The Role of CISS Sequence in Evaluating MRI Negative Cushing’s Disease Patients

Purpose: Cushing’s disease is characterized by hypercortisolism due to excess secretion of adrenocorticotropic hormone (ACTH) from pituitary adenoma. Surgical resection of the tumor is the mainstay of management and pre-operative imaging of the pituitary tumor is important for optimizing surgical approach and minimizing complications. However, up to 40% of pituitary adenomas are not detected via standard T1-weighted MRI. Alternative methods include bilateral inferior petrosal sinus sampling (BIPSS) and contrast-enhanced MRI. However, BIPSS is invasive and technically challenging, and the use of contrast dye is contraindicated in patient populations such as those with kidney disease. The purpose of this study is to determine whether Constructive Interference in Steady State (CISS) sequence will be a beneficial adjunct to standard MRI protocol in Cushing’s disease patients. Methods: We retrospectively assessed the ability of CISS sequence MRI in detecting ACTH-secreting pituitary adenomas in 12 patients (11 females and 1 males) diagnosed with Cushing’s disease. All patients underwent transphenoidal pituitary adenomectomy. Two neuroradiologists (reviewer 1, who is a fellow, and reviewer 2, who is an attending) that were blinded to the patients’ clinical history independently reviewed the MR images with three different sequences: T1 without contrast (T1), contrast enhanced T1 (CE-T1), and CISS sequence. Each reviewer was asked to record whether a pituitary adenoma was observable from the images. Localization of pituitary adenomas from MRI results was compared with intraoperative surgical findings. The results of the two neuroradiologists were analyzed and listed independently. Results: ACTH secreting pituitary adenoma was confirmed in 11 of the 12 patients through histopathology. Pituitary samples from one patient were not definitive for adenoma. The sensitivities of the different MRI sequences are shown in Table 1. There was no difference between the sensitivity of CISS sequence and CE-T1 MRI. In two patients, CISS sequence detected pituitary adenomas that were not observed on CE-T1 MR images. The sensitivity increased when the MRI sequences were used in combination to localize pituitary adenomas. When all three MRI sequences were utilized together, the detection rate was 100% (for reviewer 1) and 67% (for reviewer 2). Pituitary adenoma was correctly localized in 73% (reviewer 1) and 71% (reviewer 2) using CISS sequence, 75% (reviewer 1) and 67% (reviewer 2)