Encephalocele.Temporal bone encephaloceles are rare. They may be congenital or acquired. Congenital lesions arise in tegmental tegmental /teg·men·tal/ (teg-men´t'l) pertaining to or of the nature of a tegmen or tegmentum. dehiscences, primarily at the junction of the petrous petrous /pet·rous/ (pet´rus) resembling a rock; hard; stony. pet·rous adj. 1. Of stony hardness. 2. and squamous portions of the temporal bone. Acquired encephaloceles occur as a result of chronic ear disease, aberrant arachnoid granulations, trauma, and iatrogenic causes. Patients who have a longstanding history of chronic ear disease and/or multiple surgeries for ear disease are at higher risk for developing an encephalocele or a CSF leak from the temporal bone. However, the likelihood of an encephalocele developing when intact dura is exposed during otologic surgery is low. In order for an encephalocele to develop after otologic surgery, a dural injury and subsequent brain herniation must occur. The diagnosis of encephalocele is suggested in the history and physical examination. Preoperative confirmation can be obtained by computed tomography (CT) and/or magnetic resonance imaging magnetic resonance imaging (MRI), noninvasive diagnostic technique that uses nuclear magnetic resonance to produce cross-sectional images of organs and other internal body structures. (MRI). Once the diagnosis is made, treatment is primarily surgical: transmastoid repairs for smaller, lateral lesions (<1 cm) and combined transmastoid middle fossa repairs for larger, medial lesions (> 1 cm). The herniated herniated /her·ni·at·ed/ (her´ne-at?ed) protruding like a hernia; enclosed in a hernia. her·ni·at·ed adj. brain tissue is typically nonfunctional and may be amputated; the bony cranial defect must be repaired at that time. We evaluated a 68-year-old woman who had been referred to us by another otolaryngologist for evaluation of a possible encephalocele that had been detected on otoscopy. She had a surgical history of a left-sided radical mastoidectomy for chronic ear disease more than 25 years earlier. On physical examination, we noted a large, pale mass that was well covered in squamous epithelium just medial to her external auditory meatus, which was pulsatile (figure, A). Coronal CT and MRI CT and MRI Two high technology methods of creating images of internal organs. Computerized axial tomography (CT or CAT) uses x rays, while magnetic resonance imaging (MRI) uses magnet fields and radio-frequency signals. Both construct images using a computer. (figure, B) revealed a 1.3-cm tegmen tegmen /teg·men/ (teg´men) pl. teg´mina [L.] a covering structure or roof. tegmen tym´pani defect with the encephalocele. Because the layer of tissue overlying the herniated brain was extremely thin, we performed a middle fossa craniotomy Craniotomy Definition Surgical removal of part of the skull to expose the brain. Purpose A craniotomy is the most commonly performed surgery for brain tumor removal. with reduction of the encephalocele and repair of the tegmen defect with a split calvarial bone graft. [FIGURE OMITTED] Suggested reading Sdano MT, Pensak ML. Temporal bone encephaloceles. Curr Opin Otolaryngol Head Neck Surg 2005; 13(5):287-9. Wootten CT, Kaylie DM, Warren FM, Jackson CG. Management of brain herniation and cerebrospinal fluid leak cerebrospinal fluid leak CSF leak Neurology The inappropriate loss of fluid from the otherwise sealed CSF space Etiology Trauma to head–eg CSF rhinorrhea, CSF otorrhea, cranial base surgery Diagnosis Suspicious post-op nasal or ear drainage, in revision chronic ear surgery. Laryngoscope 2005; 115(7): 1256-61. James Lin, MD; Jose N. Fayad, MD |
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