Is magnetic resonance imaging useful in guiding the operative approach to large pituitary tumors?

Forty-two patients with large pituitary tumors were studied with magnetic resonance imaging scans. Based on the operative findings, the tumors were divided into two groups. Tumors in Group 1 (n = 35) were soft or partially necrotic and were easily removed by suction and curettage. Tumors in Group 2 (n = 7) were firm and required sharp dissection or use of the laser for removal. Tumors were divided into two groups based on the long TR signal: a) isointense in comparison with white matter, or b) hyperintense in comparison with white matter. All 7 firm tumors (Group 2) had an isointense signal on long TR sequences. Thirty-two of 35 soft tumors showed a hyperintense signal on long TR sequences, and 3 an isointense signal. Based on these results, we recommend a transsphenoidal approach for the initial operation in patients with large pituitary tumors. If the tumor is largely isointense on the magnetic resonance imaging scan, we discuss with the patient preoperatively the possibility (70% in this series) that the tumor may be too firm to remove in a single transsphenoidal procedure. In these circumstances, a second, transcranial, procedure may be required to decompress the suprasellar structures adequately.