Patients with maxillary sinus foreign bodies are frequently encountered in the fields of otolaryngology and dental and oral surgery. In the majority of cases, the cause is iatrogenic in relation to dental care, or a result of trauma. We report a case of long-term retention of a foreign body (an arrow nock) in the maxillary sinus. A 50-year-old man was referred to our hospital by a local practitioner with suspected mycosis of the left maxillary sinus. Computed tomography showed an opacity in the maxillary sinus suggestive of a foreign body, but we misidentified it as a fungus ball. However, presence of a foreign body (an arrow nock) in the maxillary sinus was confirmed during endoscopic sinus surgery and the foreign body was removed. The patient gave a history of having sustained facial trauma during archery practice 30 years ago. We speculate that the foreign body had entered the maxillary sinus at the time of that accident. Maxillary sinus foreign bodies are usually associated with dental treatment, and finding of an arrow nock in the sinus is quite rare. Since a plastic foreign body does not elicit much antigen tissue reaction, the arrow nock had remained lodged in the sinus for a long time. This case underscores the need to bear in mind that foreign bodies can enter the sinuses at the time of facial trauma and remain lodged there for long periods of time.
