Dynamic proptosis.

Dynamic proptosis can be defined as exophthalmos occurring when a variable force is applied to the orbital contents. In a series of 26 patients (13 males and 13 females, 1 to 82 years old), the causes of dynamic proptosis included neurofibromatosis (nine cases), fistulas (three cases), malignancies (three cases), meningoencephaloceles (two cases), mucoceles (two cases), surgery (two cases), orbital varix (two cases), dermoid cysts (two cases), and aneurysm (one case). Dynamic proptosis can be either spontaneous or induced, and can occur either with an intact or an incompetent bony orbit.