Mastoid Cyst in a Child.

Mastoid cysts are a rare condition that occurs either congenitally or secondary to chronic otological diseases with poor ventilation of the middle ear and mastoid cavity. In this presenting case, the authors report a case of secondary mastoid cyst with evidence of bony destruction and fistulous tract formation into adjacent structures. Concurrently, we reviewed other similar cases reported in the literature. A 12-year-old Malay boy with partially controlled allergic rhinitis presented with right-sided postauricular swelling and intermittent fever for three months. Examination revealed a non-tender bony swelling over the mastoid area. High-resolution computed tomography of the temporal bone revealed a large bony lytic lesion at the inferior aspect of the mastoid bone. Multidirectional fistulous tracts towards the splenius capitis muscle were seen extending from the lesion. Right mastoid exploration was done and revealed an infected mastoid cyst. Complete removal of the cyst wall and saucerization of the mastoid cavity were performed. Our patient showcases the potential of mastoid cysts to cause bony erosion, fistulation and abscess formation. Complete removal of mastoid cysts is therefore advocated to prevent its potential complications and unwarranted recurrence.