incision of each fascial layer are necessary, because they are the most common site of CSF fistulae. The tight closure of each fascial layer can be ascertained at each level by the absence of air bubbles when squeezing the surgical wound from both sides after filling it with saline, just like as fixing a flat tire of a bicycle. Proper interlayer stitches reduce the risk of ‘dead’ space, where the postoperative fluid can pool. To make effective barriers to CSF, we sutured fasciae from three to five layers in this case-series. In addition, keeping the muscle attachments to the inion intact is also essential for preserving an effective musculo-fascial barrier, because their detachments from inion make the tight closure difficult. Even in FMD with dural plasty, Klekamp also mentioned the importance of handling and closure of soft tissues to avoid CSF fistulae and emphasized the role of muscular layers as the most effective barrier to CSF [1]. Therefore, tight fascial sutures play an important role in preventing CSF leakage after FMD with dura left open. On the other hand, it is reported that a thin layer of gelatin sponge over the subdural space during dural closure is effective for preventing meningocerebral adhesion in brain surgery [8]. This method also has potential to reduce the graft adhesion in FMD with duraplasty. Williams reported a new layer formation covering the “artificial cisterna magna” from inside that reconstructs the CSF space and indicates appropriate tissue remodeling [3]. Its morphological formation is considered to be completed over several months, as sequential findings of postoperative MR images showed that the CSF collection surrounded by the tight-sutured fascial layers gradually reduced in size over time. The established mechanisms of tissue remodeling through the process of the surgical wound healing may play a role in this morphological change. Additionally, this remodeling of tissues increases their mechanical strength rapidly up to the sixth week and then the process reaches plateau up to one year in the maturational phase of the wound healing process [7]. Tight closures of fascial layers must be enough strong to prevent outward CSF leakage until the wound mechanical resistance becomes sufficient to counter the CSF pressure. Special attention to tight closure of fascial layers as mentioned above, has the potential of reducing CSF-related complications in FMD with durotomy. On the other hand, the latest knowledge on CSF dynamics proposes three absorption pathways: arachnoid villi, Virchow-Robin spaces and epidural lymphatics [9]. According to this theory, we hypothesized that enhancement of epidural lymphatic drainage at the postoperative CCJ may play an important role in absorbing any residual CSF collection. Recently, there were only three reports on FMD with dura left open [10–12]. Arachnoid dissection was performed in the first of them, additional tonsilar resection in the second and leaving the arachnoid intact in the last one. Complications related to this procedure in 55
patients were evaluated [10,12]. One patient with CSF leak required surgical repair. Two patients developed postoperative hydrocephalus requiring ventriculoperitoneal shunting. Based on these recent papers, complications of FMD with durotomy can be summarized for CSF leaks requiring repair surgery at the rate of 4% and hydrocephalus requiring VP shunt at 3–4%. On the other hand, three other large case series about FMD with duraplasty were also recently reported [13–15]. Additional procedures such as keeping the arachnoid intact, arachnoid dissection and tonsillectomy were different among these three studies. The incidences of CSF-related complications and hydrocephalus in studies about FMD with dural plasty were 4–10% and 3–4% respectively. Given these rates, CSF-related complications of FMD with dura left open are not more frequent than FMD with duraplasty. The principal limitation of this study is not randomized, only observational case-series study with small number of patients. The durotomy is a surgical technique mostly employed in revision surgery of children with posterior fossa tumor, especially after radiation therapy. In this study, six of 13 patients are adult. Case-control study with more cases may reduce such deficiencies. 5. Conclusion FMD with dura left open did not show higher rate of CSF-related complications compared to FMD with duraplasty. Tight closures of fascial layers are important for preventing CSF leak after this surgery. In addition, FMD with dura left open has the potential to reduce the risk of symptomatic recurrence as compared with other FMD surgery. Disclosures The authors have no conflicts of interest in this study. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Acknowledgment The authors thank Kostadin L. Karagiozov, M.D. for reviewing and editing of the manuscript. References [1] J. Klekamp, Neurological deterioration after foramen magnum decompression for Chiari malformation type I: old or new pathology? J. Neurosurg. Pediatr. 10 (2012) 538–547, http://dx.doi.org/10.3171/2012.9.PEDS12110. [2] V. Krishna, M. McLawhorn, L. Kosnik-Infinger, S. Patel, High long-term symptomatic recurrence rates after Chiari-I decompression without dural opening: a single center experience, Clin. Neurol. Neurosurg. 118 (2014) 53–58, http://dx.doi.org/ 10.1016/j.clineuro.2013.12.016. [3] B. Williams, Syringomyelia, Neurosurg. Clin. N. Am. 1 (1990) 653–685 (PMID: 2136163).
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