Background: The sphenopalatine artery which supplies most of the blood to the nasal mucosa is encased in the sphenopalastine foramen [SPF]. Knowing the location of the SPF is mendatory in sinonasal surgery in order to control posterior epistaxis and to avoid iatrogenic injury of the vessel.
Objective: To determine the location and morphometric evaluation of the SPF in its relation to surrounding anatomical
landmarks.
Materials and Methods: The lateral nasal wall of 66 embalmed half-headed Thai cadavers 20 years of age at death were dissected to expose the SPF and nearby structures. The mean diameters and distances between the SPF and fixed anatomical landmarks on the lateral nasal wall were determined-i.e. the horizontal ground lamella of the middle turbinate [HGLMT], the natural ostium and roof of the maxillary sinus, and the opening of the Eustachian tube.
Results: The respective mean vertical and horizontal diameter of the SPF was 6.1 and 4.9 mm. The SPF is situated anterosuperiorly to the posterior end of the middle turbinate. The 71.2% of the foramina were located above the attachment of the HGLMT (i.e., opened into the superior meatus) while the other 28.8% overrode the level of the HGLMT attachment (i.e., opened into the superior and middle meati). The respective mean distances from the SPF to the HGLMT, the natural ostium of the maxillary sinus, the opening of the Eustachian tube, and the roof of the maxillary sinus was 5.6, 18.1, 18.9 and 11.8 mm
Conclusion: The location of the SPF is mostly above the attachment of the horizontal ground lamella of the middle turbinate and anterosuperiorly to the posterior end of the middle turbinate. Surgeons who treat posterior epistaxis should observe above the HGLMT to find the artery leading into the SPF. Surgical procedures around the natural ostium of the maxillary sinus may lead to bleeding from the sphenopalatine artery; particularly, when extending close to the posterior wall of the maxillary sinus at the level of upper 1/3 and lower 2/3 junction of the height of the sinus.

Keywords: Sphenopalatine foramen, Sphenopalatine artery, Epistaxis, Ground lamella of middle turbinate