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Neuroimaging for the pediatric endocrinologist.

Imaging of the sella and surrounding structures has become essential in the evaluation of pituitary dysfunction and its causes. This article begins with a review of the normal anatomy of the sella and the imaging patterns in and about the normal pituitary gland. There exists considerable variability in the size and configuration of the normal gland in all age groups, and absolute determination of a 'large' or 'small' gland can prove difficult and problematic. Absence of the posterior bright-spot may indicate disruption of the normal stalk transport mechanisms. Microadenomas are well-resolved by magnetic resonance imaging as areas with reduced or delayed enhancement relative to the normal gland. Among hormonally active tumors, adrenocorticotropic hormone-releasing adenomas are most common in the first 11 years of life, while prolactinomas become more common into the teenage years. Macroadenomas tend to present clinically because of mass-effect on adjacent structures, such as the bitemporal hemianopsia seen with optic chiasm compression. Cystic lesions such as Rathke's cleft cysts are commonly seen in the gland, even in healthy children, and their presence need not correlate with any functional abnormality; however, such cysts can cause mass effect on the remaining gland, reflect hemorrhage into adenoma, or actually comprise the central portion of a more worrisome tumor such as craniopharyngioma. Solid tumors of the suprasellar region include optic pathway gliomas, hamartomas, and germinomas. Among inflammatory conditions, granulomatous diseases such as sarcoidosis have predilection for involvement of the suprasellar regions and can spread along perivascular spaces deep within the parenchyma. Because of the association of pituitary endocrinopathies with midline anomalies, one should pay careful attention to midline structures included on a sellar survey.