Predicting the Probability of Diaphragmatic Descent with Very Large Pituitary Adenomas

Transsphenoidal surgery has eclipsed open transcranial surgery as the preferred operative management of very large pituitary adenomas, although for some tumors with significant suprasellar components, craniotomy still may be considered. Surgical decision-making is typically predicated on which approach will best decompress the optic apparatus, which from an endonasal approach, translates into predicting the likelihood of diaphragmatic descent. In this study, we aimed to identify which pre-operative neuroimaging features predict failure of intra-operative diaphragmatic descent.

A retrospective study was done of consecutive patients undergoing endoscopic endonasal surgery for pituitary adenomas 30 mm and larger by a single neurosurgeon at the UCLA Medical Center between May 2008 and April 2016 (n = 109). We correlated visualization of intra-operative diaphragmatic descent with pre-operative MRI findings as well as post hoc variables.

The probability of diaphragma descent curve intersected the 50th-ile at 20 mm for suprasellar extension (p < 0.001) and 5 mm for anterior fossa (pre-tuberculum) extension (p = 0.004). A dumbbell ratio of > 1 (p = 0.043) and extradiaphragmatic (subarachnoid) extension were predictive (p < 0.001) as well. Apoplexy and maximum tumor size were not predictive (p > 0.05). Tumor firmness, a factor that could not be identified pre-operatively, was also associated with a lower diaphragma drop rate (p < 0.001). Intraoperative CSF leak did not have an effect (p > 0.05).

Pituitary adenomas with suprasellar extension > 20 mm have a significantly lower probability of achieving chiasmal decompression via an endoscopic endonasal approach. The combination of anterior fossa extension, dumbbell shape, and subarachnoid involvement further decreases the probability. This assessment could be helpful in counseling patients pre-operatively on surgical expectations as well as surgical options.