Frontal and sphenoid sinus aplasia | Absence of bone pneumatisation |
Frontal sinus hypoplasia | Oval-shaped sinus, presence of lateral margin of the sinus medially to a vertical line drawn through the medial surface of the globe, and absence of intrasinus septa |
Sphenoid sinus hypoplasia | Oval-shaped sinus, pneumatisation limited to the pre-sphenoid, anterior to the vertical plane of the tuberculum sellae and absence of intrasinus septa |
Maxillary sinus hypoplasia | Presence of three of the following four criteria: 1) oval-shaped sinus; 2) absence of pneumatisation of the sinus below the level of the nasal floor; 3) presence of medial wall of the sinus laterally to a vertical line drawn tangentially to the medial orbital border; 4) lateral extension of the sinus medial to a vertical line drawn through the middle of the orbit at the level of the infundibulum in the coronal plane |