Microradiographic and histological study of the styloid process of the temporal bone.

In order to establish the mechanisms underlying the morphogenesis of the so-called 'elongated styloid process', a comparative microradiographic and histological study was performed on 19 long and short processes. Some morphological differences between short and long processes are noticed. Numerous partially calcified cartilaginous islets are observed within the trabecular bone of very long styloid processes or covering their tip. Calcified fibrous tissue or calcified fibrocartilage sometimes contributes to the thickening of enlarged styloid processes. But the growth of the process does not seem to be due either to calcification or to ossification of the stylohyoid ligament, as thought in the past. Mechanical stresses stretching the second branchial arch during the fetal development probably induce a variable involvement of the different parts of Reichert's cartilage in the morphogenesis of the styloid process. The so-called 'elongated styloid process' should thus be congenital. However, a further growth is still possible through the activity of the cartilaginous cap of the tip.