Neuroradiology Case of the Week

Case 26

José A. Echeverri, MD, Francisco Garcia-Morales, MD,
and P-L Westesson, MD, PhD, DDS

Clinical Presentation: The patient is a 41-year-old woman, status post bilateral adrenalectomy for Cushing’s disease, who presented with hyperpigmentation.

Radiological Findings
MR Findings: There is 7 x 4 x 4 mm well defined lesion in the pituitary gland, that enhances less than the normal surrounding pituitary gland parenchyma in the dynamic sequence. That corresponds to a microadenoma. The lesion does not deform the pituitary gland (see Figs. 1 & 2).

Figure 1: Coronal dynamic contrast enhanced T1W SE image shows the lesion to be in the mid portion of the gland	Figure 2: Same sequence in the sagittal plane shows the lesion to be located anteriorly within the gland.

Diagnosis:  Pituitary microadenoma, consistent with Nelson’s Syndrome

Discussion:
   Nelson’s syndrome is due to an ACTH-producing pituitary adenoma presenting in patients after bilateral adrenalectomy. ACTH stimulates cutaneous melanocytes with resultant hyperpigmentation [1]. After adrenalectomy, the usual negative feedback from cortisol over the pituitary gland is lost, leading to enlargement of an ACTH-secreting pituitary adenoma [2].

References:

1. Kucharczyk W, Montanera WJ, Becker LE: The Sella Turcica and Parasellar Region. In: Atlas SW ed. Magnetic Resonance Imaging of the Brain and Spine, 2nd edition. Philadelphia, PA: Lippincott-Raven, 1996, 871-930.
2. Gruen JP: Nelson’s Syndrome. www.uscneurosurgery.com, 2000.