Chulalongkorn Medical Journal


Background: Syringohydromyelia occurs about 30.0 - 85.0% in patients with Chiari I malformation (CMI). The syrinx formation is supposed to be a result of disturbed cerebrospinal fluid flow dynamics, which is associated with the degree of mechanical blockage that may be related to posterior cranial fossa (PCF) and craniovertebral junction anatomy. Objective: Our study aimed to determine the morphometric difference in PCF and craniocervical junction between the CMI patients with and without syringohydromyelia. Methods: Thirty CMI patients (16 with syringohydromyelia; 14 without syringohydromyelia) and 16 healthy subjects were also recruited. PCF and craniocervical junction measurements of 5 distances and 5 angles were performed. Comparison of these measurements was employed among the three groups. Results: The clivus length and Klaus index in the CMI patients were shorter than in the controls (P = 0.002 and P < 0.001). The twining line was shorter in the CMI patients without syringohydromyelia when compared to the control (P = 0.046). The Boogard’s and Nasion-basion-Opisthion (NBO) angles were larger, and the clivus gradient angle was smaller in the CMI patients with syringohydromyelia than the controls (P = 0.009, P = 0.014, and P = 0.009). Degree of tonsillar descent, the distances and the angles were not significantly different between the CMI patients with and without syringohydromelia. Conclusion: Our study showed no difference of PCF and craniocervical junction morphometry between CMI patients with and without syringohydromyelia. The results support that CMI patients has underdeveloped PCF and more clivus horizontal orientation than the healthy subjects. Large population study with evaluation of mechanical and functional factors may help understanding and predicting the risk of syrinx formation among CMI individual.



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