Origin of craniopharyngiomas: implication on the growth pattern

The surgical management of craniopharyngiomas has been among the most challenging neurosurgical procedures because of their complex topographical relationship with surrounding structures and high recurrence rate after subtotal resection. Craniopharyngiomas have been classified only by their location to determine an appropriate surgical approach without due regard to other factors that could affect the surgical results, such as the extent of adhesion to surrounding structures or the nature of the tumor.

We describe the role of the diaphragm sellae on the growth patterns of craniopharyngiomas from surgical experiences and pathological evidences, suggesting the classification of craniopharyngiomas into three categories by the level of origin and the competence of the diaphragm sellae: a tumor of subdiaphragmatic origin with competent diaphragm sellae, subdiaphragmatic with incompetent diaphragm sellae, and supradiaphragmatic.

Tumors in each category have shown peculiar topographical relationship with the optic chiasm, third ventricle, and also adhesion extents. The nature of the tumor itself, e.g., the composition of cystic and solid parts, may bring additional minor variations to the topographical features of a craniopharyngioma, but will maintain the major characteristics determined by its level of origin and competence of the diaphragm sellae.

This classification scheme, which considers the origin level, is clinically relevant and useful because optimal surgical approaches could be designed by considering multiple factors affecting surgical procedure and outcome, including the expected extent of adhesion and preferred sites of recurrence, as well as the topographical location of the tumor. In subdiaphragmatic tumors, which correspond to intrasellar and prechiasmatic tumors, a transsphenoidal approach could be reasonably attempted even with considerable suprasellar extensions because they tend to adhere to the intrasellar structures, and the superior surface of the tumor may be easily separated from the brain structures by pulling. Supradiaphragmatic tumors, however, may need a wider surgical approach that can provide direct vision of the tumor because of possible extensive adhesion.