The value of immediate postoperative MR imaging following endoscopic endonasal pituitary surgery.

Background: Although the value of early MR imaging has been justified for microscopic transphenoidal surgery, there is no literature evaluating immediate postoperative MR imaging following endoscopic endonasal resection of pituitary adenomas. We hypothesized that MRI of the pituitary gland performed on the first postoperative day is just as effective at detecting residual disease and/or reconstruction materials as the MRI at 3 months following surgery.

Methods: We retrospectively evaluated 102 consecutive patients who underwent endoscopic endonasal surgery for presumed pituitary adenomas. Sixty-four patients met the inclusion criteria with immediate and 3 months MR imaging. Imaging was evaluated by two sets of observers. The following parameters were assessed: enhancement pattern of the pituitary gland, pituitary stalk, nodular enhancement (residual tumor) or linear enhancement (non-tumoral) and residual reconstruction/packing materials.

Results: Gross total resection of the tumors with no cavernous sinus involvement was achieved in 49 out of 52 (94%) patients. Eleven out of 12 remaining patients with cavernous sinus invasion had residual cavernous sinus component visible on both immediate and 3 month MR imaging. The pituitary gland, position of stalk, and nasoseptal flap could be identified on both post-operative MRIs in all patients. The sensitivity and specificity for residual tumor detection on immediate MRI was 100% and 97.9%, respectively. The kappa index evaluating interobserver agreement for identification of residual tumor and packing/reconstruction material on immediate MR was 0.83 and 0.72 indicating near perfect and substantial agreement, respectively.

Conclusion: Immediate MR imaging performed following endoscopic endonasal resection of pituitary lesions provides accurate and reliable information regarding the presence of residual tumor compared to reconstruction and packing materials.