Cranial Aperture of the Optic Canal in Chiari Malformation Type 2: A Morphometric Study on CT Images

To identify morphological differences in the cranial aperture (CA) of the optic canal (OC) in patients with Chiari malformation type 2 (CMT2) by comparing them with healthy individuals.

Computed tomography images were analyzed for 40 patients with CMT2 (16 females, 24 males; mean age, 10.05 ± 4.51 years; age range, 6?18 years) and 40 control subjects (21 females, 19 males; mean age, 10.03 ± 4.81 years; age range, 6?18 years). Measurements included the height (HCA), width (WCA), and surface area (ACA) of the CA, as well as the distances from the CA to the anterior border of the anterior cranial fossa (AB-CA), lateral border (LB-CA), and midsagittal line (MSLCA). Additionally, the angles of the OC were assessed in both the axial (APA) and sagittal planes (SPA).

In the CMT2 group, mean values were as follows: HCA 3.64 ± 0.81 mm, WCA 3.08 ± 0.87 mm, ACA 7.58 ± 2.84 mm2, AB-CA 44.99 ± 7.69 mm, LB-CA 29.17 ± 5.03 mm, MSL-CA 7.07 ± 2.44 mm, APA 30.64° ± 6.03°, and SPA 24.31° ± 5.09°. In the control group, corresponding values were HCA 4.22 ± 0.60 mm, WCA 4.54 ± 1.04 mm, ACA 12.81 ± 3.80 mm2, AB-CA 52.73 ± 6.71 mm, LB-CA 35.86 ± 4.33 mm, MSL-CA 10.21 ± 2.21 mm, APA 35.96° ± 3.23°, and SPA 28.64° ± 4.34°. All measurements were significantly smaller in the CMT2 group compared to controls (p < 0.001).

Patients with CMT2 exhibit significantly reduced CA dimensions and angular measurements of the OC. These differences, particularly in depth and orientation, may be clinically relevant when planning surgical interventions such as OC decompression.