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Fetal sphenoid bone: imaging using three‐dimensional ultrasound and computed tomography

The sphenoid bone is a medial bone that contributes to the formation of the cranial, nasal and orbital cavities. It is composed of three parts, namely the body and greater and lesser wings. The body, which is more or less cuboid, is located at the base of the occipital and ethmoid bones. The lesser wings define the contour of the optical duct, and the superior smooth face of the lesser wings is in contact with the frontal bone and contributes to the formation of the anterior cranial floor and orbit. The greater wings contribute to the medial cranial floor 1 . Imaging the sphenoid bone in the human fetus can be achieved partially using two-dimensional (2D) ultrasound. In a cross-sectional study of 386 normal singleton fetuses at 14–40 weeks’ gestation, Deganiet al. 2 used it to measure the largest diameter of the sphenoid bone in an axial plane of the fetal brain, showing the four cranial fossae divided by the greater wings of the sphenoid anteriorly and the otic cartilage posteriorly. They reported significant positive linear relationships between sphenoid wing length and gestational age, femur length and biparietal diameter. They also reported that the sphenoid wing lengths of two microcephalic fetuses were less than 2 SD below the mean, and that the anterior cranial angles were more than 2 SD above the mean in two brachycephalic fetuses 2 . However, the position and complexity of the shape of the sphenoid bone are