Obex position is associated with syringomyelia and use of posterior fossa decompression among patients with Chiari I malformation

View More View Less
  • 1 Departments of Neurological Surgery,
  • 2 Neurology,
  • 3 Orthopaedic Surgery, and
  • 5 Pediatrics, Washington University School of Medicine; and
  • 4 Shriners Hospital for Children, St. Louis, Missouri
Restricted access

Purchase Now

USD  $45.00

JNS + Pediatrics - 1 year subscription bundle (Individuals Only)

USD  $505.00

JNS + Pediatrics + Spine - 1 year subscription bundle (Individuals Only)

USD  $600.00
Print or Print + Online

OBJECTIVE

Chiari I malformation (CM-I) has traditionally been defined by measuring the position of the cerebellar tonsils relative to the foramen magnum. The relationships of tonsillar position to clinical presentation, syringomyelia, scoliosis, and the use of posterior fossa decompression (PFD) surgery have been studied extensively and yielded inconsistent results. Obex position has been proposed as a useful adjunctive descriptor for CM-I and may be associated with clinical disease severity.

METHODS

A retrospective chart review was performed of 442 CM-I patients with MRI who presented for clinical evaluation between 2003 and 2018. Clinical and radiological variables were measured for all patients, including presence/location of headaches, Chiari Severity Index (CSI) grade, tonsil position, obex position, clival canal angle, pB-C2 distance, occipitalization of the atlas, basilar invagination, syringomyelia, syrinx diameter, scoliosis, and use of PFD. Radiological measurements were then used to predict clinical characteristics using regression and survival analyses, with performing PFD, the presence of a syrinx, and scoliosis as outcome variables.

RESULTS

Among the radiological measurements, tonsil position, obex position, and syringomyelia were each independently associated with use of PFD. Together, obex position, tonsil position, and syringomyelia (area under the curve [AUC] 89%) or obex position and tonsil position (AUC 85.4%) were more strongly associated with use of PFD than tonsil position alone (AUC 76%) (Pdiff = 3.4 × 10−6 and 6 × 10−4, respectively) but were only slightly more associated than obex position alone (AUC 82%) (Pdiff = 0.01 and 0.18, respectively). Additionally, obex position was significantly associated with occipital headaches, CSI grade, syringomyelia, and scoliosis, independent of tonsil position. Tonsil position was associated with each of these traits when analyzed alone but did not remain significantly associated with use of PFD when included in multivariate analyses with obex position.

CONCLUSIONS

Compared with tonsil position alone, obex position is more strongly associated with symptomatic CM-I, as measured by presence of a syrinx, scoliosis, or use of PFD surgery. These results support the role of obex position as a useful radiological measurement to inform the evaluation and potentially the management of CM-I.

ABBREVIATIONS AUC = area under the curve; CM-I = Chiari I malformation; CSI = Chiari Severity Index; CVJ = craniovertebral junction; PFD = posterior fossa decompression; ROC = receiver operating characteristic.

JNS + Pediatrics - 1 year subscription bundle (Individuals Only)

USD  $505.00

JNS + Pediatrics + Spine - 1 year subscription bundle (Individuals Only)

USD  $600.00

Contributor Notes

Correspondence Gabe Haller: Washington University School of Medicine, St. Louis, MO. ghaller@wustl.edu.

INCLUDE WHEN CITING Published online April 10, 2020; DOI: 10.3171/2020.2.PEDS19486.

Disclosures Dr. Limbrick reports receiving support of non–study-related clinical or research efforts that he oversees from Medtronic, Inc., and Microbot Medical, Inc.

  • 1

    Tubbs RS, Oakes WJ, eds. The Chiari Malformations. Springer Science+Business Media; 2013

  • 2

    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(6):10331036.

    • Search Google Scholar
    • Export Citation
  • 3

    Barkovich AJ, Wippold FJ, Sherman JL, Citrin CM. Significance of cerebellar tonsillar position on MR. AJNR Am J Neuroradiol. 1986;7(5):795799.

    • Search Google Scholar
    • Export Citation
  • 4

    Brockmeyer DL, Spader HS. Complex Chiari malformations in children: diagnosis and management. Neurosurg Clin N Am. 2015;26(4):555560.

    • Search Google Scholar
    • Export Citation
  • 5

    Godzik J, Dardas A, Kelly MP, Comparison of spinal deformity in children with Chiari I malformation with and without syringomyelia: matched cohort study. Eur Spine J. 2016;25(2):619626.

    • Search Google Scholar
    • Export Citation
  • 6

    Godzik J, Kelly MP, Radmanesh A, Relationship of syrinx size and tonsillar descent to spinal deformity in Chiari malformation Type I with associated syringomyelia. J Neurosurg Pediatr. 2014;13(4):368374.

    • Search Google Scholar
    • Export Citation
  • 7

    Greenberg JK, Yarbrough CK, Radmanesh A, The Chiari Severity Index: a preoperative grading system for Chiari malformation type 1. Neurosurgery. 2015;76(3):279285.

    • Search Google Scholar
    • Export Citation
  • 8

    Hekman KE, Aliaga L, Straus D, Positive and negative predictors for good outcome after decompressive surgery for Chiari malformation type 1 as scored on the Chicago Chiari Outcome Scale. Neurol Res. 2012;34(7):694700.

    • Search Google Scholar
    • Export Citation
  • 9

    Khalsa SSS, Geh N, Martin BA, Morphometric and volumetric comparison of 102 children with symptomatic and asymptomatic Chiari malformation Type I. J Neurosurg Pediatr. 2018;21(1):6571.

    • Search Google Scholar
    • Export Citation
  • 10

    Ladner TR, Dewan MC, Day MA, Posterior odontoid process angulation in pediatric Chiari I malformation: an MRI morphometric external validation study. J Neurosurg Pediatr. 2015;16(2):138145.

    • Search Google Scholar
    • Export Citation
  • 11

    Smith BW, Strahle J, Bapuraj JR, Distribution of cerebellar tonsil position: implications for understanding Chiari malformation. J Neurosurg. 2013;119(3):812819.

    • Search Google Scholar
    • Export Citation
  • 12

    Stovner LJ, Rinck P. Syringomyelia in Chiari malformation: relation to extent of cerebellar tissue herniation. Neurosurgery. 1992;31(5):913917.

    • Search Google Scholar
    • Export Citation
  • 13

    Strahle J, Muraszko KM, Kapurch J, Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging. J Neurosurg Pediatr. 2011;8(2):205213.

    • Search Google Scholar
    • Export Citation
  • 14

    Strahle J, Smith BW, Martinez M, The association between Chiari malformation Type I, spinal syrinx, and scoliosis. J Neurosurg Pediatr. 2015;15(6):607611.

    • Search Google Scholar
    • Export Citation
  • 15

    Thakar S, Sivaraju L, Jacob KS, A points-based algorithm for prognosticating clinical outcome of Chiari malformation Type I with syringomyelia: results from a predictive model analysis of 82 surgically managed adult patients. J Neurosurg Spine. 2018;28(1):2332.

    • Search Google Scholar
    • Export Citation
  • 16

    Tubbs RS, Iskandar BJ, Bartolucci AA, Oakes WJ. A critical analysis of the Chiari 1.5 malformation. J Neurosurg. 2004;101(2)(suppl):179183.

    • Search Google Scholar
    • Export Citation
  • 17

    Mariwalla NR, Boydston WR, Chern JJ. Newer subsets: Chiari 0 and Chiari 1.5 malformations. In: Tubbs RS, Oakes WJ, eds. The Chiari Malformations. Springer Science+Business Media; 2013:241246.

    • Search Google Scholar
    • Export Citation
  • 18

    Smoker WR, Khanna G. Imaging the craniocervical junction. Childs Nerv Syst. 2008;24(10):11231145.

  • 19

    Bollo RJ, Riva-Cambrin J, Brockmeyer MM, Brockmeyer DL. Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion. J Neurosurg Pediatr. 2012;10(2):134141.

    • Search Google Scholar
    • Export Citation
  • 20

    Tubbs RS, McGirt MJ, Oakes WJ. Surgical experience in 130 pediatric patients with Chiari I malformations. J Neurosurg. 2003;99(2):291296.

    • Search Google Scholar
    • Export Citation
  • 21

    Chiapparini L, Saletti V, Solero CL, Neuroradiological diagnosis of Chiari malformations. Neurol Sci. 2011;32(suppl 3):S283S286.

  • 22

    Heiss JD. Epidemiology of the Chiari I malformation. In: Tubbs RS, Oakes WJ, eds. The Chiari Malformations. Springer Science+Business Media; 2013:8392.

    • Search Google Scholar
    • Export Citation
  • 23

    Tubbs RS, Wellons JC III, Blount JP, Inclination of the odontoid process in the pediatric Chiari I malformation. J Neurosurg. 2003;98(1)(suppl):4349.

    • Search Google Scholar
    • Export Citation
  • 24

    Tubbs RS, Oakes WJ. Introduction and classification of the Chiari malformations. In: Tubbs RS, and Oakes WJ, eds. The Chiari Malformations. Springer Science+Business Media; 2013:13.

    • Search Google Scholar
    • Export Citation

Metrics

All Time Past Year Past 30 Days
Abstract Views 142 142 78
Full Text Views 66 66 36
PDF Downloads 42 42 17
EPUB Downloads 0 0 0