Transsphenoidal surgery for Cushing's disease: outcome in patients with a normal magnetic resonance imaging scan.

OBJECTIVE: Transsphenoidal surgery for Cushing's disease from a pituitary adenoma is an effective and safe treatment. Definitive preoperative diagnosis of Cushing's disease caused by a pituitary adenoma is often difficult, particularly in patients with normal imaging studies and a normal sella turcica. We present the outcome of transsphenoidal surgery in patients with presumed Cushing's disease and a normal pituitary magnetic resonance imaging scan. METHODS: Between January 1992 and December 1997, 105 patients underwent transsphenoidal surgery for Cushing's disease at our institution. The criteria for inclusion in this study were clinical and biochemical studies strongly suggestive of Cushing's disease, a normal magnetic resonance imaging scan with normal sella and sellar contents, no previous pituitary surgery, and transsphenoidal surgery performed at this institution. Eighteen patients fulfilled these criteria, and their results were analyzed retrospectively. RESULTS: The average age of the patients was 47.8 years; there were 13 women and 5 men. Inferior petrosal sinus sampling with and without corticotropin-releasing hormone stimulation was performed in 16 patients with correct localization of the lesion in 13 (81%). During surgery, the surgeon identified and removed 17 pituitary tumors; 15 patients had selective adenomectomies, one had a hemihypophysectomy, and two had total hypophysectomies. Thirteen discrete adrenocorticotropic hormone-secreting adenomas were proven histologically, and one pituitary gland had diffuse involvement with tumor. Complications occurred in five patients. Sixteen patients who were followed up for an average of 21.6 months had sustained remission, 12 of whom were profoundly hypocortisolemic immediately after surgery. CONCLUSION: In patients with Cushing's disease and a normal magnetic resonance imaging scan, an experienced surgeon can perform transsphenoidal surgery resulting in effective removal of very small microadenomas, with clinical and biochemical remission in the majority. Inferior petrosal sinus sampling is helpful in localizing the adenoma.