Background: Most craniopharyngiomas can be classified as either "prechiasmatic" or "retrochiasmatic" according to their growth patterns. The purpose of our study was to investigate the factors determining these growth patterns.
Methods: The radiological, operative, and pathological findings of 25 consecutive cases were reviewed.
Results: In cases with prechiasmatic growth (n = 14), most tumors were easily separated from the undersurface of the third ventricular floor with the exception of a small area at the top of the tumor where tumor-glial interfaces occurred. Pathological examination of the tough tumor surface demonstrated well-organized collagen tissue, which is compatible with diaphragm sellae. All tumors of this type had intrasellar components, suggesting a subdiaphragmatic origin for this tumor type. On the other hand, tumors with retrochiasmatic growth (n = 11) demonstrated a prefixed chiasm, and most of the surface excluding areas exposed to ventricular cerebrospinal fluid showed tumor-glial interfaces. With the exception of three, all tumors of this type lacked intrasellar components, and the diaphragm sellae was depressed and free of tumor, suggestive of a supradiaphragmatic infundibular origin of the tumor.
Conclusion: Growth pattern is closely correlated to the origin of the tumor, whether it is above or below the diaphragm sellae. In craniopharyngiomas with prechiasmatic growth, the major portion of the tumor could be resected by traction. These tumors are candidates for the transsphenoidal approach if the sphenoid sinus is pneumatized. Tumors with retrochiasmatic growth, which are not covered by diaphragm sellae and contact brain tissue directly, are easily torn by traction and the tumor-glial interface should be carefully dissected under direct vision.