Nelson's syndrome: physiopathology, management and prognosis.

A classical description of a postadrenalectomy syndrome in Cushing's disease, described in 1958 by Don Nelson, included a deep skin hyperpigmentation, presence of a large pituitary tumor, high plasma adrenocorticotropic hormone levels and visual field deficits. The main pathophysiological mechanism of Nelson's syndrome development is a loss of feedback control of hypercortisolemia on corticotroph as a consequence of the removal of hyperactive adrenal glands. Modern techniques of imaging, computed tomography and MRI, made early detection of pituitary tumor at the stage of microadenoma possible. Determinations of plasma adrenocorticotropic hormone concentration during replacement therapy are the next essential diagnostic element. Absolute temporal scotomas in visual field examination are an early sign of Nelson's syndrome. Sufficient hydrocortisone therapy is very important to avoid hypocortisolemia, which stimulates corticotroph cells. Methods of treatment include neurosurgery, radiation therapy and pharmacotherapy. Prognosis in Nelson's syndrome depends on the stage of the disease; it may be poor in invasive pituitary tumors.