The infraorbital vein: embryology, anatomy, histology, variations, and clinical relevance.

The infraorbital vein (IOV) is a small but clinically important component of the deep midfacial venous system, linking the infraorbital region, orbit, and infratemporal fossa. Despite its close association with the infraorbital nerve and artery, the IOV remains inconsistently described and systematically undercharacterized in the literature. This narrative review synthesizes current evidence on the embryology, anatomy, variations, and clinical relevance of the IOV to provide a clinically oriented framework. Embryologically, the IOV derives primarily from the primitive maxillary vein, with variable contributions from the orbitonasal venous channels, which explains its dual connections to the pterygoid venous plexus and the orbital venous system. Anatomically, it demonstrates considerable variability in presence, caliber, and spatial relationship within the infraorbital canal. The IOV may present as a single trunk, duplicated channels, or a plexiform network, with additional variation associated with accessory infraorbital foramina and emissary connections. Clinically, the IOV is relevant to orbital floor and zygomatic fracture repair, implant surgery, the spread of odontogenic infection, and esthetic procedures. Although often overlooked, the IOV represents a key component of a dynamic midface-orbit-skull base venous axis. Improved understanding of its anatomy and variation is essential for surgical planning and complication avoidance.