Mastoid Abscess in a Child With Eustachian Tube Dermoid Cyst.

A dermoid cyst (DC) is a benign tumor caused by inclusion errors during embryogenesis. DC of the head and neck is a well-recognized entity both clinically and histologically; however, it rarely occurs in the Eustachian tube (ET). Due to its anatomical position, significant morbidity related to middle ear dysfunction may result from ET obstruction. In this report, we present a rare case of a girl child aged two years and nine months with persistent otorrhea, who was initially diagnosed with acute otitis media with mastoiditis, along with suspicion of congenital cholesteatoma. However, high-resolution CT (HRCT) temporal and MRI of the neck revealed a DC of the ET causing left chronic otitis media (COM) with mastoid abscess. The patient underwent mastoid exploration surgery and myringotomy with grommet insertion. Although complete excision is the standard treatment modality for DC, the treatment of poorly ventilated mastoid and middle ear takes precedence over it. MRI surveillance scan is recommended in such cases.