Measurement of the A/N ratio. B, line tangent to the straight part of the basiocciput; A’, the point of maximal convexity of the inferior part of the adenoidal shadow; A, line perpendicular to B and passing through the A’ point; D’, the anteroinferior limit of the sphenobasioccipital synchondrosis, or the intersection between the posteroinferior margin of the pterygoid plates and the inferior margin of the basiocciput; PNS, posterior nasal spine point; N, the line connecting the D’ and the PNS points.