nasion

The nasion is the anterior midpoint of the frontonasal suture, the junction where the frontal bone meets the two nasal bones at the root of the nose. It is a midline craniofacial point located at the bridge of the nose, just beneath the glabella.

In clinical anatomy and imaging, nasion is a primary cephalometric landmark used as a reference in radiographs and 3D scans. It serves as the origin for various measurements and for anchoring other landmarks, such as points in the midface and mandible. In orthodontics and craniofacial surgery, nasion helps describe the position of the maxilla and the midface and guides treatment planning. In anthropology and forensic science, it provides a standardized midline reference for craniofacial measurements across individuals and populations.

Definitions of nasion can differ slightly: most commonly it is the midpoint of the frontonasal suture, but some radiographic definitions take nasion as the deepest or most anterior point of the suture. For this reason, cephalometric analyses may specify the nasion definition used. The position of nasion changes with growth and can be affected by surgical modification or congenital anomalies, though it remains a stable midline reference in adulthood.

Etymology: from Latin nasus meaning nose; the term was adopted into anatomical nomenclature to designate this craniofacial landmark.