Posttraumatic iatrogenic meningoencephalocele following tympanoplasty: illustrative case.

backgroundIatrogenic meningoencephalocele of the temporal bone is a complication of middle ear surgery and is typically associated with inflammation-related defects. Trauma-related iatrogenic meningoencephalocele is rare, and its pathogenesis remains poorly understood. OBSERVATIONS: A teenage girl sustained a head injury with a left temporal bone fracture that extended to the mastoid tegmen. Owing to sensorineural hearing loss and facial nerve palsy, she underwent mastoidectomy and tympanoplasty without exposure of the dura. Twelve months later, imaging revealed a meningoencephalocele herniating into the mastoidectomy cavity. Skull base reconstruction was performed via a middle cranial fossa approach. The dura beneath the fracture line had disappeared, and a bony defect of the mastoid tegmen was identified. Although the mastoid tegmen was preserved during mastoidectomy, the authors speculate that the persistent weight of the temporal lobe, acting on the tegmen after loss of postoperative support, progressively enlarged the bony and dural defects along the preexisting fracture line extending to the mastoid tegmen, ultimately resulting in a meningoencephalocele. The skull base was reconstructed using temporalis fascia, and the postoperative course was uneventful. LESSONS: Skull base fractures of the tegmen, similar to inflammation-related defects, should be recognized as a risk factor for delayed iatrogenic meningoencephalocele after mastoidectomy. https://thejns.org/doi/10.3171/CASE26160.