Objective: To report the first case of Nelson's syndrome due to an ectopic intracranial corticotropin-secreting tumor arising entirely within the cavernous sinus.
Methods: We present a case report of Nelson's syndrome with clinical, laboratory, and radiologic features throughout a 25-year period.
Results: A 54-year-old woman had been treated for Cushing's disease with bilateral adrenalectomy in 1971. Subsequently, Nelson's syndrome developed, and she had severe generalized hyperpigmentation and substantially increased plasma corticotropin levels. In 1976, she underwent a transsphenoidal hypophysectomy. Postoperatively, despite the development of panhypopituitarism and diabetes insipidus, she remained hyperpigmented and had persistently increased plasma corticotropin levels. Throughout the years, efforts to identify the site of the corticotropin-secreting tumor were unsuccessful until 1988, when magnetic resonance imaging revealed a mass in the right cavernous sinus; subsequently, petrosal sinus cannulation corroborated the intracavernous source of excess corticotropin. Cobalt-60 gamma knife radiotherapy in 1992 was followed by a clinical and hormonal response 4 1/2 years later.
Conclusion: This report describes only the second reported case of an intracranial corticotropin-secreting tumor arising entirely within the cavernous sinus and the first such case associated with Nelson's syndrome. Although rare, the possibility of an ectopic intracranial or extracranial pituitary adenoma should be considered in patients with pituitary hypersecretion without clear-cut intrasellar abnormalities or those with no response to surgical resection of the pituitary gland.