This sex-linked difference in anatomical variations may be correlated to the well-known sex-linked difference in aneurysm distribution.

The dimensions of the 10 triangles around the cavernous sinus were measured to define the anatomical characteristics of the triangles and to compare their consistency in shape and area. Twelve tissue blocks containing the bilateral cavernous sinuses and medial two-thirds of the middle cranial fossae were obtained from Japanese adults at autopsy, fixed to a stereotactic frame, and examined with an operative microscope. The dimensions of each triangle were measured with calipers and compared, based on the same point and border. The anteromedial triangle and the superolateral (Parkinson's) triangle were more consistent in shape than the paramedial and oculomotor triangles, but the oculomotor triangle was larger in area than these other triangles. The posteromedial (Kawase's) triangle was more consistent in shape and larger than the anterolateral, lateral, and the posterolateral (Glasscock's) triangles. The anteromedial and superolateral (Parkinson's) triangles are important for the combined epi- and subdural approach to cavernous sinus lesions. The posteromedial (Kawase's) triangle is important for gaining access to the posterior cranial fossa from the middle cranial fossa.

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Chordomas are most commonly located in the extradural region. A 56-year-old man presented with a large chondroid chordoma located totally within the intradural retroclival region. The tumor was resected via the petrosal approach. Five years after subtotal removal, the residual tumor showed no sign of regrowth despite the fact that radiation therapy had not been used. The patient was free of symptoms except for moderate, conductive hearing loss in his right ear. The position of the intradural tumor could be preoperatively diagnosed by neuroimaging and, thus, the petrosal approach was selected. Primary intradural extraosseous chordomas are very rare and difficult to differentiate from ecchordoses physaliphorae on the basis of histological and radiological features; however, MIB-1 staining may be useful.

Pituitary adenomas are usually soft, but 5-13.5% are fibrous adenomas which are difficult to remove. Magnetic resonance (MR) imaging and operative findings were evaluated in eight patients (12.1%) with fibrous pituitary adenoma among 66 patients. Tumor specimens were examined histologically and immunohistochemically for collagen content and subtypes. Seven patients had clinically inactive nonfunctioning pituitary adenomas and one patient growth hormone-secreting adenoma. All patients underwent transsphenoidal surgery. Four cases were giant adenomas with suprasellar extension of more than 2 cm. T 1 -and T 2 -weighted MR imaging showed the tumors as nearly isointense to the surrounding brain, except in one case where the tumor was high intense on T 2 -weighted MR imaging. All tumors required piecemeal resection using a micro-dissector and tumor forceps. Four tumors of maximum size more than 3 cm needed a second operation. The interface between the thinned normal pituitary gland and fibrous adenoma was intended to identify at the anterior-superior portion in recent four cases, which was helpful to remove the tumors and preserve pituitary functions. Histological examination revealed prominent deposition of collagen in the perivascular area. The percentage of collagen content in fibrous adenomas was more than 5% and significantly higher than that in soft adenomas and normal pituitary glands. Immunohistochemical examination showed positive staining for collagen types I and III in the fibrous adenomas, but only for type V collagen in the normal pituitary glands. Large fibrous adenomas can be resected by transsphenoidal surgery which may require two-stage operations. Identification of the interface between the normal pituitary gland and adenoma is helpful to remove fibrous adenomas and to preserve pituitary functions. We propose that firm adenomas containing more than 5% collagen are``fibrous'' adenomas.