A Review of Controversial Topics

Controversies in the diagnosis and management of adult Chiari Malformation (CM; the Chiari I malformation) and syringomyelia abound. They include, but are not limited to, those listed in outline form below. This discussion does not focus on the Chiari II malformation, which is associated with other congenital conditions and malformations.45,46 A brief discussion of each controversy is provided, with selected references for further study if desired.

1. Indications for surgery for CM

The etiology (cause) of CM varies (and is often unknown), as do the indications for surgery.1,8,16,28,38,39,40,44,49,52,67 The presence of a Chiari malformation DOES NOT, in and of itself, provide sufficient rationale for an indication for surgery. Most neurosurgeons reserve surgery for the symptomatic patient with correlative imaging findings.6,17 Symptoms consistent with brainstem compression (swallowing difficulties, diminished gag reflex, speech difficulties, etc) or an associated symptomatic syringomyelia (signs of spinal cord dysfunction, such as weakness or gait disturbance) are usually requisite findings that suggest an indication for surgery. In addition, signs of an intracranial/spinal pressure differential (tussive [cough related] headaches,59 the presence of an associated syrinx, etc) are often considered indicators for surgery. Vague symptoms such as chronic fatigue, non-specific headache symptoms, general aches and pains, etc are generally not considered to be associated with a surgically treatable Chiari malformation.1 Many surgeons utilize cine flow studies (a modification of a routine MRI that assesses CSF flow in the spaces around the CM) as a tool to determine indications for surgery.3,9,13,20

2. Indications for surgery for syringomyelia

The indications for surgery for syringomyelia, likewise, vary widely. In the presence of a Chiari malformation, the 2 Revised 07/2009 syrinx may be effectively treated by a Chiari decompression procedure. 7,42 In the absence of a Chiari malformation, trauma, prior hemorrhage, prior surgery, or prior meningitis may be implicated.11,12 Oftentimes, the etiology or cause of an isolated syrinx is unknown. Regardless, management is controversial and depends on several factors including age (for example, less likely to treat asymptomatic adults than asymptomatic children), presence or absence of symptoms, size of the syrinx, whether a readily treatable cause such as CM or a tethered cord is presents

3. Indications for occiput to spinal fusion or C1-C2 fusion, with or without anterior decompression (usually via the transoral route)

Occiput to spinal or C1-2 fusion for Chiari malformation is rarely indicated. Such may be the case when severe basilar invagination (angulation of the skull base with respect to the axis of the spine), in which anterior brainstem compression is present at the base of the skull (foramen magnum).18,26 Such a fusion is clearly indicated if an anterior decompression via the transoral resection of the odontoid process (top portion of the C2 vertebra) is performed.7 Controversies arise depending on the extent of skull base angulation (e.g., how severe should the angulation be before a fusion is recommended?), symptomatic state, response to prior surgery for Chiari decompression, and others.

4. Indications for tethered cord release

A tethered spinal cord is uncommonly associated with CM or syringomyelia. When a tethered cord is obviously present on MRI, surgery is often indicated to prevent neurological and bladder dysfunction. Recent claims that tethering of the spinal cord may occur in CM patients without MRI evidence of “occult tethered cord” are fraught with controversy. 41,56 3 Revised 07/2009

5. Operative strategy options for CM –Tonsil coagulation

The need for bony decompression – When a Chiari decompression is indicated, bony decompression of the foramen magnum and C1 arch is thought by most surgeons to be necessary. This opinion, however, is not universally held.64,65

The need for dural opening – After bony decompression, opening the dural covering of the foramen magnum is thought to be necessary by 80-90% of neurosurgeons. The rest, however, are convinced that bone decompression is all that is required.

Arachnoid opening – After opening of the dura mater during a Chiari malformation operation, many surgeons attempt to preserve the integrity of the arachnoid in order to minimize surgical manipulation and subsequent scarring in the subarachnoid space. Others feel that such is necessary in order to adequately decompress.

Tonsil coagulation – Of the surgeons who recommend arachnoid opening, many recommend tonsil shrinkage by coagulation or other means. The tonsils represent the lower portion of the cerebellum that descend through the foramen magnum in a Chiari patient. Those who argue for such a procedure state that decompression of the ‘crowded space’ in the region of the foramen magnum is enhanced by such a technique. Those who argue against this strategy, state that scarring is induced in the subarachnoid space by such a surgical intervention. 19

The use of traditional open versus endoscopic approaches – Opinions vary regarding the use of traditional open versus endoscopic approaches to CM. Although most surgeons utilize the open approach, some state that the same 4 Revised 07/2009 results can be obtained with less invasive approaches. Obviously, an endoscopic approach has limitations regarding bone removal, etc. If such is not felt to be relevant in a specific case, many would consider a less invasive endoscopic approach. The major controversy regarding the endoscopic approach, however, is that it consists of endoscopic tonsillar shrinkage with minimal bone removal and dural opening. Some contend that the long-term possibility of scar formation secondary to tonsillar shrinkage has not yet been adequately addressed to warrant wider use of this procedure.

Dural closure – When the dura is opened, most surgeons recommend dural closure at the end of the procedure. A minority of surgeons, however, state that such closure is not necessary and may even increase the risk of dural scarring to underlying neural structures. Interestingly, neither technique has been shown to be superior so far.

Indications for the use of a dural patch – When dural closure is performed, a patch is usually placed, which expands the dural sac, presumably allowing for a more depends usually dependent on surgeon preference.23

The choice of dural patch material – Many patch materials are available, ranging from autogenous (local, patient’s own) tissue to a variety of cadaveric, animal, and artificial materials.10 Local patch material can be obtained from the pericranium (tissue overlying the skull), ligamentum nuchae (midline tissue in the neck), and other sources.15

  • Indications for a simultaneous syrinx shunt – Most surgeons, when faced with a CM and an associated syrinx, simply decompress the CM. Some, however, 5 Revised 07/2009 recommend shunting the syrinx as well. Those who simply decompress the CM argue that the shunting procedure adds unnecessary risk.
  • The extent of bony decompression – Currently, most surgeons decompress the occiput to a lesser extent than in years gone by. Usually about a 1 x 2 cm portion of occiput, as well as the lamina of C1, are resected. Extensive resection of occipital bone can result in recurrent and relatively refractory symptoms due to the sagging of the cerebellum (cerebellar ptosis).24
6. Operative strategy options for syringomyelia 4,29,34,35,47,48,61,69

The etiology (cause) of syringomyelia is not always obvious. Tumor,57 trauma, 55,62,63 and CSF inflammatory process are but a few. Most often, however, the diagnosis is not known and the syrinx is stated to be idiopathic in nature. To complicate matters further, syringomyelia has been observed in rare circumstances to spontaneously regress without treatment.66

    • Syrinx shunting procedures – Although the mainstay of treatment for idiopathic or posttraumatic syringomyelia for years, shunting procedures have been shown in recent years to be fraught with peril and have therefore fallen into disfavor. 55,60,70 Most surgeons shy away from such strategies due to low long term efficacy, risk of spinal cord injury during placement and the inability to detect shunt patency postoperatively. Nevertheless, shunting procedures are appropriately employed in selected cases. Several types of shunts may be used. These are detailed in another section and have their own inherent controversies: Syringo-subarachnoid shunt – Syringo-subarachnoid shunts drain the syrinx fluid into the spinal 6 Revised 07/2009 fluid space (subarachnoid space). This procedure is the easiest to perform of the three.2,14,22,30,51
    • Syringo-pleural shunt – Syringo-pleural shunts drain the syrinx into the space outside the lung. Pneumothorax and hydrothorax are complications of this procedure.
    • Syringo-peritoneal shunt – Syringo-peritoneal shunts drain the syrinx fluid into the peritoneal or abdominal cavity.33,54

Procedures that restore CSF pathway patency – Trauma, meningitis, previous surgery and others may cause scarring in the CSF pathways (arachnoiditis). In turn, this arachnoiditis may cause blockage of CSF flow and resultant neurological dysfunction with or without syringomyelia. The restoration of CSF flow by creating a larger space (via a laminectomy or a CM decompression and the placement of a dural patch graft)53,68 may be helpful, even in cases where there is no obvious CM.27 The maintenance of restored CSF flow, however, is often problematic.21

Adjuncts to subarachnoid CSF flow re-establishment strategies

    • The use of scar inhibition strategies – Scar inhibition strategies may be employed following a CSF restoration procedure. Such techniques include the application of scar inhibiting material such as collagen-based dural graft matrices.
    • The use of a dural patch – A dural patch is usually employed with CSF flow restoration techniques. Such provides more room for CSF to flow. 7 Revised 07/2009
    • The management of arachnoiditis, syringomyelia and recurrent syringomyelia – The management of recurrent syringomyelia in the face of arachnoiditis is fraught with peril and is therefore very controversial. The employment of the aforementioned techniques may be useful, but the outcome is often suboptimal.31,32,36 Surgery, therefore, is usually reserved for the neurologically deteriorating patient.

Spinal decompression and deformity correction strategies – Sometimes, syringomyelia is associated with spinal column deformities (scoliosis, kyphosis, etc.). It is often difficult to know whether the deformity is the cause or result of the syrinx. It may also be difficult to sort out whether the neurological dysfunction caused or was the result of the spinal deformity. In such complex cases, spinal decompression and deformity correction strategies may be indicated as adjuncts to syrinx treatment.5,37,43,50,58 8


  1. Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ: Treatment of Chiari I malformation in patients with and without syringomyelia: a consecutive series of 66 cases. Neurosurg Focus 15;11(1):E3, 2001.
  2. Aoyama T, Ohtaki M, Koyanagi I, Kawamura M, Chiba M: Syringo-subarachnoidal shunting to correct unilateral leg deformity in a child with terminal syringomyelia: case report. Childs Nerv Syst 24(7):869-73, 2008; Epub 2008 Mar 20, 2008.
  3. Armonda RA, Citrin CM, Foley KT, Ellenbogen RG: Quantitative cine-mode magnetic resonance imaging of Chiari I malformations: an analysis of cerebrospinal fluid dynamics. Neurosurgery 35:214-223; discussion 223-214, 1994
  4. Asano M, Fujiwara K, Yonenobu K, Hiroshima K: Post-traumatic syringomyelia. Spine 21(12):1446-53, 1996.
  5. Bains RS, Althausen PL, Gitlin GN, Gupta MC, Benson DR: The role of acute decompression and restoration of spinal alignment in the prevention of post-traumatic syringomyelia: case report and review of recent literature. Spine 26(17):E399-402, 2001.
  6. Batzdorf U: Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg 68:726-730, 1988 9 Revised 07/2009
  7. Batzdorf U: Syringomyelia related to abnormalities of the Craniovertebral Junction. Baltimore: Williams & Wilkins, 1991
  8. Batzdorf U: Syringomyelia, Chiari Malformations, and Hydromyelia, ed 4. Philadelphia: WB Saunders, 1996
  9. RA, Bogdan AR, Wolpert SM, Lev S, Appignani BA, Heilman CB: Cerebrospinal fluid flow waveforms: analysis in patients with Chiari I malformation by means of gated phase-contrast MR imaging velocity measurements. Radiology 196:195-202, 1995
  10. Blackburn SL, Smyth MD: Hydrogel-induced cervicomedullary compression after posterior fossa decompression for Chiari malformation. Case report. J Neurosurg 106(4 Suppl):302-4, 2007
  11. Bollen AE, Hoving EW, Kuks JB; Posttraumatic syringomyelia in 2 patients with thoracic spinal cord lesions. Ned Tijdschr Geneeskd 144(18):850-4, 2000. (Dutch)
  12. Cao F, Yang XF, Liu WG, Li G, Zheng XS, Wen L; Surgery for posttraumatic syringomyelia: a retrospective study of seven patients. Chin J Traumatol 10(6):366-70, 2007. 10 Revised 07/2009
  13. Carpenter PW, Berkouk K, Lucey AD.; Pressure wave propagation in fluid-filled co-axial elastic tubes. Part 2: Mechanisms for the pathogenesis of syringomyelia. J Biomech Eng 125(6):857-63, 2003.
  14. Colak A, Boran BO, Kutlay M, Demirican N: A modified technique for syringosubarachnoid shunt for treatment of syringomyelia. J Clin Neurosci 12(6):677-9, 2005.
  15. Danish SF, Samdani A, Hanna A, Storm P, Sutton L: Experience with acellular human dura and bovine collagen matrix for duraplasty after posterior fossa decompression for Chiari malformations. J Neurosurg 104(1 Suppl):16-20, 2006.
  16. Dyste GN, Menezes AH, VanGilder JC: Symptomatic Chiari malformations. An analysis of presentation, management, and long-term outcome. J Neurosurg 71:159-168, 1989
  17. Elster AD, Chen MY: Chiari I malformations: clinical and radiologic reappraisal. Radiology 183:347-353, 1992
  18. Fehlings MG, Errico T, Cooper P, Benjamin V, DiBartolo T: Occipitocervical fusion with a five-millimeter malleable rod and segmental fixation. Neurosurgery 32(2):198- 207; discussion 207-8, 1993 11 Revised 07/2009
  19. Guyotat J, Bret P, Mottolese C, Jouhanneau E, Abdulrahman M, Lapras C: Chiari I malformation with syringomyelia treated by decompression of the cranio-spinal junction and tonsillectomy. Apropos of 8 cases. Neurochirurgie 43(3):135-41, 1997. (French)
  20. Heiss JD, Patronas N, DeVroom HL, Shawker T, Ennis R, Kammerer W, Eidsath A, Talbot T, Morris J, Eskioglu E, Oldfield EH: Elucidating the pathophysiology of syringomyelia. J Neurosurg 91(4):553-62, 1999.
  21. Hida K, Iwasaki Y, Imamura H, Abe H.; Posttraumatic syringomyelia: its characteristic magnetic resonance imaging findings and surgical management. Neurosurgery 35(5):886-91; discussion 891, 1994.
  22. 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 37:673-678; discussion 678-679, 1995
  23. Hoffman CE, Souweidane MM: Cerebrospinal fluid-related complications with autologous duraplasty and arachnoid sparing in type I Chiari malformation. Neurosurgery 62(3 Suppl 1):156-60; discussion 160-1, 2008.
  24. Holly LT, Batzdorf U: Management of cerebellar ptosis following craniovertebral decompression for Chiari I malformation. J Neurosurg 94(1):21-6, 2001 12 Revised 07/2009
  25. Holly LT, Johnson JP, Masciopinto JE, Batzdorf U: Treatment of posttraumatic syringomyelia with extradural decompressive surgery. Neurosurg Focus 15;8(3):E8, 2000.
  26. Hwang SW, Heilman CB, Riesenburger RI, Kryzanski J: C1-C2 arthrodesis after transoral odontoidectomy and suboccipital craniectomy for ventral brain stem compression in Chiari I patients. Eur Spine J 17(9):1211-7. Epub 2008 Jul 16, 2008.
  27. Iskandar BJ, Hedlund GL, Grabb PA, Oakes WJ: The resolution of syringohydromyelia without hindbrain herniation after posterior fossa decompression. J Neurosurg 89:212- 216, 1998
  28. Iskandar B, Oakes W: The Chiari Malformations, in Albright A, Pollack I, Adelson P (eds): Principles and Practice of Pediatric Neurosurgery, ed 1st. New York, NY: Thieme Medical Publishers, 1999
  29. Iskandar BJ, Oakes WJ, McLaughlin C, Osumi AK, Tien RD: Terminal syringohydromyelia and occult spinal dysraphism. J Neurosurg 81:513-519, 1994
  30. Jea A, Navarro R, Green BA.; Rapid expansion of a ventral arachnoid cyst after syringosubarachnoid shunting in the thoracic spinal cord: case report. Surg Neurol 64(1):86-9; discussion 89, 2005. 13 Revised 07/2009
  31. Klekamp J, Batzdorf U, Samii M, Bothe HW: Treatment of syringomyelia associated with arachnoid scarring caused by arachnoiditis or trauma. J Neurosurg 86:233-240, 1997
  32. Koyanagi I, Iwasaki Y, Hida K, Houkin K: Clinical features and pathomechanisms of syringomyelia associated with spinal arachnoiditis. Surg Neurol 63(4):350-5; discussion 355-6, 2005.
  33. Lam S, Batzdorf U, Bergsneider M: Thecal shunt placement for treatment of obstructive primary syringomyelia. J Neurosurg Spine 9(6):581-8, 2008.
  34. La Marca F, Herman M, Grant JA, McLone DG: Presentation and management of hydromyelia in children with Chiari type-II malformation. Pediatr Neurosurg 26:57-67, 1997
  35. Lee TT, Alameda GJ, Camilo E, Green BA: Surgical treatment of post-traumatic myelopathy associated with syringomyelia. Spine 15;26(24 Suppl):S119-27, 2001.
  36. Lee TT, Alameda GJ, Gromelski EB, Green BA: Outcome after surgical treatment of progressive posttraumatic cystic myelopathy. J Neurosurg 92(2 Suppl):149-54, 2000. 14 Revised 07/2009
  37. Lee JH, Chung CK, Kim HJ: Decompression of the spinal subarachnoid space as a solution for syringomyelia without Chiari malformation.. Spinal Cord 40(10):501-6, 2002.
  38. Levy WJ, Mason L, Hahn JF: Chiari malformation presenting in adults: a surgical experience in 127 cases. Neurosurgery 12:377-390, 1983
  39. Mampalam TJ, Andrews BT, Gelb D, Ferriero D, Pitts LH: Presentation of type I Chiari malformation after head trauma. Neurosurgery 23:760-762, 1988
  40. Mikulis DJ, Diaz O, Egglin TK, Sanchez R: Variance of the position of the cerebellar tonsils with age: preliminary report. Radiology 183:725-728, 1992
  41. Milhorat TH, Bolognese PA, Nishikawa M, Francomano CA, McDonnell NB, Roonprapunt C, Kula RW: Association of Chiari malformation type I and tethered cord syndrome: preliminary results of sectioning filum terminale. Surg Neurol 72(1):20-35, 2009.
  42. Menezes AH: Chiari I malformations and hydromyelia–complications. Pediatr Neurosurg 17:146-154, 1991
  43. Muhonen MG, Menezes AH, Sawin PD, Weinstein SL: Scoliosis in pediatric Chiari malformations without myelodysplasia. J Neurosurg 77:69-77, 1992 15 Revised 07/2009
  44. Nagib MG: An approach to symptomatic children (ages 4-14 years) with Chiari type I malformation. Pediatr Neurosurg 21:31-35, 1994
  45. Naidich TP, McLone DG, Fulling KH: The Chiari II malformation: Part IV. The hindbrain deformity. Neuroradiology 25:179-197, 1983
  46. Naidich TP, Pudlowski RM, Naidich JB, Gornish M, Rodriguez FJ: Computed tomographic signs of the Chiari II malformation. Part I: Skull and dural partitions. Radiology 134:65-71, 1980
  47. Nakamura M, Ishii K, Watanabe K, Tsuji T, Matsumoto M, Toyama Y, Chiba K.; Clinical significance and prognosis of idiopathic syringomyelia. J Spinal Disord Tech 22(5):372-5, 2009.
  48. Nielsen OA, Biering-Sørensen F, Mosdal C.; Post-traumatic syringomyelia]. Ugeskr Laeger 14;165(29):2879-82, 2003. (Danish)
  49. Nohria V, Oakes WJ: Chiari I malformation: a review of 43 patients. Pediatr Neurosurg 16:222-227, 1990
  50. Ono A, Ueyama K, Okada A, Echigoya N, Yokoyama T, Harata S: Adult scoliosis in syringomyelia associated with Chiari I malformation. Spine 27:E23-28, 2002 16 Revised 07/2009
  51. Padovani R, Cavallo M, Gaist G.; Surgical treatment of syringomyelia: favorable results with syringosubarachnoid shunting. Surg Neurol 32(3):173-80, 1989.
  52. Paul KS, Lye RH, Strang FA, Dutton J: Arnold-Chiari malformation. Review of 71 cases. J Neurosurg 58:183-187, 1983
  53. Peng L, Qi ST, Zhu WL: Modified reconstruction of the cistern magna for treatment of syringomyelia with Chiari malformation: clinical analysis of 35 cases. Nan Fang Yi Ke Da Xue Xue Bao 29(2):284-8, 2009. (Chinese)
  54. Philippon J, Sangla S, Lara-Morales J, Gazengel J, Rivierez M, Horn YE.; Treatment of syringomyelia by syringo-peritoneal shunt. Acta Neurochir Suppl (Wien) 43:32-4, 1988
  55. Potter K, Saifuddin A: Pictorial review: MRI of chronic spinal cord injury. Br J Radiol 76:347-352, 2003
  56. Sade B, Beni-Adani L, Ben-Sira L, Constantini S.; Progression of terminal syrinx in occult spina bifida after untethering. Childs Nerv Syst 19(2):106-8, 2003. Epub 2002 Nov 13.
  57. Samii M, Klekamp J: Surgical results of 100 intramedullary tumors in relation to accompanying syringomyelia. Neurosurgery 35:865-873; discussion 873, 1994 17 Revised 07/2009
  58. Samuelsson L, Bergstrom K, Thuomas KA, Hemmingsson A, Wallensten R: MR imaging of syringohydromyelia and Chiari malformations in myelomeningocele patients with scoliosis. AJNR Am J Neuroradiol 8:539-546, 1987
  59. Sansur CA, Heiss JD, DeVroom HL, Eskioglu E, Ennis R, Oldfield EH.; Pathophysiology of headache associated with cough in patients with Chiari I malformation. J Neurosurg 98(3):453-8, 2003.
  60. Sgouros S, Williams B.; A critical appraisal of drainage in syringomyelia. J Neurosurg 82(1):1-10, 1995.
  61. Sgouros S, Williams B: A critical appraisal of pediculated omental graft transposition in progressive spinal cord failure. Br J Neurosurg 10(6):547-53, 1996.
  62. Sgouros S, Williams BL: Management and outcome of posttraumatic syringomyelia. J Neurosurg 85(2):197-205, 1996.
  63. Silberstein M, Tress BM, Hennessy O: Delayed neurologic deterioration in the patient with spinal trauma: role of MR imaging. AJNR Am J Neuroradiol 13:1373-1381, 1992
  64. Sindou M, Chávez-Machuca J, Hashish H. Cranio-cervical decompression for Chiari type I-malformation, adding extreme lateral foramen magnum opening and expansile duroplasty with arachnoid preservation. Technique and long-term functional results in 44 18 Revised 07/2009 consecutive adult cases — comparison with literature data. Acta Neurochir (Wien) 144(10):1005-19., 2002
  65. Sindou M, Gimbert E.; Decompression for Chiari type I-malformation (with or without syringomyelia) by extreme lateral foramen magnum opening and expansile duraplasty with arachnoid preservation: comparison with other technical modalities (Literature review). Adv Tech Stand Neurosurg 34:85-110, 2009. Review.
  66. Sung WS, Chen YY, Dubey A, Hunn A: Spontaneous regression of syringomyelia– review of the current aetiological theories and implications for surgery. J Clin Neurosci. 15(10):1185-8, 2008. Epub 2008 Aug 16. Review.
  67. Tubbs RS, McGirt MJ, Oakes WJ: Surgical experience in 130 pediatric patients with Chiari I malformations. J Neurosurg 99:291-296, 2003
  68. Wetjen NM, Heiss JD, Oldfield EH: Time course of syringomyelia resolution following decompression of Chiari malformation Type I. J Neurosurg Pediatr 1(2):118-23, 2008.
  69. Williams B: Post-traumatic syringomyelia, an update. Paraplegia 28(5):296-313, 1990.
  70. Williams B, Sgouros S, Nenji E; Cerebrospinal fluid drainage for syringomyelia. Eur J Pediatr Surg 5 Suppl 1:27-30, 1995.


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