Unilateral proptosis of unexplained origin. 3.

ORBITAL exploration has shown that the commonest causes of unilateral proptosis of unexplained origin are small cavernous haemangiomata and blood cysts in the muscle cone space not extending to the orbital apex (Mortada, 1962a). When orbital exploration reveals no abnormality but is followed by slowly progressive proptosis, repeated skull x rays usually show that the cause is a deep orbital wall bony tumour or mucocele of an accessory nasal sinus (Mortada, 1963).