- Open Access
Delamination technique together with longitudinal incisions for treatment of Chiari I/syringomyelia complex: a prospective clinical study
© Kotil et al; licensee BioMed Central Ltd. 2009
- Received: 22 February 2009
- Accepted: 22 June 2009
- Published: 22 June 2009
Treatment modalities in Chiari malformation type 1(CMI) accompanied by syringomyelia have not yet been standardized. Pathologies such as a small posterior fossa and thickened dura mater have been discussed previously. Various techniques have been explored to enlarge the foramen magnum and to expand the dura. The aim of this clinical study was to explore a new technique of excision of the external dura accompanied by widening the cisterna magna and making longitudinal incisions in the internal dura, without disturbing the arachnoid.
Ten patients with CMI and syringomyelia, operated between 2004 and 2006, formed this prospective series. All cases underwent foramen magnum decompression of 3 × 3 cm area with C1–C2 (partial) laminectomy, resection of foramen magnum fibrous band, excision of external dura, delamination and widening of internal dura with longitudinal incisions.
Patients were aged between 25 and 58 years and occipital headache was the most common complaint. The mean duration of preoperative symptoms was 4 years and the follow-up time was 25 months. Clinical progression was halted for all patients; eight patients completely recovered and two reported no change. In one patient, there was a transient cerebrospinal fluid (CSF) fistula that was treated with tissue adhesive. While syringomyelia persisted radiologically with radiological stability in five patients; for three patients the syringomyelic cavity decreased in size, and for the remaining two it regressed completely.
Removal of the fibrous band and the outer dural layer, at level of foramen magnum, together with the incision of inner dural layer appears to be good technique in adult CMI patients. The advantages are short operation time, no need for duraplasty, sufficient posterior fossa decompression, absence of CSF fistulas as a result of extra arachnoidal surgery, and short duration of hospitalization. Hence this surgical technique has advantages compared to other techniques.
- Posterior Fossa
- Dura Mater
- Chiari Malformation
- Fibrous Band
Sixty six years after Olivier d'Angers first used the term syringomyelia in 1824, a word that means 'cavity in the spinal cord', H. Chiari described the Chiari malformation, and since Chiari more than a half-century has passed. The etiology and treatment modalities of Chiari malformation continue to be discussed. There are four subtypes of this syndrome of which Chiari malformation Type I (CMI) is the most common. Chiari malformation results in a pressure gradient between the cerebrospinal fluid (CSF) compartments when the cerebellar tonsils descend 3–5 mm or more below the foramen magnum [1–3]. This difference in pressure results in hydrocephaly above the level and syringomyelia below the level. The tonsillary herniation may be symptomatic or not and not every case of CMI is accompanied by syringomyelia. Where syringomyelia exists as in 30%–70% of cases, treatment is required [4, 5]. While surgical therapies in CMI focus on posterior fossa decompression, surgical treatment alternatives for syringomyelia vary widely [3, 5–11]. Suboccipital craniectomy [3, 7], tonsil resection , ventriculo-subarachnoid shunt , syringo-subarachnoid shunt [8, 11], plugging obex , syringo-peritoneal shunt [3, 13] and syringostomy  are the most common ones. In the last decade, widening or decompression of the foramen magnum by microincisions alone , and extra-arachnoidal studies have accelerated and started to focus on splitting the outer leaf of dura without duraplasty [16, 17]. Because complications due to CSF leakage are avoided and operation time is decreased, dural splitting (delamination) is widely preferable and easy to perform .
In our study, using the extra-arachnoidal approach, opening the foramen magnum and the C 1 and C2 laminae, the outer layer of the dura mater was reflected from 3 cm above to 3 cm below the foramen magnum. The second step provided the decompression of the cisterna magna by making longitudinal incisions in the internal dura. This is the first prospective study about this subject using this specific surgical technique.
Between 2004 and 2006, surgery was performed on ten cases with CMI and syringomyelia and the patients were studied prospectively. Following the approval of the local ethics committee, written informed consent was obtained from all of the participants. All clinical symptoms and findings were recorded preoperatively and postoperatively. Neurological examinations of each patient were recorded in detail according to scoring system defined by Asgari et al . All cases underwent surgery as described below and were followed up clinically and radiologically for 25 months.
The patients were evaluated both before and after the surgery. Reflex change, atrophy, pain and temperature dissociation, paresthesia were all recorded on the 1st day, 1st week, 2nd month, 6th month and 2nd year after surgery. The neurological status was graded according to scoring system defined by Asgari et al :
Grade 1: mild (neck pain and headache).
Grade 2: moderate (spinal cord signs exist but function is sufficient). Patients have no myelopathy such as Hoffman's or Babinski signs.
Grade 3: severe (assistance required because unable to use extremities). Patients have myelopathy with Hoffman's and Babinski signs and are unable to use the fingers.
All cases were followed up post-operatively with MRI on day 1, at 2 months, and 2 years. Posterior fossa volumetric values were evaluated from preoperative and postoperative MR images obtained in all cases using the Cavalieri method . Syrinx cavity volumes and regressions, tonsillar ectopy measurements and cisterna magna preoperative and postoperative measurements were all noted.
Symptoms and signs of ten patients with Chiari malformation Type I and syringomyelia.
Symptoms and signs
Sensory disturbances(upper extremity)
Pain radiating from head and neck to arms
Motor weakness(upper extremity)
Loss of temperature and pain sensation
Pyramidal tract signs
Neurological status of ten patients with Chiari malformation Type I and syringomyelia scored with the Asgari scale before and after the surgery.
Number of cases
Radiological and clinical evaluation of the syrinx cavity with MRI of the patients and follow-up time.
Number of cases (10)
Follow-up time (mean & range)
25 mo (13–30)
No major complications were observed. As a minor complication, in only one case (10%), a CSF fistula and wound infection occurred. This resulted from using a surgical lancet (blade) to make the incision after splitting the external dura; for the remaining of cases, the internal dura was opened with a round edged dural hook.
There are several theories regarding the origin of CMI [2, 19–26]. Recently Marin-Padilla has suggested a new theory of partial insufficiency at the time of the mesodermal closure by proposing that the cerebellar tonsils, which pass from a narrow corridor into the spinal canal, impede CSF circulation  and many different surgical techniques have been used in the past. This study has shown that surgery consisting of removal of the fibrous band and the outer dural layer, at level of foramen magnum, together with the incision of inner dural layer had a good outcome in a group of ten patients with CMI and syringomyelia.
Techniques such as opening the dura and treating arachnoid scarring have been used before .
It is known that compared to the normal population, patients with syringomyelia and CMI have a smaller posterior fossa and cisterna magna [28–31]. However, the importance of dural occlusions and dural bands at the level of the foramen magnum in syringomyelia has not previously been described [19–22]. Therefore, for this pathology it has been suggested that the surgical focus should be on the dura without touching the arachnoid [12, 24, 32, 33].
In a study by Matsumato and Symon, surgery using duraplasty gave better results than surgery without duraplasty . Isu et al., in their article published in1993, focused on widening the cisterna magna after foramen magnum decompression using the extradural approach of splitting the outer layer (delamination), and the overall outcome of patients was very satisfactory . Furthermore, Gambardella et al, have studied indirect duraplasty by using transverse microincisions, with an extradural approach without delamination and have published positive results . These previous studies suggest that foramen magnum decompression alone is not sufficiently effective without dural delamination. However, duraplasty has disadvantages in that the long processing time can result in a mixture of blood components in the CSF and in CSF fistulas. Some disadvantages such as systemic complications, high rate of CSF fistulas and long hospitalization periods have been reported in patients who underwent duraplasty and arachnoid dissection [34–36].
In our study, the dura was expanded by reflecting its thicker outer layer and making longitudinal incisions in the inner layer. With time, CSF pulsations enable a remodeling to occur and the cisterna magna enlarges. In all the cases studied here, after approximately 10 months, the cisterna magna had nearly doubled in size. Radiological investigations revealed regression of the syringomyelia within 20 months. Imae et al. in their comparative study, have described four groups who underwent tonsillectomy with duraplasty, intra-arachnoidal lysis with duraplasty, duraplasty alone and delamination alone; the patients were followed up over a long period . They found no significant difference among groups on the degree of reduction of syrinx whereas duraplasty was clearly less invasive compared to tonsillectomy or lysis. They suggested that duraplasty should be the primary surgical procedure for syringomyelia in CMI.
Alzate et al, in their series of 66 cases, stated that if no syringomyelic cavity existed, the dura splitting technique would have rendered better results, however, if the syringomyelic cavity was wide, drainage methods should be added . Moreover, Munshi et al, suggested that if the cavity was not clear enough, results would be more satisfactory with bone decompression alone . Limonadi et al, compared the duraplasty with dural splitting in pediatric patients with CMI and syringomyelia, and showed that dural splitting was more advantageous . However, the dural splitting was performed without making internal dural incisions, as used in our study. They also showed that extra-arachnoidal osseodural decompression had fewer complications, a lower hospitalization period and lower costs than other techniques .
Williams showed that if the dura was left open, CSF circulation would improve . However, Milhorat et al, advocated the opposite . We believe that the dura mater can relax by dividing the outer layer from the inner layer and the result is even better if the inner layer is incised. The dura mater gets thinner while passing through foramen magnum to the spinal canal and its separation gets more difficult [28, 29, 31–33]. In our series, the dura splitting and incisions that we have made up to the cervical 2 were sufficient for a good result.
Concerning the reduction in size of the syringomyelic cavity, the percentage of success is evidently lower in our study than when prior dural and trans-arachnoidal approaches to therapy are performed. However, we believed that, even a moderate or no change on postoperative MR images may be regarded as a worthwhile result when accompanied by clinical recovery. Improved CSF circulation resulted in mild-moderate reduction in the syrinx cavity in 5 of 10 cases, whereas in the remaining patients the syrinx size remained stable on MR images. In these cases there was a significant improvement in the symptoms despite a persistent syrinx. Hence no further surgical procedure was advised to avoid even the minimal rate of risk of shunt complications or major intra-arachnoidal surgical complications.
Nakamura et al, have described before that in CMI, when dura mater histology is examined, there occurs a high production of collagen fibers . Volumetric enlargement of the posterior fossa was not detected in our case. However, strong and thickened fibro-dural bands at the level of foramen magnum were always present and removing this tissue seemed to be the most important factor. This concurs with Nakamura et al. who suggested that the thickening of the dura mater may be causative factor of syringomyelia with CMI . Our data help to verify the hypothesis that performing the simple posterior fossa bone decompression in patients with CMI can achieve comparable results to those obtained with more invasive surgical approaches. Indeed, in our study the percentage of good results is similar to that reported in the literature when more aggressive surgical approaches were used .
Removal of the fibrous band and the outer dural layer, at level of foramen magnum, together with the incision of inner dural layer seems to be good technique for the treatment of syringomyelia in adult CMI patients. The advantages are short operation time, no need for duraplasty, sufficient posterior fossa decompression, absence of CSF fistulas as a result of extra arachnoidal surgery, and short duration of hospitalization. Hence this surgical technique may be superior compared to other techniques.
- Aboulezz AO, Sartor K, Geyer CA, Gado MH: Position of cerebellar tonsils in the normal population and in patients with Chiari malformation: a quantitative approach with MR imaging. J Comput Assist Tomogr. 1985, 9: 1033-1036. 10.1097/00004728-198511000-00005.View ArticlePubMedGoogle Scholar
- Williams B: Simultaneous cerebral and spinal fluid pressure recording. 2. Cerebrospinal dissociation with lesions at the foramen magnum. Acta Neurochir (Wien). 1981, 59: 123-142. 10.1007/BF01411198.View ArticleGoogle Scholar
- Barbaro NM, Wilson CB, Gutin PH, Edwards MS: Surgical treatment of syringomyelia. Favorable results with syringoperitoneal shunting. J Neurosurg. 1984, 61: 531-534. 10.3171/jns.1984.61.3.0531.View ArticlePubMedGoogle Scholar
- Batzdorf U: Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg. 1988, 68: 726-730. 10.3171/jns.1988.68.5.0726.View ArticlePubMedGoogle Scholar
- Cahan LD, Benston JR: Considerations in the diagnosis and treatment of syringomyelia and the Chiari malformation. J Neurosurg. 1982, 57: 24-31. 10.3171/jns.1982.57.1.0024.View ArticlePubMedGoogle Scholar
- Garcia-Uria J, Leunda G, Carrillo R, Bravo G: Syringomyelia: long-term results after posterior fossa decompression. J Neurosurg. 1981, 54: 380-383. 10.3171/jns.1981.54.3.0380.View ArticlePubMedGoogle Scholar
- Gardner WJ: Hydrodynamic mechanism of syringomyelia: its relationship to myelocele. J Neurol Neurosurg Psychiat. 1965, 28: 247-259. 10.1136/jnnp.28.3.247.PubMed CentralView ArticlePubMedGoogle Scholar
- Isu T, Iwasaki Y, Akino M, Abe H: Syringo-subarachnoid shunt for syringomyelia associated with Chiari malformation (type 1). Acta Neurochir (Wien). 1990, 107: 152-160. 10.1007/BF01405795.View ArticleGoogle Scholar
- Matsumoto T, Symon L: Surgical management of syringomyelia-Current results. Surg Neurol. 1989, 32: 258-265. 10.1016/0090-3019(89)90227-9.View ArticlePubMedGoogle Scholar
- Rhoton AL: Microsurgery of Arnold-Chiari malformation in adults with and without hydromyelia. J Neurosurg. 1976, 45: 473-483. 10.3171/jns.1976.45.5.0473.View ArticlePubMedGoogle Scholar
- Tator CH, Meguro K, Rowed DW: Favorable results with syringosubarachnoid shunts for treatment of syringomyelia. J Neurosurg. 1982, 56: 517-523. 10.3171/jns.1982.56.4.0517.View ArticlePubMedGoogle Scholar
- Levy WJ, Mason L, Hahn JF: Chiari malformation presenting in adults: A surgical experience in 127 cases. Neurosurgery. 1983, 12: 377-390.View ArticlePubMedGoogle Scholar
- Philippon J, Sangla S, Lara-Morales J, Gazangel J, Rivierez M, Horn YE: Treatment of syringomyelia by syringo-peritoneal shunt. Acta Neurochir Suppl (Wien). 1988, 43: 32-34.Google Scholar
- Milhorat TH, Johnson WD, Miller JI: Syrinx shunt to posterior fossa cisterns (syringocisternostomy) for bypassing obstructions of upper cervical theca. J Neurosurg. 1992, 77: 871-874. 10.3171/jns.1992.77.6.0871.View ArticlePubMedGoogle Scholar
- Gambardella G, Caruso G, Caffo M, La Rosa G, Tomasello F: Transverse microincisions of the outer layer of the dura mater combined with foramen magnum decompression as treatment for syringomyelia with Chiari I malformation. Acta Neurochir (Wien). 1998, 140: 134-139. 10.1007/s007010050074.View ArticleGoogle Scholar
- Isu T, Sasaki H, Takamura H, Kobayashi N: Foramen magnum decompression with removal of the outer layer of the dura as treatment for syringomyelia occurring with Chiari I malformation. Neurosurgery. 1993, 33: 844-849. 10.1097/00006123-199311000-00009.Google Scholar
- Guyotat J, Bret P, Jouanneau E, Ricci AC, Lapras C: Syringomyelia associated with type I Chiari malformation. A 21-year retrospective study on 75 cases treated by foramen magnum decompression with a special emphasis on the value of tonsils resection. Acta Neurochir (Wien). 1998, 140: 745-754. 10.1007/s007010050175.View ArticleGoogle Scholar
- Asgari S, Engelhorn T, Bschor M, Sandalcioğlu IE, Stolke D: Surgical prognosis in hindbrain related syringomyelia. Acta Neurol Scand. 2003, 107: 12-21. 10.1034/j.1600-0404.2003.01357.x.View ArticlePubMedGoogle Scholar
- Tubbs RS, Webb D, Abdullatif H, Conklin M, Doyle S, Oakes WJ: Posterior cranial fossa volume in patients with rickets: insights into the increased the occurrence of Chiari malformation in metabolic bone disease. Neurosurgery. 2004, 55: 380-383. 10.1227/01.NEU.0000129547.30778.B7.View ArticlePubMedGoogle Scholar
- Blagodatsky MD, Larionov SN, Alexandrov YA, Velm AI: Surgical treatment of Chiari I malformation with or without syringomyelia. Acta Neurochir (Wien). 1999, 141: 963-968. 10.1007/s007010050402.View ArticleGoogle Scholar
- Dure LS, Percy AK, Cheek WR, Laurent JP: Chiari type I malformation in children. J Pediatr. 1989, 115: 573-576. 10.1016/S0022-3476(89)80283-5.View ArticlePubMedGoogle Scholar
- Morgan D, Williams B: Syringobulbia: a surgical appraisal. J Neurol Neurosurg Psychiat. 1992, 55: 1132-1141. 10.1136/jnnp.55.12.1132.PubMed CentralView ArticlePubMedGoogle Scholar
- Nohria V, Oakes WJ: Chiari I malformation: a review of 43 patients. Pediatr Neurosurg. 1991, 16: 222-227. 10.1159/000120531.View ArticleGoogle Scholar
- Oldfield EH, Muraszko K, Shawker TH, Patronas NJ: Pathophysiology of syringomyelia associated with Chiari1 malformation of the cerebellar tonsils. Implications for diagnosis and treatment. J Neurosurg. 1994, 80: 3-15. 10.3171/jns.1994.80.1.0003.View ArticlePubMedGoogle Scholar
- Logue V, Edwards MR: Syringomyelia and its surgical treatment-an analysis of 75 patients. J Neurol Neurosurg Psychiat. 1981, 44: 273-284. 10.1136/jnnp.44.4.273.PubMed CentralView ArticlePubMedGoogle Scholar
- Gardner WJ, Angel J: The mechanism of syringomyelia and its surgical corrections. Clin Neurosurg. 1958, 6: 131-140.PubMedGoogle Scholar
- Marin-Padilla M: Morphogenesis of experimentally induced Arnold-Chiari malformation. J Neurol Sci. 1981, 50: 29-55. 10.1016/0022-510X(81)90040-X.View ArticlePubMedGoogle Scholar
- Wisoff JH: Hydromyelia. A critical review. Childs Nerv Syst. 1988, 4: 1-8.PubMedGoogle Scholar
- Nyland H, Krogness KG: Size of posterior fossa in Chiari type 1 malformation in adults. Acta Neurochir (Wien). 1978, 40: 233-242. 10.1007/BF01774749.View ArticleGoogle Scholar
- Schady W, Metcalfe RA, Butler P: The incidence of craniocervical bony anomalies in the adult Chiari malformation. J Neurol Sci. 1987, 82: 193-203. 10.1016/0022-510X(87)90018-9.View ArticlePubMedGoogle Scholar
- Stovner LJ, Bergan U, Nilsen G, Sjaastad O: Posterior cranial fossa dimensions in the Chiari I malformation: relation to pathogenesis and clinical presentation. Neuroradiology. 1993, 35: 113-118. 10.1007/BF00593966.View ArticlePubMedGoogle Scholar
- Munshi I, Frim D, Reyes SR, Weir BK, Hekmatpanah J, Brown F: Effects of posterior fossa decompression with and without duraplasty on Chiari malformation-associated hydromyelia. Neurosurgery. 2000, 46: 1384-1389. 10.1097/00006123-200006000-00018.View ArticlePubMedGoogle Scholar
- Nakamura N, Iwasaki Y, Hida K, Abe H, Fujioka Y, Nagashima K: Dural band pathology in syringomyelia with Chiari type I malformation. Neuropathology. 2000, 20: 38-43. 10.1046/j.1440-1789.2000.00281.x.View ArticlePubMedGoogle Scholar
- Arora P, Behari S, Banerji D, Chhabra DK, Jain VK: Factors influencing the outcome in symptomatic Chiari 1 malformation. Neurol India. 2004, 52: 470-474.PubMedGoogle Scholar
- Limonadi FM, Selden NR: Dura-splitting decompression of the craniocervical junction: reduced operative time, hospital stay, and cost with equivalent early outcome. J Neurosurg. 2004, 101: 184-188.PubMedGoogle Scholar
- Imae S: Clinical evaluation on etiology and surgical outcome in syringomyelia associated with Chiari type I malformation. No To Shinkei. 1997, 49: 1131-1138.PubMedGoogle Scholar
- Alzate JC, Kothhbauer KF, Jallo GI, Epstein FJ: Treatment of Chiari I malformation in patients with and without syringomyelia: a consecutive series of 66 cases. Neurosurg Focus. 2001, 11: E3-10.3171/foc.2001.11.1.4.View ArticlePubMedGoogle Scholar
- Hida K, Iwasaki Y, Koyanagi I, Sawamura Y, Abe H: Surgical indication and results of foramen magnum decompression versus syringosubarachnoid shunting for syringomyelia associated with Chiari I malformation. Neurosurgery. 1995, 37: 673-678. 10.1097/00006123-199510000-00010.View ArticlePubMedGoogle Scholar
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