A novel hook-shaped enhancement on contrast-enhanced sagittal magnetic resonance image in acute Sheehan's syndrome: a case report.

We report characteristic magnetic resonance (MR) image findings in a case of Sheehan's syndrome. A 37-year-old woman experienced complications of retained placenta and massive bleeding (3600 g) during delivery of a full-term baby. A pituitary function test demonstrated panhypopituitarism. MR image of the pituitary gland on postpartum day 10 revealed swelling of the anterior lobe. A hook-shaped enhancement was demonstrated on a sagittal image. The pituitary stalk, majority of the marginal zone of the anterior lobe, the anterior lobe just in front of the posterior lobe, and posterior lobe were well enhanced. In contrast, the central portion and the superior margin, just in front of the stalk insertion of the anterior lobe, were not enhanced. Anatomically, blood supply to these unenhanced portions of the anterior lobe was via the hypophyseal long portal vein and trabecular artery, which are tributaries of the superior hypophyseal artery that originate far from the internal carotid artery. Based on clinical history and MR image findings, the patient was diagnosed with Sheehan's syndrome and treated with hydrocortisone and levothyroxine. Follow-up MR image revealed marked atrophy of the anterior lobe. The characteristic hook-shaped enhancement in Sheehan's syndrome well reflected the vulnerability to massive bleeding based on the complex pituitary vasculature, which has not been reported previously. MR image with contrast enhancement is useful in the diagnosis of the acute phase of Sheehan's syndrome and in evaluating infarction of the anterior lobe.