Anatomical observations of the foramina transversaria.

Four hundred and eighty foramina transversaria in dry cervical vertebrae of 36 spines and in a number of dissections were studied and classified according to size, shape, and direction of their main diameter. A coefficient of roundness was then elaborated. The variations of foramina appear to follow a pattern at various vertebral levels. The possible factors (in addition to the embryological ones) involved in causing these variations-for example, mechanical stress, size, course, and number of vertebral vessels-were analysed. The importance of the correct interpretation of the variations in the foramina transversaria in radiographic or computerised axial tomography is discussed. The contribution of the present study to the understanding and diagnosis of pathological conditions related to the vertebral artery and its sympathetic plexus is stressed.