A case of temporal meningoencephalocele presenting with persistent otorrhea following tympanostomy tube insertion

Introduction: Meningoencephalocele is a relatively rare pathology, which is a brain herniation with the surrounding arachnoid into the extracranial space. It is more likely to occur following an ear surgery or trauma within the temporal bone. We present a case of meningoencephalocele that was found due to persistent ear discharge after tympanostomy tube insertion.<br>Case report: A 60-year-old female had undergone placement of tympanostomy tubes on both ears at another hospital 10 years previously. After the left tube had been removed due to persistent ear discharge, she moved away from the hospital. When she visited our hospital complaining of bilateral hearing loss, her left ear drum looked like otitis media with effusion. Accordingly, placement of a tympanostomy tube on the left ear was attempted again, but watery otorrhea appeared and continued after placement. CT scan and MRI revealed a middle fossa cranial defect and meningoencephalic herniation into the mastoid cavity. The transmastoid approach was selected to excise the meningoencephalocele and to control cerebrospinal fluid leakage by obliteration of abdominal fat into the mastoid cavity without a craniotomy. Histopathological findings were consistent with brain tissue. Neither meningoencephalic herniation nor cerebrospinal liquorrhea has recurred.<br>Discussion and Conclusion: Meningoencephalic herniation into the temporal bone without a history of trauma or surgery is unusual and occurs insidiously. This pathology may be found either by episodes of meningitis or conductive hearing loss due to fluid collection in the middle ear. In the latter, care must be taken regarding insertion of the tympanostomy tube and subsequent serous discharge. As a curative treatment for meningoencephalocele within the temporal bone, a transmastoid approach, middle cranial fossa approach, or a combined approach should be selected. Of these, meningoencephalic excision followed by fat obliteration via the transmastoid approach seems to be a safer and more reliable method for otologists.