The nose is made up of a fixed and rigid part that is called nasal pyramid, although it rather has the shape of a tent or roof, and a pliable mobile part which is the nasal tip, the alae and its annexes. The nasal pyramid is formed by two types of structures or tissues; in the most cephalic or upper part the nasal pyramid is formed by the nasal bones and the ascending process of the maxilla, that is, by bone tissue; the most caudal or lower part of the nasal pyramid is formed by the triangular cartilages or also called quadrangular or lateral or upper lateral, that is, by cartilaginous tissue.
Both halves or walls of the nasal pyramid join and fuse horizontally with each other in the center of the nose to form the dorsum, hump or nasal bridge (misnamed by many people as the septum, which is not part of the nasal dorsum), creating what is called pyramid or bony or osseous or hard dorsum (cephalic or upper), formed by synostosis or fusion between bones, and the cartilaginous middle vault or soft pyramid or dorsum (caudal or lower), formed by synchondrosis or fusion between cartilages. In turn, the nasal dorsum is joined and merged by its lower or posterior face with the nasal septum, nasal septum which also, in turn, consists of a cephalic or upper bony part and a caudal or lower cartilaginous part, corresponding the bony septum to the fusion with the cephalic or upper or bony dorsum and the cartilaginous septum to the fusion with the caudal or lower or cartilaginous dorsum, forming a tripod in which the lateral legs are the nasal wall and the central leg the nasal septum.
Over resection of the cephalic or upper dorsal septum is one of the most common and problematic deformities in revision rhinoplasties, due to over correction during hump shaving maneuvers, either entirely and homogeneously (straight fashion) or unevenly scooped (angled or V fashion), leading to a typical sunken radix.
It may be also a consequence of a congenitally conditioned peculiar anatomy, leading to an apparently but fake prominent forehead and frontal sinus and an aggravated nasal hump.
Very specific custom structure rhinoplasty techniques have to be applied to correct such effect, aiming to fill the missing portion of the dorsum and raise the bridge to a point of suitable balance with the forehead, combining dorsum onlay grafting, rib grafting, temporalis fascia graft, etc.