Pathophysiologic Review of Blow-Out Fracture and Blow-Out Fracture Extended to Subarachnoid Space Due to Air Gun Injury.

Blow-out fracture is usually caused by direct traumatic events in the periorbital area. But in this case, the authors introduce a case in which the medial orbital wall was fractured directly through the medial rectus muscle by high pressure air gun.A 38-year-old man was injured in his right periorbital area after being hit by high pressure air gun. He had mild ecchymosis and subconjunctival hemorrhage. He had a normal light reflex and intraocular pressure of 14 mm Hg. A facial computed tomography scan confirmed a blow-out fracture of the medial orbital floor with multiple extensive subcutaneous emphysema in the right hemifacial area. Free air was also seen near the basal cistern and Sylvian fissure, indicating a pneumocephalus. The operation was performed after swelling and emphysema were subsided. Intraoperative, medial rectus muscle was damaged. After the operation, no abnormal findings were observed in the ophthalmic examination. Also, the free air findings, which were observed in preoperative x-ray, have disappeared.This case is a rare case in which an orbital wall has been fractured directly through the medial rectus muscle due to an air gun injury. Therefore, we should always kept in mind that blow-out fractures can occur even with unusual mechanisms.