Nontraumatic prolapse of the orbital contents into the ethmoid sinus: evaluation with screening sinus CT

The purpose of this study is to evaluate the incidence and CT features of nontraumatic prolapse of the orbital content into the ethmoid sinus, which may be a cause of orbital complication of ethmoidectomy.

CT of 1,024 consecutive patients with subjective sinonasal symptoms who underwent screening sinus CT were reviewed and analyzed. The 573 men and 451 women were between the ages of 5 and 79 years old. The patients with a history of sinus surgery of facial trauma were excluded from this study. The incidence and CT features of dehiscence and/or bowing of the lamina papyracea with prolapse of the orbital content in each age group and differences between the age groups were analyzed.

Ethmoidal prolapse of the orbital content was found in 67 patients (6.5%). There was a tendency of increasing incidence with increasing age. The incidence in the juvenile age group was significantly low (1.9%) as compared with that of adult. Four patients (0.4%) had bilateral lesions. Twenty-nine lesions showed prolapse of moderate to severe degree, and deformity of the medial rectus muscle on coronal CT image was associated in 21 lesions. Inflammatory change of adjacent ethmoid sinus was indicated in 19 lesions, and there was no statistical difference in incidence from that of the opposite side.

The incidence of nontraumatic prolapse of the orbital content is far beyond general expectations, and detailed structural information with CT for this anatomic alteration may be important before endoscopic sinus surgery to avoid possible complication. The higher incidence in adult may suggest age-related acquired etiologic factors besides congenital dehiscence or weakness of the lamina papyracea.