Keywords: Pneumosinus dilatans, aerocele, pneumocele and sinus ectasia

Abstract: The precise etiology and pathogenesis of Pneumosinus dilatans remain obscure and only few cases of Pneumosinus dilatans are described in the literature. Two cases of Pneumosinus dilatans of paranasal sinuses are presented. The postulated mechanism of air trapping in the sinus cavity was logical in the first case, so surgically decompressing the sinus to overcome this valve mechanism was performed through an enlargement of maxillary ostium. The drainage of mucocele seems to be the pathogenic mechanism in the other case and observation was carried out in this case. In the following up these patients have been asymptomatic. Therefore, the etiology of Pneumosinus dilatans seems to be variable and the treatment need to be individualized.