Osteologic classification of the sphenopalatine foramen.

Textbook descriptions and illustrations of the opening of the sphenopalatine foramen (SPF) into the nasal cavity place it above and behind the posterior end of the middle turbinate (i.e., within the superior meatus). Although true for some skulls, this is not the situation for the majority and may be of importance, because the major blood supply to the nasal cavity enters via this route. Having studied 238 lateral nasal walls, the authors propose a classification of the osteology of the sphenopalatine foramen. In class I (35%) the opening of the SPF is purely into the superior meatus with a notch or foramen in the middle turbinate/ethmoidal crest of the palatine bone. In class II (56%) the SPF spans the ethmoidal crest (i.e., opens into both the superior and middle meati). In class III (9%) there are two separate openings into the superior and middle meati. These findings may explain the route of the artery to the inferior turbinate and indicate the need for care in dealing with the posterior end of the middle turbinate. They may also suggest a potential site for dealing with "difficult" epistaxis via an intranasal route.