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An Encephalocele as a Complication of Mastoid Surgery

Figure. Good correlation between coronal CT (A) and MRI (B) of the right temporal bone demonstrates the encephalocele. CT shows the bone defect in the tegmen tympani and the nonspecific soft-tissue mass in the area of the mastoidectomy and middle ear (arrow). MRI clearly demonstrates the brain herniation (large arrow) and the surrounding CSF (small arrows) . A residual inflammatory process is also noted in the mesotympanum . Otolaryngologists have described brain herniation into the mastoid for many years. Although this condition can develop as a result of congenital defects, encephaloceles can also occur postsurgically . Advances in neuroradiology, such as computed tomography (CT) and magnetic resonance imaging (MRI), have improved the diagnosis and management of lesions that erode the tegmen tympani . I The diagnosis of brain herniation should be suspected in any patient who has a history of complicated chronic ear surgery in addition to a slowly developing pulsatile mass and cerebrospinal fluid (CSF) leak. Weevaluateda5 l -year-old man whose chief complaint was a sensation of fullness in his right ear. The patient had undergone several previous surgeries for chronic mastoiditis on the right. He also complained of chronic headaches and intermittent drainage of the right ear. CT identified a bone defect in the tegmen tympani and a softtissue mass in the area of the mastoidectomy and middle ear cavity, which was thought to represent a recurrent cholesteatoma (figure, A). MRI clearly demonstrated that the mass represented a brain herniation through the tegmen tympani (figure, B). Surgical exploration with a right temporal craniotomy was performed, and the presence of an encephalocele was confirmed. The encephalocele and the CSF leak were subsequently repaired .