Precise Localization of the Posterior Clinoid Process in the Fetal Skull Base.

Abstract

To determine the precise position of the posterior clinoid process (PCP) in fetuses. Skull bases of 32 fetuses (11 males/21 females) aged 17 to 32 weeks in utero were included in the study. The distances of PCP to certain reference points were measured. The distances of PCP to the foramen ovale, foramen rotundum, superior orbital fissure, anterior clinoid process, foramen magnum, and crista galli were measured as 7.70±1.86mm, 6.99±1.65mm, 6.07±1.85mm, 3.85±1.10mm, 15.34±3.38mm, and 14.49±2.65mm, respectively. All parameters were similar for both sides (P>0.05). Apart from the distance of PCP to the foramen magnum, the remaining parameters were similar for both genders. This parameter was greater in males than females (P=0.001). All parameters were greater in the third-trimester fetuses than the second-trimester fetuses. All parameters increased with advancing gestational weeks (P<0.001). Linear functions were calculated for the distances of PCP to the crista galli (y = 1.311 + 0.551 × age), to the foramen magnum (y = 0.086 + 0.638 × age), to the anterior clinoid process (y = -0.303 + 0.174 × age), to the superior orbital fissure (y = - 2.013 + 0.338 × age), to the foramen rotundum (y = 1.803 + 0.217 × age), and to the foramen ovale (y = 0.760 + 0.290 × age). The measured distances increased with growth. The linear functions displaying the growth dynamics of PCP-related parameters may be used to estimate the distances.