A 45-year-old man is admitted to the hospital with breathing problems. During physical examination the patient shows signs of airway obstruction. A CT scan examination reveals a nasal polyp obstructing the airway. Drainage from which of the following structures is also obstructed?

(b) Source: GAS 797, 879, 1018, 1020, 1022; GA 487, 518, 525 The nasal polyp also involved the maxillary sinus, located immediately laterally to the nasal cavity. The sphenoid sinus, located posterosuperiorly to the nasopharynx, is unlikely to be affected by a nasal polyp. The ethmoidal sinuses, located medially to the orbit and lateral to the nasal cavity, are also unlikely to be affected by a nasal polyp, although this possibility cannot be ruled out. The frontal sinuses located superomedially to the eyes are unlikely to be affected by the nasal polyp. The frontonasal ducts, the communication between the frontal sinus and the nasal cavity, are also unlikely to be affected.