<prompt> Cause of unilateral secretory otitis media in an adult isCSOMNasopharyngeal carcinomaMastoiditisForeign body of external ear  <response>: Benign and malignant tumours of nasopharynx should always be excluded in unilateral serous otitis media in an adult. Nasopharyngeal carcinoma Clinical features Nasal: Nasal obstruction, nasal discharge, denasal speech and epistaxis. Otalgic: Due to obstruction of the eustachian tube, there is a conductive type of hearing loss, serous or suppoive otitis media. Tinnitus and dizziness may occur. Presence of unilateral serous otitis media in an adult should raise suspicion of nasopharyngeal growth. Ophthalmoneurologic: Squint and DiplopiaCN 6, Ophthalmoplegia CN 3,4 and 6 facial pain and reduction of corneal reflexCN 5, exophthalmos and blindnessCN 2.Involvement of CN 9,10,11 may occur constituting jugular foramen syndrome. Involvement of the cervical sympathetic chain causes horners syndrome. Cervical nodal metastasis. Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 284,285 