Stereotactic radiosurgery for patients with ACTH-producing pituitary adenomas after prior adrenalectomy

Nelson syndrome: comprehensive review of pathophysiology, diagnosis, and management

Nelson syndrome (NS) is a rare clinical manifestation of an enlarging pituitary adenoma that can occur following bilateral adrenal gland removal performed for the treatment of Cushing disease. It is characterized by excess adreno-corticotropin secretion and hyperpigmentation of the skin and mucus membranes. The authors present a comprehensive review of the pathophysiology, diagnosis, and management of NS. Corticotroph adenomas in NS remain challenging tumors that can lead to significant rates of morbidity and mortality. A better understanding of the natural history of NS, advances in neurophysiology and neuroimaging, and growing experience with surgical intervention and radiation have expanded the repertoire of treatments. Currently available treatments include surgical, radiation, and medical therapy. Although the primary treatment for each tumor type may vary, it is important to consider all of the available options and select the one that is most appropriate for the individual case, particularly in cases of lesions resistant to intervention.

Stereotactic radiosurgery for Cushing disease

The most common cause of Cushing syndrome is Cushing disease, in which hypercortisolism is produced by a functional adrenocorticotropic hormone–producing adenoma of the anterior pituitary gland. The common therapies available include microsurgical resection, conventional fractionated radiotherapy, and stereotactic radiosurgery (SRS). In this article the authors review the indications, results, and complications associated with SRS in the treatment of Cushing disease.

In as many as 90% of patients SRS results in disease remission, which is defined as a normal 24-hour urinary free cortisol level and a normal or subnormal morning serum cortisol level. Although in most patients who are subsequently cured a marked decrease in the serum cortisol level is demonstrated within 3 months after treatment, a biochemical cure may be delayed up to 3 years in some cases. Complications following SRS for pituitary adenomas are uncommon, particularly in patients with microadenomas, which are most commonly seen in Cushing disease. The most common complication is hypopituitarism, which occurs in up to 50% of patients with a mean latency period of 5 years. Radiation-induced optic neuropathy has been reported in less than 2% of cases and induction of a secondary neoplasm in less than 1% of cases.

For patients with Cushing disease, the rate of endocrinological cure following SRS appears to be similar to that attained using microsurgical resection. In contrast to surgery, SRS has the benefit of being noninvasive and associated with a very low incidence of diabetes insipidus, although hypopituitarism may be more common with SRS. With continued follow-up patient reviews and additional experience with SRS, it may become possible to make more definitive statements regarding SRS as the initial treatment for patients with Cushing disease.

Stereotactic radiosurgery for pituitary tumors

Pituitary adenomas frequently pose challenging clinical problems. Stereotactic radiosurgery (SRS) is one treatment option in selected patients. The purpose of this report is to identify the advantages and disadvantages of radiosurgery in cases of pituitary tumors to assess better its role in relation to other treatment. Methods for optimizing outcome are described. The author reviews several recent series to determine rates of growth control, endocrine response, and complications. In general, growth control is excellent, complications are very low, and reduction of excessive hormone secretion is fair. Depending on the clinical situation, SRS may be the treatment of choice in selected patients.