eng Science and Education Publishing American Journal of Medical Case Reports 2014-11-12 2 11 256 258 10.12691/ajmcr-2-11-9 AJMCR20142119 article Asif Salimov asifselimov2003@hotmail.com 1 Serdar Ozer 1 Celil Gocer 2 Burce Mocan 3 Riza Onder Gunaydin 3 Omer Taskin Yucel 3 Hacettepe University Hospital, Department of Otolaryngology Head and Neck Surgery, Ankara, Turkey Ozel Lokman Hekim Hospital, Otolaryngology Division, Ankara, Turkey Hacettepe University Hospital, Department of Radiology, Ankara, Turkey Arachnoid cysts are benign lesions that contain content similar to cerebrospinal fluid. Arachnoid cysts may cause neurological symptoms but they are commonly asymptomatic. They are commonly located in the middle cranial fossa. Paranasal sinuses are rare locations of them. We present a case with a preoperative diagnosis dilemma about young male patient with headache, vomitting and proptosis. Cranial MR scanning showed large left temporal arachnoid cyst and other cystic lesion with different signal changes in the left sphenoid sinus which leads to enlargement of the sinus. In this article we are discussing the patient, that had cerebrospinal fluid (CSF) rinorrhea; after his left sphenoid sinus explored at outside clinic, then getting up with conservative follow-up, with radiological imagings and literature findings. We should consider arachnoid cysts within differrential diagnosis of intrasphenoidal cystic lesions. http://pubs.sciepub.com/ajmcr/2/11/9/ajmcr-2-11-9.pdf arachnoid cyst sphenoid sinus cerebrospinal fluid rinorrhea