Analysis of the Cranial Aperture of the Optic Canal in Patients with Chiari Type-I Malformation.

Aim: To examine the morphological properties of the cranial aperture of the optic canal (CAOC) in patients with a Chiari type-I malformation (CIM).

Material and methods: Radiological images of 40 patients with CIM (24 females/16 males, mean age: 20.75 ± 14.98 years) and 40 normal individuals (24 females/16 males, mean age: 23.13 ± 18.89 years) were included in the study to assess the anatomical features of CAOC.

Results: The CAOC width (p=0.137), CAOC height (p=0.243), distance between the CAOC and the midsagittal line (p=0.982), and angle of the optic canal in the sagittal plane (Ang-in-SP) (p=0.598) were similar in patients with CIM and in the controls. The distances between the CAOC and the anterior (Dis-to-AB) and lateral (Dis-to-LB) boundaries of the anterior skull base were smaller in patients with CIM than in the controls (p < 0.01). However, the angle of the optic canal in the axial plane (Ang-in-AP) was greater in patients with CIM than in the controls. Four different aperture shapes were identified in the CIM group (teardrop, n=42 [52.40%]; triangular, n=17 [21.30%]; oval, n=9 [11.30%]; and round, n=12 [15%]) and in the control group (teardrop, n=36 [45%]; triangular, n=14 [17.50%]; oval, n=10 [12.50%]; and round, n=20 [25%]).

Conclusion: A greater Ang-in-AP and shorter Dis-to-LB and Dis-to-AB were found in patients with CIM than in the healthy controls. The distance measurements demonstrate that patients with CIM have a shorter and narrower anterior fossa than normal individuals.