Value of pituitary gland MRI at 7 T in Cushing's disease and relationship to inferior petrosal sinus sampling: case report

Abstract

Cushing's disease is caused by adrenocorticotrophic hormone (ACTH)-secreting pituitary adenomas, which are often difficult to identify on standard 1.5-T or 3-T MRI, including dynamic contrast imaging. Inferior petrosal and cavernous sinus sampling remains the gold standard for MRI-negative Cushing's disease.The authors report on a 27-year-old woman with Cushing's disease in whom the results of standard 1.5-T and 3-T MRI, including 1.5-T dynamic contrast imaging, were negative. Inferior petrosal sinus sampling showed a high central-to-peripheral ACTH ratio (148:1) as well as a right-to-left ACTH gradient (19:1), suggesting a right-sided pituitary microadenoma. The patient underwent 7-T MRI, which showed evidence of a right-sided pituitary lesion with focal hypoenhancement not visualized on 1.5-T or 3-T MRI. The patient underwent an endoscopic endonasal transsphenoidal operation, with resection of a right-sided pituitary mass. Postoperatively, she developed clinical symptoms suggestive of adrenal insufficiency and a nadir cortisol level of 1.6 μg/dl on postoperative day 3, and hydrocortisone therapy was initiated. Permanent histopathology specimens showed Crooke's hyaline change and ACTH-positive cells suggestive of an adenoma.MRI at 7 T may be beneficial in identifying pituitary microadenoma location in cases of standard 1.5-T and 3-T MRI-negative Cushing's disease. In the future, 7-T MRI may preempt inferior petrosal sinus sampling and help in cases of standard and dynamic contrast 1.5-T and 3-T MRI-negative Cushing's disease.

Keywords: 7-T MRI; ACTH = adrenocorticotropic hormone; Cushing’s disease; GBCA = gadolinium-based contrast agent; IPSS = inferior petrosal sinus sampling; POD = postoperative day; RF = radiofrequency; TSE = turbo spin echo; pituitary surgery.

Figures

FIG. 1.

A: Coronal 1.5-T T2-weighted, precontrast T1-weighted, and postcontrast T1-weighted MR images demonstrating what appears to be a normal pituitary gland. B: Coronal 3-T T2-weighted, precontrast T1 -weighted, and postcontrast T1-weighted MR images also demonstrating what appears to be a normal pituitary gland. C: Coronal 7-T T2-weighted, precontrast T1-weighted, and postcontrast T1-weighted MR images demonstrating what appears to be an 8-mm right-sided hypoenhancing pituitary microadenoma (arrow in right panel), which correlates with the results of IPSS. The 7-T MRI study increased the neurosurgeon’s diagnostic confidence to proceed to surgery. The left side of the sella demonstrates normal enhancing pituitary, and there is some deviation of the pituitary stalk toward the left. The 7-T T2-weighted image clearly demonstrates considerably higher resolution than the 1.5-T and 3-T images.