CT of posttraumatic intradiploic pseudomeningocele of the skull base: a case report.

A 36-year-old woman presented with a 1-year history of headaches and increasing retroorbital pain on the right. Contrast-enhanced CT in axial and coronal planes showed a large low-density lesion in the skull base on the right (Figs. 1 A-1 C). This appeared as an expansile intradiploic cavity within the greater wing and body of the sphenoid, clivus, and right side of the sphenoidal sinus, with erosion of the anterior clinoid process and extension into the pterygoid process and the lateral orbital wall. A discontinuity in the medial part of the inner table of the floor of the middle fossa could be identified. The preoperative diagnosis was probable mucocele of the sphenoidal sinus. A transnasal sphenoidotomy was performed , resulting in a copious flow of CSF. Packing material was placed in the upper nasal cavity and no further intervention was attempted. Repeat cranial CT showed pneumocephalus , and the patient's headaches became more severe. Transnasal packing of the sphenoid cavity failed to stop the CSF leak. Postoperatively, a meningitis developed, which was treated with appropriate antibiotics, but the CSF rhinorrhea continued. With close questioning, additional history of severe head trauma at age 5 (fall out of a moving vehicle) was obtained. Nine weeks after her first admission , the patient underwent a right temporal craniotomy. In the medial part of the floor of the right middle fossa, the dura was dehiscent over an area considerably larger than the bone defect apparent on CT. There was no herniation of brain through the defect. A free graft of pericranium was harvested and sutured over the dural defect to create a water-tight closure. An exploration of the lateral part of the cavity , in the orbital wall , was also performed; no tumor was found , but a biopsy of the lining of the cavity wall was done. Postoperatively, CSF rhinorrhea ceased, but it recurred several weeks later, at which time the patient was referred to another institution. The skull base defect was closed from an extracranial approach, using the posterior half of the temporalis muscle . One year after initial presentation, intermittent headaches persisted, but CSF rhinorrhea has not recurred . Follow-up CT showed nearly complete obliteration of the intradiploic cavity with fatj muscle density . Microscopic examination of the lining of the cavity wall showed a nonspecific fibrous-appearing matrix, with no evidence of atypia or mitotic activi ty (Fig . 1 D). Immunohistochemical stains (S-1 00, NSE) for neural elements were negative. Vimentin stain was positive, indicating cells of meningothelial origin .