Devoted to diagnostic and interventional spine imaging and therapeutics


Tapering of the central spinal canal in patients with Chiari I 2012

General Spine

Jill, A, Hammersley, M.D.
Yonker, Wang, M.D., Non ASSR Member
Alejandro, Munoz Del Rioz, Ph.D., Non ASSR Member
Victor, Haughton, M.D., Non ASSR Member



Cervical spinal canal tapering may increases CSF velocities and pressures. One report suggests that the cervical spinal canal tapers more steeply in Chiari I patients than in normal subjects. The goal of this study was to test the conclusion by measuring spinal canal tapering in another cohort of patients.

Methods & Materials

Consecutive patients with scoliosis and MR imaging were selected. The MR images were evaluated for tonsilar herniation and syringomyelia. On a midline T2 weighted MR image, the anterior-posterior diameter of the spinal canal was measured at each cervical level, and a linear trendline was fit to the them by least-squares regression. The slope of this line was recorded as the taper ratio in mm/level. Patients with more than 5 mm of tonsilar herniation (with or without syrinx) were compared to those without tonsilar herniation (with or without syrinx). Differences in taper ratios for the two groups were tested for significance by the Kruskal-Willis test with significance set at 0.05.


Fifty-four scoliotic patients were identified; 22 had a Chiari malformation and 32 did not. Syringomyelia was identified in 20 of the Chiari patients and in 8 of the others. The taper ratios averaged -0.9 mm/level for the patients with a Chiari malformation (with or without a syrinx) and -0.4 mm/level for the patients without a Chiari, significant at p = 0.035. Syringomyelia did not substantially alter the taper ratio in either group.


Scoliotic patients with a Chiari malformation have more steeply tapering cervical spinal canals than scoliotic patients without it.

References/Financial Disclosures

Shah S, Haughton V, del Río AM. AJNR Am J Neuroradiol. 2011 Jun-Jul;32(6):1149-53. Epub 2011 Apr 21.CSF flow through the upper cervical spinal canal in Chiari I malformation. Hirano M, Haughton V, Munoz del Rio A. Tapering of the Cervical Spinal Canal in patients with Chiari I malformations. Submitted for publication Tatarek, N. Variation in the human cervical neural canal. The Spine Journal 2005; 5: 623-631. Linge SO, Haughton V, Løvgren AE, Mardal KA, Helgeland A, Langtangen HP.Effect of Tonsillar Herniation on Cyclic CSF Flow Studied with Computational Flow Analysis. AJNR Am J Neuroradiol. 2011 Sep;32(8):1474-81. Epub 2011 May 19. Linge SO, Haughton V, Løvgren AE, Mardal K-A, LOangtangen HP. CSF flow dynamics at the craniovertebral junction studied with an idealized model of the subarachnoid space and computational flow analysis. AJNR Am J Neuroradiol. 2010 Jan;31(1):185-92. Epub 2009 Sep 3. Oldfield EH, Muraszko K, Shawker TH, Patronas NJ. Pathophysiology of syringomyelia associated with Chiari I malformation of the cerebellar tonsils. Implications for diagnosis and treatment. J Neurosurg. 1994 Jan;80(1):3-15. Bland, JM and Altman, DG (1986) "Statistical methods for assessing agreement between two methods of clinical measurement", Lancet, 327(8476), 307-310. 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. 1999 Oct;91(4):553-62. Nakahara D, Yonezawa I, Kobanawa K, Sakoda J, Nojiri H, Kamano S, Okuda T, Kurosawa H. Magnetic resonance imaging evaluation of patients with idiopathic scoliosis: a prospective study of four hundred seventy-two outpatients. Spine (Phila Pa 1976). 2011 Apr 1;36(7):E482-5. Inoue M, Minami S, Nakata Y, Otsuka Y, Takaso M, Kitahara H, Tokunaga M, Isobe K, Moriya H. Preoperative MRI analysis of patients with idiopathic scoliosis: a prospective study. Spine (Phila Pa 1976). 2005 Jan 1;30(1):108-14.