A 39-year-old woman has been bothered by headache, facial pressure, nasal obstruction with discharge, and diminished taste sensation for the past 6 months. On physical examination there is discomfort on palpation over her left maxillary sinus. No oral lesions are noted. Rhinoscopy shows nasal erythema, marked edema, and purulent discharge. Which of the following complications is most likely to occur in this patient?