Fourth branchial fistula.

The course of a fourth branchial fistula is reviewed. Although no complete fistula has yet been described, the anatomy of such a fistula can be determined from a knowledge of the embryologic development of the brachial region. The fistula must first ascend over the hypoglossal nerve before caudal to the fourth area arterial structures. This description is different from the one commonly recognized by otolaryngologists.