抄録
Thirty five cases of tumors in the pituitary region were analysed by two-plane CT (ordinary sections and reverse sections) in order to obtain a more accurate image of the tumor and thus establish an appropriate indication for the subnasal transsphenoidal approach. Ordinary sections were examined at +25° from Reid's base line and reverse sections were examined at -20° from Reid's base line by EMI 1010. The reverse section was preferable in eliminating artifacts caused by body movements, air in the sinus or tooth filling. The reverse section was also advantageous because it was almost identical to the route of the subnasal transsphenoidal approach. In some cases, the overlapping and magnification method was used in the reverse section to clearly demonstrate small lesions.
The tumors of pituitary region were classified into six groups (Types I ?? VI) according to their degree of extension and direction of growth: Type I: intrasellar tumors; Type II : tumors with extension to the chiasmatic cistern; Type III: tumors with suprasellar extension compressing the third ventricle up to the foramen of Monro; Type IV: tumors with suprasellar extension beyond the foramen of Monro; Type V: tumors with parasellar extension; and Type VI: huge tumors extending upward and compressing the lateral ventricle. Small tumors such as Types I and II were detected more clearly by the reverse section than by the ordinary section. In cases of large tumors (Types III ?? VI) relation of the tumor to the surrounding structures such as the sphenoid sinus, third ventricle, lateral ventricle, middle fossa and brain stem was accurately demonstrated by the reverse section. In the differential diagnosis of tumors in the pituitary region, tumors showing mixed density or slightly high density and widening of the antero-posterior diameter of the sella in the precontrast reverse section and homogeneous enhancement by infusion were likely to be pituitary adenomas. One third of the pituitary adenomas showed ring-like high density in the post-contrast reverse section. Calcification was not seen in the pituitary adenomas by CT scans. All craniopharyngiomas belonged to TypesIII ?? VI. Craniopharyngiomas showed high and/or low density, and various degrees of calcification in plain CT scans. Ring-like high density was seen in two thirds of the craniopharyngiomas. About one third of the craniopharyngiomas showed widening of the antero-posterior diameter of the sella.
The subnasal transsphenoidal approach was applied to patients with tumors of Types I ?? III, and subcapsular total removal of the tumor was successfully performed. For older or severely complicated patients with tumors of Type IV, the subnasal transsphenoidal approach was also an appropriate method to decompress the optic nerve effectively and safely.
